Here you will find all scientific publications from the group leader, Daniel Horke. Articles and materials written for a more general audience can be found on the Outreach pages. Recent posters from the group are in the gallery!
Filter Publications:
2024
23.
Abma G L, Parkes M A, Razmus W O, Zhang Y, Wyatt A S, Springate E, Chapman R T, Horke D A, Minns R S
Direct Observation of a Roaming Intermediate and Its Dynamics Journal Article
In: J. Am. Chem. Soc., vol. 146, no. 18, pp. 12595-12600, 2024.
Links | BibTeX | Altmetric | Tags: dynamics, experimental design, HHG, intramolecular interactions, Non-adiabatic dynamics, Photoelectron spectroscopy
@article{doi:10.1021/jacs.4c01543,
title = {Direct Observation of a Roaming Intermediate and Its Dynamics},
author = {Grite L. Abma and Michael A. Parkes and Weronika O. Razmus and Yu Zhang and Adam S. Wyatt and Emma Springate and Richard T. Chapman and Daniel A. Horke and Russell S. Minns},
doi = {10.1021/jacs.4c01543},
year = {2024},
date = {2024-04-29},
urldate = {2024-04-29},
journal = {J. Am. Chem. Soc.},
volume = {146},
number = {18},
pages = {12595-12600},
keywords = {dynamics, experimental design, HHG, intramolecular interactions, Non-adiabatic dynamics, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
22.
Abma G L, Parkes M A, Horke D A
Preparation of Tautomer-Pure Molecular Beams by Electrostatic Deflection Journal Article
In: J. Phys. Chem. Lett., vol. 15, no. 17, pp. 4587-4592, 2024.
Links | BibTeX | Altmetric | Tags: Control, electrostatic deflector, experimental design, Isomer-effects, photoelectron imaging, Photoelectron spectroscopy
@article{doi:10.1021/acs.jpclett.4c00768,
title = {Preparation of Tautomer-Pure Molecular Beams by Electrostatic Deflection},
author = {Grite L. Abma and Michael A. Parkes and Daniel A. Horke},
doi = {10.1021/acs.jpclett.4c00768},
year = {2024},
date = {2024-04-24},
urldate = {2024-04-24},
journal = {J. Phys. Chem. Lett.},
volume = {15},
number = {17},
pages = {4587-4592},
keywords = {Control, electrostatic deflector, experimental design, Isomer-effects, photoelectron imaging, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
2023
21.
Caballo A, Huits A J T M, Parker D H, Horke D A
Disentangling Multiphoton Ionization and Dissociation Channels in Molecular Oxygen Using Photoelectron–Photoion Coincidence Imaging Journal Article
In: J. Phys. Chem. A, vol. 127, no. 1, pp. 92–98, 2023, ISSN: 1089-5639, 1520-5215.
Abstract | Links | BibTeX | Altmetric | Tags: Coincidence Imaging, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{caballoDisentanglingMultiphotonIonization2023,
title = {Disentangling Multiphoton Ionization and Dissociation Channels in Molecular Oxygen Using Photoelectron\textendashPhotoion Coincidence Imaging},
author = {Ana Caballo and Anders J. T. M. Huits and David H. Parker and Daniel A. Horke},
url = {https://pubs.acs.org/doi/10.1021/acs.jpca.2c06707},
doi = {10.1021/acs.jpca.2c06707},
issn = {1089-5639, 1520-5215},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {J. Phys. Chem. A},
volume = {127},
number = {1},
pages = {92--98},
abstract = {Multiphoton excitation of molecular oxygen in the 392-408 nm region is studied using a tunable femtosecond laser coupled with a double velocity map imaging photoelectron- photoion coincidence spectrometer. The laser intensity is held at $\leqsim$1 TW/cm2 to ensure excitation in the perturbative regime, where the possibility of resonance enhanced multiphoton ionization (REMPI) can be investigated. O2+ production is found to be resonance enhanced around 400 nm via three-photon excitation to the e$'$3$Delta$u(v = 0) state, similar to results from REMPI studies using nanosecond dye lasers. O+ production reaches 7% of the total ion yield around 405 nm due to two processes: autoionization following five-photon excitation of O2, producing O2+(X(v)) in a wide range of vibrational states followed by two- or three-photon dissociation, or six-photon excitation to a superexcited O2** state followed by neutral dissociation and subsequent ionization of the electronically excited O atom. Coincidence detection is shown to be crucial in identifying these competing pathways.},
keywords = {Coincidence Imaging, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
Multiphoton excitation of molecular oxygen in the 392-408 nm region is studied using a tunable femtosecond laser coupled with a double velocity map imaging photoelectron- photoion coincidence spectrometer. The laser intensity is held at $łeqsim$1 TW/cm2 to ensure excitation in the perturbative regime, where the possibility of resonance enhanced multiphoton ionization (REMPI) can be investigated. O2+ production is found to be resonance enhanced around 400 nm via three-photon excitation to the e$’$3$Delta$u(v = 0) state, similar to results from REMPI studies using nanosecond dye lasers. O+ production reaches 7% of the total ion yield around 405 nm due to two processes: autoionization following five-photon excitation of O2, producing O2+(X(v)) in a wide range of vibrational states followed by two- or three-photon dissociation, or six-photon excitation to a superexcited O2** state followed by neutral dissociation and subsequent ionization of the electronically excited O atom. Coincidence detection is shown to be crucial in identifying these competing pathways.
2021
20.
Caballo A, Huits A J T M, Vredenborg A, Balster M, Parker D H, Horke D A
Femtosecond 2 + 1 Resonance-Enhanced Multiphoton Ionization Spectroscopy of the C-State in Molecular Oxygen Journal Article
In: J. Phys. Chem. A, vol. 125, no. 41, pp. 9060–9064, 2021, ISSN: 1089-5639.
Abstract | Links | BibTeX | Altmetric | Tags: Coincidence Imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Caballo:J.Phys.Chem.A125:9060,
title = {Femtosecond 2 + 1 Resonance-Enhanced Multiphoton Ionization Spectroscopy of the C-State in Molecular Oxygen},
author = {Ana Caballo and Anders J. T. M. Huits and Arno Vredenborg and Michiel Balster and David H. Parker and Daniel A. Horke},
url = {https://doi.org/10.1021/acs.jpca.1c05541},
doi = {10.1021/acs.jpca.1c05541},
issn = {1089-5639},
year = {2021},
date = {2021-10-01},
journal = {J. Phys. Chem. A},
volume = {125},
number = {41},
pages = {9060--9064},
publisher = {American Chemical Society},
abstract = {Coincidence electron-cation imaging is used to characterize the multiphoton ionization of O2 via the v = 4,5 levels of the 3s(3$Pi$g) Rydberg state. A tunable 100 fs laser beam operating in the 271\textendash 263 nm region is found to cause a nonresonant ionization across this wavelength range, with an additional resonant ionization channel only observed when tuned to the 3$Pi$g(v = 5) level. A distinct 3s textrightarrow p wave character is observed in the photoelectron angular distribution for the v = 5 channel when on resonance.},
keywords = {Coincidence Imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
Coincidence electron-cation imaging is used to characterize the multiphoton ionization of O2 via the v = 4,5 levels of the 3s(3$Pi$g) Rydberg state. A tunable 100 fs laser beam operating in the 271– 263 nm region is found to cause a nonresonant ionization across this wavelength range, with an additional resonant ionization channel only observed when tuned to the 3$Pi$g(v = 5) level. A distinct 3s textrightarrow p wave character is observed in the photoelectron angular distribution for the v = 5 channel when on resonance.
19.
Warne E M, Smith A D, Horke D A, Springate E, Jones A J H, Cacho C, Chapman R T, Minns R S
Time Resolved Detection of the S(1D) Product of the UV Induced Dissociation of CS2 Journal Article
In: J. Chem. Phys., vol. 154, no. 3, pp. 034302, 2021, ISSN: 0021-9606, 1089-7690.
Abstract | Links | BibTeX | Altmetric | Tags: Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy
@article{Warne:J.Chem.Phys.154:034302,
title = {Time Resolved Detection of the S(1D) Product of the UV Induced Dissociation of CS2},
author = {Emily M. Warne and Adam D. Smith and Daniel A. Horke and Emma Springate and Alfred J. H. Jones and Cephise Cacho and Richard T. Chapman and Russell S. Minns},
url = {http://aip.scitation.org/doi/10.1063/5.0035045},
doi = {10.1063/5.0035045},
issn = {0021-9606, 1089-7690},
year = {2021},
date = {2021-01-01},
urldate = {2021-06-21},
journal = {J. Chem. Phys.},
volume = {154},
number = {3},
pages = {034302},
abstract = {The products formed following the photodissociation of UV (200 nm) excited CS2 are monitored in a time resolved photoelectron spectroscopy experiment using femtosecond XUV (21.5 eV) photons. By spectrally resolving the electrons, we identify separate photoelectron bands related to the CS2 + h$nu$ textrightarrow S(1D) + CS and CS2 + h$nu$ textrightarrow S(3P) + CS dissociation channels, which show different appearance and rise times. The measurements show that there is no delay in the appearance of the S(1D) product contrary to the results of Horio et al. [J. Chem. Phys. 147, 013932 (2017)]. Analysis of the photoelectron yield associated with the atomic products allows us to obtain a S(3P)/S(1D) branching ratio and the rate constants associated with dissociation and intersystem crossing rather than the effective lifetime observed through the measurement of excited state populations alone.},
keywords = {Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
The products formed following the photodissociation of UV (200 nm) excited CS2 are monitored in a time resolved photoelectron spectroscopy experiment using femtosecond XUV (21.5 eV) photons. By spectrally resolving the electrons, we identify separate photoelectron bands related to the CS2 + h$nu$ textrightarrow S(1D) + CS and CS2 + h$nu$ textrightarrow S(3P) + CS dissociation channels, which show different appearance and rise times. The measurements show that there is no delay in the appearance of the S(1D) product contrary to the results of Horio et al. [J. Chem. Phys. 147, 013932 (2017)]. Analysis of the photoelectron yield associated with the atomic products allows us to obtain a S(3P)/S(1D) branching ratio and the rate constants associated with dissociation and intersystem crossing rather than the effective lifetime observed through the measurement of excited state populations alone.
2018
18.
Smith A D, Warne E M, Bellshaw D, Horke D A, Tudorovskya M, Springate E, Jones A J H, Cacho C, Chapman R T, Kirrander A, Minns R S
Mapping the Complete Reaction Path of a Complex Photochemical Reaction Journal Article
In: Phys. Rev. Lett., vol. 120, no. 18, pp. 183003, 2018.
Abstract | Links | BibTeX | Altmetric | Tags: Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy
@article{Smith:Phys.Rev.Lett.120:183003,
title = {Mapping the Complete Reaction Path of a Complex Photochemical Reaction},
author = {Adam D. Smith and Emily M. Warne and Darren Bellshaw and Daniel A. Horke and Maria Tudorovskya and Emma Springate and Alfred J. H. Jones and Cephise Cacho and Richard T. Chapman and Adam Kirrander and Russell S. Minns},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.120.183003},
doi = {10.1103/PhysRevLett.120.183003},
year = {2018},
date = {2018-05-01},
urldate = {2019-01-24},
journal = {Phys. Rev. Lett.},
volume = {120},
number = {18},
pages = {183003},
abstract = {We probe the dynamics of dissociating CS2 molecules across the entire reaction pathway upon excitation. Photoelectron spectroscopy measurements using laboratory-generated femtosecond extreme ultraviolet pulses monitor the competing dissociation, internal conversion, and intersystem crossing dynamics. Dissociation occurs either in the initially excited singlet manifold or, via intersystem crossing, in the triplet manifold. Both product channels are monitored and show that, despite being more rapid, the singlet dissociation is the minor product and that triplet state products dominate the final yield. We explain this by a consideration of accurate potential energy curves for both the singlet and triplet states. We propose that rapid internal conversion stabilizes the singlet population dynamically, allowing for singlet-triplet relaxation via intersystem crossing and the efficient formation of spin-forbidden dissociation products on longer timescales. The study demonstrates the importance of measuring the full reaction pathway for defining accurate reaction mechanisms.},
keywords = {Coincidence Imaging, dynamics, HHG, Non-adiabatic dynamics, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
We probe the dynamics of dissociating CS2 molecules across the entire reaction pathway upon excitation. Photoelectron spectroscopy measurements using laboratory-generated femtosecond extreme ultraviolet pulses monitor the competing dissociation, internal conversion, and intersystem crossing dynamics. Dissociation occurs either in the initially excited singlet manifold or, via intersystem crossing, in the triplet manifold. Both product channels are monitored and show that, despite being more rapid, the singlet dissociation is the minor product and that triplet state products dominate the final yield. We explain this by a consideration of accurate potential energy curves for both the singlet and triplet states. We propose that rapid internal conversion stabilizes the singlet population dynamically, allowing for singlet-triplet relaxation via intersystem crossing and the efficient formation of spin-forbidden dissociation products on longer timescales. The study demonstrates the importance of measuring the full reaction pathway for defining accurate reaction mechanisms.
2017
17.
Bellshaw D, Horke D A, Smith A D, Watts H M, Jager E, Springate E, Alexander O, Cacho C, Chapman R T, Kirrander A, Minns R S
Ab-Initio Surface Hopping and Multiphoton Ionisation Study of the Photodissociation Dynamics of CS2 Journal Article
In: Chem. Phys. Lett., vol. 683, pp. 383–388, 2017, ISSN: 0009-2614.
Abstract | Links | BibTeX | Altmetric | Tags: dynamics, Non-adiabatic dynamics, Photoelectron spectroscopy, velocity-map imaging
@article{Bellshaw:Chem.Phys.Lett.683:383,
title = {Ab-Initio Surface Hopping and Multiphoton Ionisation Study of the Photodissociation Dynamics of CS2},
author = {Darren Bellshaw and Daniel A. Horke and Adam D. Smith and Hannah M. Watts and Edward Jager and Emma Springate and Oliver Alexander and Cephise Cacho and Richard T. Chapman and Adam Kirrander and Russell S. Minns},
url = {http://www.sciencedirect.com/science/article/pii/S0009261417301744},
doi = {10.1016/j.cplett.2017.02.058},
issn = {0009-2614},
year = {2017},
date = {2017-09-01},
urldate = {2019-01-24},
journal = {Chem. Phys. Lett.},
volume = {683},
pages = {383--388},
series = {Ahmed Zewail (1946-2016) Commemoration Issue of Chemical Physics Letters},
abstract = {New ab initio surface hopping simulations of the excited state dynamics of CS2 including spin-orbit coupling are compared to new experimental measurements using a multiphoton ionisation probe in a photoelectron spectroscopy experiment. The calculations highlight the importance of the triplet states even in the very early time dynamics of the dissociation process and allow us to unravel the signatures in the experimental spectrum, linking the observed changes to both electronic and nuclear degrees of freedom within the molecule.},
keywords = {dynamics, Non-adiabatic dynamics, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
New ab initio surface hopping simulations of the excited state dynamics of CS2 including spin-orbit coupling are compared to new experimental measurements using a multiphoton ionisation probe in a photoelectron spectroscopy experiment. The calculations highlight the importance of the triplet states even in the very early time dynamics of the dissociation process and allow us to unravel the signatures in the experimental spectrum, linking the observed changes to both electronic and nuclear degrees of freedom within the molecule.
2016
16.
Horke D A, Watts H M, Smith A D, Jager E, Springate E, Alexander O, Cacho C, Chapman R T, Minns R S
Hydrogen Bonds in Excited State Proton Transfer Journal Article
In: Phys. Rev. Lett., vol. 117, no. 16, pp. 163002, 2016.
Abstract | Links | BibTeX | Altmetric | Tags: Coincidence Imaging, intramolecular interactions, Isomer-effects, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Horke:Phys.Rev.Lett.117:163002,
title = {Hydrogen Bonds in Excited State Proton Transfer},
author = {D A Horke and H M Watts and A D Smith and E Jager and E Springate and O Alexander and C Cacho and R T Chapman and R S Minns},
url = {http://link.aps.org/doi/10.1103/PhysRevLett.117.163002},
doi = {10.1103/PhysRevLett.117.163002},
year = {2016},
date = {2016-10-01},
journal = {Phys. Rev. Lett.},
volume = {117},
number = {16},
pages = {163002},
abstract = {Hydrogen bonding may safeguard biomolecules against the damaging effects of UV light.},
keywords = {Coincidence Imaging, intramolecular interactions, Isomer-effects, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
Hydrogen bonding may safeguard biomolecules against the damaging effects of UV light.
15.
Smith A D, Watts H M, Jager E, Horke D A, Springate E, Alexander O, Cacho C, Chapman R T, Minns R S
Resonant Multiphoton Ionisation Probe of the Photodissociation Dynamics of Ammonia Journal Article
In: Phys. Chem. Chem. Phys., vol. 18, no. 40, pp. 28150–28156, 2016.
Abstract | Links | BibTeX | Altmetric | Tags: dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Smith:Phys.Chem.Chem.Phys.18:28150,
title = {Resonant Multiphoton Ionisation Probe of the Photodissociation Dynamics of Ammonia},
author = {Adam D Smith and Hannah M Watts and Edward Jager and Daniel A Horke and Emma Springate and Oliver Alexander and Cephise Cacho and Richard T Chapman and Russell S Minns},
url = {http://pubs.rsc.org/en/content/articlehtml/2016/cp/c6cp05279g},
doi = {10.1039/C6CP05279G},
year = {2016},
date = {2016-10-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {18},
number = {40},
pages = {28150--28156},
abstract = {The dissociation dynamics of the ~A-state of ammonia have been studied using a resonant multiphoton ionisation probe in a photoelectron spectroscopy experiment. The use of a resonant intermediate in the multiphoton ionisation process changes the ionisation propensity, allowing access to different ion states when compared with equivalent single photon ionisation experiments. Ionisation through the E$'$ 1A1$'$ Rydberg intermediate means we maintain overlap with the ion state for an extended period, allowing us to monitor the excited state population for several hundred femtoseconds. The vibrational states in the photoelectron spectrum show two distinct timescales, 200 fs and 320 fs, that we assign to the non-adiabatic and adiabatic dissociation processes respectively. The different timescales derive from differences in the wavepacket trajectories for the two dissociation pathways that resonantly excite different vibrational states in the intermediate Rydberg state. The timescales are similar to those obtained from time resolved ion kinetic energy release measurements, suggesting we can measure the different trajectories taken out to the region of conical intersection.},
keywords = {dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The dissociation dynamics of the ~A-state of ammonia have been studied using a resonant multiphoton ionisation probe in a photoelectron spectroscopy experiment. The use of a resonant intermediate in the multiphoton ionisation process changes the ionisation propensity, allowing access to different ion states when compared with equivalent single photon ionisation experiments. Ionisation through the E$’$ 1A1$’$ Rydberg intermediate means we maintain overlap with the ion state for an extended period, allowing us to monitor the excited state population for several hundred femtoseconds. The vibrational states in the photoelectron spectrum show two distinct timescales, 200 fs and 320 fs, that we assign to the non-adiabatic and adiabatic dissociation processes respectively. The different timescales derive from differences in the wavepacket trajectories for the two dissociation pathways that resonantly excite different vibrational states in the intermediate Rydberg state. The timescales are similar to those obtained from time resolved ion kinetic energy release measurements, suggesting we can measure the different trajectories taken out to the region of conical intersection.
2015
14.
Horke D A, Chatterley A S, Bull J N, Verlet J R R
Time-Resolved Photodetachment Anisotropy: Gas-Phase Rotational and Vibrational Dynamics of the Fluorescein Anion Journal Article
In: J. Phys. Chem. Lett., vol. 6, no. 1, pp. 189–194, 2015.
Abstract | Links | BibTeX | Altmetric | Tags: alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Horke:J.Phys.Chem.Lett.6:189,
title = {Time-Resolved Photodetachment Anisotropy: Gas-Phase Rotational and Vibrational Dynamics of the Fluorescein Anion},
author = {Daniel A Horke and Adam S Chatterley and James N Bull and Jan R R Verlet},
url = {http://pubs.acs.org/doi/abs/10.1021/jz5022526},
doi = {10.1021/jz5022526},
year = {2015},
date = {2015-01-01},
journal = {J. Phys. Chem. Lett.},
volume = {6},
number = {1},
pages = {189--194},
abstract = {The photoelectron signal of the singly deprotonated fluorescein anion is found to be highly dependent on the relative polarization between pump and probe pulses, and time-resolved photodetachment anisotropy (TR-PA) is developed as a probe of the rotational dynamics of the chromophore. The total photoelectron signal shows both rotational and vibrational wavepacket dynamics, and we demonstrate how TR-PA can readily disentangle these dynamical processes. TR-PA in fluorescein presents specific opportunities for its development as a probe for rotational dynamics in large biomolecules as fluorescein derivatives are commonly incorporated in complex biomolecules and have been used extensively in time-resolved fluorescence anisotropy measurements, to which TR-PA is a gas-phase analogue.},
keywords = {alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The photoelectron signal of the singly deprotonated fluorescein anion is found to be highly dependent on the relative polarization between pump and probe pulses, and time-resolved photodetachment anisotropy (TR-PA) is developed as a probe of the rotational dynamics of the chromophore. The total photoelectron signal shows both rotational and vibrational wavepacket dynamics, and we demonstrate how TR-PA can readily disentangle these dynamical processes. TR-PA in fluorescein presents specific opportunities for its development as a probe for rotational dynamics in large biomolecules as fluorescein derivatives are commonly incorporated in complex biomolecules and have been used extensively in time-resolved fluorescence anisotropy measurements, to which TR-PA is a gas-phase analogue.
2014
13.
Chatterley A S, Horke D A, Verlet J R R
Effects of Resonant Excitation, Pulse Duration and Intensity on Photoelectron Imaging of a Dianion Journal Article
In: Phys. Chem. Chem. Phys., vol. 16, no. 2, pp. 489–496, 2014.
Abstract | Links | BibTeX | Altmetric | Tags: Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging
@article{Chatterley:Phys.Chem.Chem.Phys.16:489,
title = {Effects of Resonant Excitation, Pulse Duration and Intensity on Photoelectron Imaging of a Dianion},
author = {Adam S Chatterley and Daniel A Horke and Jan R R Verlet},
url = {http://xlink.rsc.org/?DOI=c3cp53235f},
doi = {10.1039/c3cp53235f},
year = {2014},
date = {2014-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {16},
number = {2},
pages = {489--496},
abstract = {The photoelectron imaging of the indigo carmine dianion is used to demonstrate the effects of resonance excitation, pulse duration and pulse intensity on the photoelectron spectra and angular distributions of a dianion. Excitation of the S1 state leads to an aligned distribution of excited state dianions. The photoelectron angular distribution following subsequent photodetachment within a femtosecond laser pulse is primarily determined by the repulsive Coulomb barrier. Extending the timescale for photodetachment to nanoseconds leads to dramatic changes in both the spectral and angular distributions. These observations are explained in terms of statistical detachment of electrons, either from the monoanion, or from the ground state of the dianion following a number of photon cycles through the S1 $\leftarrow$ S0 transition. At high intensity, new electron emission channels open up, leading to emission below the repulsive Coulomb barrier. This has been assigned to strong-field induced detachment and the effect of an electric field on the Coulomb barrier is discussed in terms of the photoelectron spectra and angular distributions.},
keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The photoelectron imaging of the indigo carmine dianion is used to demonstrate the effects of resonance excitation, pulse duration and pulse intensity on the photoelectron spectra and angular distributions of a dianion. Excitation of the S1 state leads to an aligned distribution of excited state dianions. The photoelectron angular distribution following subsequent photodetachment within a femtosecond laser pulse is primarily determined by the repulsive Coulomb barrier. Extending the timescale for photodetachment to nanoseconds leads to dramatic changes in both the spectral and angular distributions. These observations are explained in terms of statistical detachment of electrons, either from the monoanion, or from the ground state of the dianion following a number of photon cycles through the S1 $łeftarrow$ S0 transition. At high intensity, new electron emission channels open up, leading to emission below the repulsive Coulomb barrier. This has been assigned to strong-field induced detachment and the effect of an electric field on the Coulomb barrier is discussed in terms of the photoelectron spectra and angular distributions.
12.
Verlet J R R, Horke D A, Chatterley A S
Excited States of Multiply-Charged Anions Probed by Photoelectron Imaging: Riding the Repulsive Coulomb Barrier Journal Article
In: Phys. Chem. Chem. Phys., vol. 16, no. 29, pp. 15043–15052, 2014.
Abstract | Links | BibTeX | Altmetric | Tags: Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, review
@article{Verlet:Phys.Chem.Chem.Phys.16:15043,
title = {Excited States of Multiply-Charged Anions Probed by Photoelectron Imaging: Riding the Repulsive Coulomb Barrier},
author = {Jan R R Verlet and Daniel A Horke and Adam S Chatterley},
url = {http://xlink.rsc.org/?DOI=c4cp01667j},
doi = {10.1039/c4cp01667j},
year = {2014},
date = {2014-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {16},
number = {29},
pages = {15043--15052},
abstract = {Many properties of isolated multiply-charged anions (MCAs) are dictated by the strong intra-molecular Coulomb interactions that are present. The most striking property of MCAs is a long-range repulsive Coulomb barrier (RCB) that arises from the repulsive interaction between an electron and an anion which must be overcome to form a MCA. Excited states provide a route to probing this RCB and the focus of this Perspective is on recent photoelectron experiments, including angularly and temporally resolved, that have provided detailed physical insight into the RCB surfaces, their anisotropy, and their use to monitor molecular dynamics in real-time. An outlook provides some future prospects that studies on MCAs provide in terms of monitoring structural, charge-migration, and solvation dynamics.},
keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, review},
pubstate = {published},
tppubtype = {article}
}
Many properties of isolated multiply-charged anions (MCAs) are dictated by the strong intra-molecular Coulomb interactions that are present. The most striking property of MCAs is a long-range repulsive Coulomb barrier (RCB) that arises from the repulsive interaction between an electron and an anion which must be overcome to form a MCA. Excited states provide a route to probing this RCB and the focus of this Perspective is on recent photoelectron experiments, including angularly and temporally resolved, that have provided detailed physical insight into the RCB surfaces, their anisotropy, and their use to monitor molecular dynamics in real-time. An outlook provides some future prospects that studies on MCAs provide in terms of monitoring structural, charge-migration, and solvation dynamics.
2013
11.
Horke D A, Li Q, Blancafort L A, Verlet J R R
Ultrafast Above-Threshold Dynamics of the Radical Anion of a Prototypical Quinone Electron-Acceptor Journal Article
In: Nature Chem., vol. 5, no. 8, pp. 711–717, 2013.
Links | BibTeX | Altmetric | Tags: dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Horke:NatureChem.5:711,
title = {Ultrafast Above-Threshold Dynamics of the Radical Anion of a Prototypical Quinone Electron-Acceptor},
author = {Daniel A Horke and Quansong Li and Llu A Blancafort and Jan R R Verlet},
url = {http://dx.doi.org/10.1038/nchem.1705},
doi = {10.1038/nchem.1705},
year = {2013},
date = {2013-09-01},
urldate = {2013-09-01},
journal = {Nature Chem.},
volume = {5},
number = {8},
pages = {711--717},
keywords = {dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
10.
Horke D A, Chatterley A S, Verlet J R R
Influence of the Repulsive Coulomb Barrier on Photoelectron Spectra and Angular Distributions in a Resonantly Excited Dianion Journal Article
In: J. Chem. Phys., vol. 139, no. 8, pp. 084302–10, 2013.
Links | BibTeX | Altmetric | Tags: Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging
@article{Horke:J.Chem.Phys.139:084302,
title = {Influence of the Repulsive Coulomb Barrier on Photoelectron Spectra and Angular Distributions in a Resonantly Excited Dianion},
author = {Daniel A Horke and Adam S Chatterley and Jan R R Verlet},
url = {http://dx.doi.org/10.1063/1.4818597},
doi = {10.1063/1.4818597},
year = {2013},
date = {2013-01-01},
journal = {J. Chem. Phys.},
volume = {139},
number = {8},
pages = {084302--10},
keywords = {Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
9.
Mooney C R S, Horke D A, Chatterley A S, Simperler A, Fielding H H, Verlet J R R
Taking the Green Fluorescence out of the Protein: Dynamics of the Isolated GFP Chromophore Anion Journal Article
In: Chem. Sci., vol. 4, no. 3, pp. 921, 2013.
Links | BibTeX | Altmetric | Tags: Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Mooney:Chem.Sci.4:921,
title = {Taking the Green Fluorescence out of the Protein: Dynamics of the Isolated GFP Chromophore Anion},
author = {Ciar\'{a}n R S Mooney and Daniel A Horke and Adam S Chatterley and Alexandra Simperler and Helen H Fielding and Jan R R Verlet},
url = {http://xlink.rsc.org/?DOI=c2sc21737f},
doi = {10.1039/c2sc21737f},
year = {2013},
date = {2013-01-01},
journal = {Chem. Sci.},
volume = {4},
number = {3},
pages = {921},
keywords = {Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
2012
8.
Horke D A, Chatterley A S, Verlet J R R
Femtosecond Photoelectron Imaging of Aligned Polyanions: Probing Molecular Dynamics through the Electron–Anion Coulomb Repulsion Journal Article
In: J. Phys. Chem. Lett., vol. 3, no. 7, pp. 834–838, 2012, ISSN: 1948-7185.
Abstract | Links | BibTeX | Altmetric | Tags: alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Horke:J.Phys.Chem.Lett.3:834,
title = {Femtosecond Photoelectron Imaging of Aligned Polyanions: Probing Molecular Dynamics through the Electron\textendashAnion Coulomb Repulsion},
author = {Daniel. A. Horke and Adam S. Chatterley and Jan R. R. Verlet},
url = {https://doi.org/10.1021/jz3000933},
doi = {10.1021/jz3000933},
issn = {1948-7185},
year = {2012},
date = {2012-04-01},
urldate = {2019-04-03},
journal = {J. Phys. Chem. Lett.},
volume = {3},
number = {7},
pages = {834--838},
abstract = {The first time-resolved photoelectron imaging study of a polyanion is presented. Using the alignment induced through resonance excitation, the photoelectron angular distributions can be qualitatively understood in terms of the position of localized excess charges on the molecular skeleton, which influence the photoemission dynamics. Pump\textendash probe experiments are used to demonstrate that the photoelectron angular distribution is also sensitive to molecular dynamics. This is shown here for the rotational dynamics of a polyanion, in which the photoelectron anisotropy tracks the rotational coherence as it dephases. The methodology can in principle be applied to general molecular dynamics in large polyanions, providing a new route to studying ultrafast structural dynamics in complex gas-phase systems.},
keywords = {alignment, Anion spectroscopy, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The first time-resolved photoelectron imaging study of a polyanion is presented. Using the alignment induced through resonance excitation, the photoelectron angular distributions can be qualitatively understood in terms of the position of localized excess charges on the molecular skeleton, which influence the photoemission dynamics. Pump– probe experiments are used to demonstrate that the photoelectron angular distribution is also sensitive to molecular dynamics. This is shown here for the rotational dynamics of a polyanion, in which the photoelectron anisotropy tracks the rotational coherence as it dephases. The methodology can in principle be applied to general molecular dynamics in large polyanions, providing a new route to studying ultrafast structural dynamics in complex gas-phase systems.
7.
Horke D A, Chatterley A S, Verlet J R R
Effect of Internal Energy on the Repulsive Coulomb Barrier of Polyanions Journal Article
In: Phys. Rev. Lett., vol. 108, no. 8, pp. 083003, 2012.
Links | BibTeX | Altmetric | Tags: photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging
@article{Horke:Phys.Rev.Lett.108:083003,
title = {Effect of Internal Energy on the Repulsive Coulomb Barrier of Polyanions},
author = {Daniel A Horke and Adam S Chatterley and Jan R R Verlet},
url = {http://link.aps.org/doi/10.1103/PhysRevLett.108.083003},
doi = {10.1103/PhysRevLett.108.083003},
year = {2012},
date = {2012-02-01},
journal = {Phys. Rev. Lett.},
volume = {108},
number = {8},
pages = {083003},
keywords = {photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
6.
Chatterley A S, Horke D A, Verlet J R R
On the Intrinsic Photophysics of Indigo: A Time-Resolved Photoelectron Spectroscopy Study of the Indigo Carmine Dianion Journal Article
In: Phys. Chem. Chem. Phys., vol. 14, no. 46, pp. 16155, 2012.
Links | BibTeX | Altmetric | Tags: Anion spectroscopy, dynamics, Photoelectron spectroscopy, polyanions, velocity-map imaging
@article{Chatterley:Phys.Chem.Chem.Phys.14:16155,
title = {On the Intrinsic Photophysics of Indigo: A Time-Resolved Photoelectron Spectroscopy Study of the Indigo Carmine Dianion},
author = {Adam S Chatterley and Daniel A Horke and Jan R R Verlet},
url = {http://xlink.rsc.org/?DOI=c2cp43275g},
doi = {10.1039/c2cp43275g},
year = {2012},
date = {2012-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {14},
number = {46},
pages = {16155},
keywords = {Anion spectroscopy, dynamics, Photoelectron spectroscopy, polyanions, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
5.
Horke D A, Verlet J R R
Photoelectron Spectroscopy of the Model GFP Chromophore Anion Journal Article
In: Phys. Chem. Chem. Phys., vol. 14, no. 24, pp. 8511–8515, 2012.
Abstract | Links | BibTeX | Altmetric | Tags: Anion spectroscopy, Photoelectron spectroscopy
@article{Horke:Phys.Chem.Chem.Phys.14:8511,
title = {Photoelectron Spectroscopy of the Model GFP Chromophore Anion},
author = {Daniel A Horke and Jan R R Verlet},
url = {http://xlink.rsc.org/?DOI=c2cp40880e},
doi = {10.1039/c2cp40880e},
year = {2012},
date = {2012-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {14},
number = {24},
pages = {8511--8515},
abstract = {A photoelectron spectroscopy study of the anionic model chromophore of the green fluorescent protein is presented. From the photoelectron spectra taken at 3.496 eV, 4.62 eV, and 6.15 eV the vertical and adiabatic detachment energies are determined to be 2.8 +/- 0.1 eV and 2.6 +/- 0.2 eV, respectively. The vertical detachment energy is higher than the S1 ? S0 absorption maximum (2.57 eV) and indicates that the S1 state is bound with respect to electron detachment in the Franck-Condon region. The photoelectron spectrum taken at 6.15 eV, together with TD-DFT calculations, are used to assign a number of excited states in the neutral radical that correspond to electron loss from occupied orbitals in the anion. The photoelectron spectrum at 2.58 eV shows evidence for electrons formed by thermionic emission, suggesting that internal conversion is the dominant relaxation pathway following S1 ? S0 excitation.},
keywords = {Anion spectroscopy, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
A photoelectron spectroscopy study of the anionic model chromophore of the green fluorescent protein is presented. From the photoelectron spectra taken at 3.496 eV, 4.62 eV, and 6.15 eV the vertical and adiabatic detachment energies are determined to be 2.8 +/- 0.1 eV and 2.6 +/- 0.2 eV, respectively. The vertical detachment energy is higher than the S1 ? S0 absorption maximum (2.57 eV) and indicates that the S1 state is bound with respect to electron detachment in the Franck-Condon region. The photoelectron spectrum taken at 6.15 eV, together with TD-DFT calculations, are used to assign a number of excited states in the neutral radical that correspond to electron loss from occupied orbitals in the anion. The photoelectron spectrum at 2.58 eV shows evidence for electrons formed by thermionic emission, suggesting that internal conversion is the dominant relaxation pathway following S1 ? S0 excitation.
4.
Horke D A
Femtosecond Photoelectron Imaging of Anions PhD Thesis
2012.
Links | BibTeX | Tags: alignment, Anion spectroscopy, experimental design, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging
@phdthesis{Horke:undefined:,
title = {Femtosecond Photoelectron Imaging of Anions},
author = {Daniel A Horke},
url = {http://etheses.dur.ac.uk/5950/},
year = {2012},
date = {2012-01-01},
address = {Durham},
keywords = {alignment, Anion spectroscopy, experimental design, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, polyanions, velocity-map imaging},
pubstate = {published},
tppubtype = {phdthesis}
}
2011
3.
Horke D A, Roberts G M, Verlet J R R
Excited States in Electron-Transfer Reaction Products: Ultrafast Relaxation Dynamics of an Isolated Acceptor Radical Anion Journal Article
In: J. Phys. Chem. A, vol. 115, no. 30, pp. 8369–8374, 2011.
Links | BibTeX | Altmetric | Tags: Anion spectroscopy, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy
@article{Horke:J.Phys.Chem.A115:8369,
title = {Excited States in Electron-Transfer Reaction Products: Ultrafast Relaxation Dynamics of an Isolated Acceptor Radical Anion},
author = {Daniel A Horke and Gareth M Roberts and Jan R R Verlet},
url = {http://dx.doi.org/10.1021/jp2038202},
doi = {10.1021/jp2038202},
year = {2011},
date = {2011-01-01},
urldate = {2011-01-01},
journal = {J. Phys. Chem. A},
volume = {115},
number = {30},
pages = {8369--8374},
keywords = {Anion spectroscopy, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy},
pubstate = {published},
tppubtype = {article}
}
2.
Horke D A, Verlet J R R
Time-Resolved Photoelectron Imaging of the Chloranil Radical Anion: Ultrafast Relaxation of Electronically Excited Electron Acceptor States Journal Article
In: Phys. Chem. Chem. Phys., vol. 13, no. 43, pp. 19546–19552, 2011.
Abstract | Links | BibTeX | Altmetric | Tags: Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Horke:Phys.Chem.Chem.Phys.13:19546,
title = {Time-Resolved Photoelectron Imaging of the Chloranil Radical Anion: Ultrafast Relaxation of Electronically Excited Electron Acceptor States},
author = {Daniel A Horke and Jan R R Verlet},
url = {http://xlink.rsc.org/?DOI=c1cp22237f},
doi = {10.1039/c1cp22237f},
year = {2011},
date = {2011-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {13},
number = {43},
pages = {19546--19552},
abstract = {The spectroscopy and dynamics of near-threshold excited states of the isolated chloranil radical anion are investigated using photoelectron imaging. The photoelectron images taken at 480 nm clearly indicate resonance-enhanced photodetachment via a bound electronic excited state. Time-resolved photoelectron imaging reveals that the excited state rapidly decays on a timescale of 130 fs via internal conversion. The ultrafast relaxation dynamics of excited states near threshold are pertinent to common electron acceptor molecules based on the quinone moiety and may serve as doorway states that enable efficient electron transfer in the highly exergonic inverted regime, despite the presence of large free energy barriers.},
keywords = {Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The spectroscopy and dynamics of near-threshold excited states of the isolated chloranil radical anion are investigated using photoelectron imaging. The photoelectron images taken at 480 nm clearly indicate resonance-enhanced photodetachment via a bound electronic excited state. Time-resolved photoelectron imaging reveals that the excited state rapidly decays on a timescale of 130 fs via internal conversion. The ultrafast relaxation dynamics of excited states near threshold are pertinent to common electron acceptor molecules based on the quinone moiety and may serve as doorway states that enable efficient electron transfer in the highly exergonic inverted regime, despite the presence of large free energy barriers.
2010
1.
Roberts G M, Lecointre J, Horke D A, Verlet J R R
Spectroscopy and Dynamics of the 7,7,8,8-Tetracyanoquinodimethane Radical Anion. Journal Article
In: Phys. Chem. Chem. Phys., vol. 12, no. 23, pp. 6226–6232, 2010.
Abstract | Links | BibTeX | Altmetric | Tags: Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging
@article{Roberts:Phys.Chem.Chem.Phys.12:6226,
title = {Spectroscopy and Dynamics of the 7,7,8,8-Tetracyanoquinodimethane Radical Anion.},
author = {Gareth M Roberts and Julien Lecointre and Daniel A Horke and Jan R R Verlet},
url = {http://dx.doi.org/10.1039/c001438a},
doi = {10.1039/c001438a},
year = {2010},
date = {2010-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {12},
number = {23},
pages = {6226--6232},
abstract = {The photoelectron spectrum of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion has been measured at 3.1 eV. Additionally, the ultrafast relaxation dynamics of the first excited state (1(2)B(3u)) of TCNQ(-) have been studied using time-resolved photoelectron spectroscopy, which reveals that it undergoes internal conversion back to the ground state ((2)B(2g)) with an associated lifetime of 650 fs and shows evidence of coherent nuclear motion. From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. - Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. - Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. - Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. - Roberts, Gareth M; Lecointre, Julien; Horke, Daniel A; Verlet, Jan R R )},
keywords = {Anion spectroscopy, dynamics, Non-adiabatic dynamics, photoelectron imaging, Photoelectron spectroscopy, velocity-map imaging},
pubstate = {published},
tppubtype = {article}
}
The photoelectron spectrum of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion has been measured at 3.1 eV. Additionally, the ultrafast relaxation dynamics of the first excited state (1(2)B(3u)) of TCNQ(-) have been studied using time-resolved photoelectron spectroscopy, which reveals that it undergoes internal conversion back to the ground state ((2)B(2g)) with an associated lifetime of 650 fs and shows evidence of coherent nuclear motion. From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. – Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. – Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. – Roberts, Gareth M; Lecointre, Julien; Horke, Daniel a; Verlet, Jan R R ) From Duplicate 1 ( Spectroscopy and dynamics of the 7,7,8,8-tetracyanoquinodimethane radical anion. – Roberts, Gareth M; Lecointre, Julien; Horke, Daniel A; Verlet, Jan R R )