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Photodissociation dynamics of methyl iodide across the A-band probed by femtosecond extreme ultraviolet photoelectron spectroscopy

Photodissociation dynamics of methyl iodide across the A-band probed by femtosecond extreme ultraviolet photoelectron spectroscopy
Photodissociation dynamics of methyl iodide across the A-band probed by femtosecond extreme ultraviolet photoelectron spectroscopy

The dissociation dynamics of CH3I at three UV pump wavelengths (279 nm, 254 nm, 243 nm) are measured using an extreme ultraviolet probe in a time-resolved photoelectron spectroscopy experiment. The results are compared with previously published data at a pump wavelength of 269 nm, [2020, Phys. Chem. Chem. Phys., 22, 25695], with complementary photoelectron spectroscopy experiments performed using a multiphoton ionization (MPI) probe [2019, Phys. Chem. Chem. Phys., 21, 11142] and with the recent action spectroscopy measurements of Murillo-Sánchez et al [2020, J. Chem. Phys., 152, 014304]. The measurements at 279 nm and 243 nm show signals that are consistent with rapid dissociation along the C-I bond occurring on timescales that are consistent with previous measurements. The measurements at 254 nm show a significantly longer excited state lifetime with a secondary feature appearing after 100 fs which is indicative of more complex dynamics in the excited state. The time-dependence of the changes are consistent with the previously measured MPI photoelectron spectroscopy measurements of Warne et al, [2019, Phys. Chem. Chem. Phys., 21, 11142]. The consistency of the signal appearance across ionization processes suggests that the extended observation time at 254 nm is not an artefact of the previously used MPI process but is caused by more complex dynamics on the excited state potential.Whether this is caused by complex vibrational dynamics on the dominant 3Q0 state or is due to enhanced population and dynamics on the 1Q1 state remains an open question.

Chemical dynamics, Photodissociation, Photoelectron spectroscopy
0953-4075
Minns, Russell
85280db4-c5a6-4a4c-82fe-75693c6a6045
Downes-Ward, Briony, Ruth
fa385501-e59a-4f84-b996-9bd924afe846
Warne, Emily
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Woodhouse, Joanne
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Parkes, Michael
69a61bd6-eb1a-4671-8ed3-78a7d5fbe6b1
Springate, Emma
671791ff-7c71-461c-84b3-7d882dff8048
Pearcy, Philip
67036cfb-96c6-4183-9119-9de4ab47afc5
Zhang, Yu
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Karras, Gabriel
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Wyatt, Adam
d1539cce-7dfd-4b3d-8e97-22df1e0a5615
Chapman, Richard
cec30dba-8ae2-4e97-8dc7-73a2155a97ea
Minns, Russell
85280db4-c5a6-4a4c-82fe-75693c6a6045
Downes-Ward, Briony, Ruth
fa385501-e59a-4f84-b996-9bd924afe846
Warne, Emily
63799bdf-67fa-4dd8-adac-b963a9587a28
Woodhouse, Joanne
94d6c235-3e1e-44bc-8379-525862fd382c
Parkes, Michael
69a61bd6-eb1a-4671-8ed3-78a7d5fbe6b1
Springate, Emma
671791ff-7c71-461c-84b3-7d882dff8048
Pearcy, Philip
67036cfb-96c6-4183-9119-9de4ab47afc5
Zhang, Yu
46bd3a4e-2bad-478c-979e-02e645b8e0a9
Karras, Gabriel
5087628a-4a33-4bb2-99ce-e6d5a577da42
Wyatt, Adam
d1539cce-7dfd-4b3d-8e97-22df1e0a5615
Chapman, Richard
cec30dba-8ae2-4e97-8dc7-73a2155a97ea

Minns, Russell, Downes-Ward, Briony, Ruth, Warne, Emily, Woodhouse, Joanne, Parkes, Michael, Springate, Emma, Pearcy, Philip, Zhang, Yu, Karras, Gabriel, Wyatt, Adam and Chapman, Richard (2021) Photodissociation dynamics of methyl iodide across the A-band probed by femtosecond extreme ultraviolet photoelectron spectroscopy. Journal of Physics B: Atomic and Molecular Physics, 54 (13), [134003]. (doi:10.1088/1361-6455/ac08f3).

Record type: Article

Abstract

The dissociation dynamics of CH3I at three UV pump wavelengths (279 nm, 254 nm, 243 nm) are measured using an extreme ultraviolet probe in a time-resolved photoelectron spectroscopy experiment. The results are compared with previously published data at a pump wavelength of 269 nm, [2020, Phys. Chem. Chem. Phys., 22, 25695], with complementary photoelectron spectroscopy experiments performed using a multiphoton ionization (MPI) probe [2019, Phys. Chem. Chem. Phys., 21, 11142] and with the recent action spectroscopy measurements of Murillo-Sánchez et al [2020, J. Chem. Phys., 152, 014304]. The measurements at 279 nm and 243 nm show signals that are consistent with rapid dissociation along the C-I bond occurring on timescales that are consistent with previous measurements. The measurements at 254 nm show a significantly longer excited state lifetime with a secondary feature appearing after 100 fs which is indicative of more complex dynamics in the excited state. The time-dependence of the changes are consistent with the previously measured MPI photoelectron spectroscopy measurements of Warne et al, [2019, Phys. Chem. Chem. Phys., 21, 11142]. The consistency of the signal appearance across ionization processes suggests that the extended observation time at 254 nm is not an artefact of the previously used MPI process but is caused by more complex dynamics on the excited state potential.Whether this is caused by complex vibrational dynamics on the dominant 3Q0 state or is due to enhanced population and dynamics on the 1Q1 state remains an open question.

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e-pub ahead of print date: 7 June 2021
Published date: July 2021
Additional Information: Funding Information: RSM thanks the Royal Society for a University Research Fellowship (UF100047, UF150655). RSM and JW thank the EPSRC for funding (EP/R010609/1).BDWthanks the Central Laser Facility and Chemistry at the University of Southampton for a studentship. EMWthanks Chemistry at the University of Southampton for a studentship. Access to Artemis at the Central Laser Facility was provided by the STFC. We thank John Dyke for very useful conversations and Phil Rice for technical assistance.
Keywords: Chemical dynamics, Photodissociation, Photoelectron spectroscopy

Identifiers

Local EPrints ID: 449795
URI: http://eprints.soton.ac.uk/id/eprint/449795
ISSN: 0953-4075
PURE UUID: 9c9f6c03-c8da-4b1a-b98c-f405ba4f8b18
ORCID for Russell Minns: ORCID iD orcid.org/0000-0001-6775-2977
ORCID for Joanne Woodhouse: ORCID iD orcid.org/0000-0002-0771-5362

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Date deposited: 17 Jun 2021 16:34
Last modified: 17 Mar 2024 03:54

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Contributors

Author: Russell Minns ORCID iD
Author: Briony, Ruth Downes-Ward
Author: Emily Warne
Author: Joanne Woodhouse ORCID iD
Author: Michael Parkes
Author: Emma Springate
Author: Philip Pearcy
Author: Yu Zhang
Author: Gabriel Karras
Author: Adam Wyatt
Author: Richard Chapman

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