Journal
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
Volume 53, Issue 22, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1361-6455/abb1fd
Keywords
photochemistry; time-resolved dynamics; ultrafast processes; free-electron laser science; velocity map imaging; photodissociation; charge transfer
Categories
Funding
- EU [730872]
- Max Planck Society
- BMBF [05K10KT2, 05K13KT2, 05K16KT3, 05K10KTB, FSP-302]
- UK EPSRC [M Bu-EP/S028617/1, CV-EP/L005913/1]
- Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy [DE-FG02-86ER13491, DE-SC0019451]
- Helmholtz Initiative and Networking Fund through the Young Investigator Groups Program
- Swedish Research Council
- Swedish Foundation for Strategic Research
- National Science Foundation
- EPSRC [EP/L005913/1, EP/T021675/1, EP/S028617/1] Funding Source: UKRI
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The predissociation dynamics of the 6s ((BE)-E-2) Rydberg state of gas-phase CH3I were investigated by time-resolved Coulomb-explosion imaging using extreme ultraviolet (XUV) free-electron laser pulses. Inner-shell ionization at the iodine 4d edge was utilized to provide a site-specific probe of the ensuing dynamics. The combination of a velocity-map imaging (VMI) spectrometer coupled with the pixel imaging mass spectrometry (PImMS) camera permitted three-dimensional ionic fragment momenta to be recorded simultaneously for a wide range of iodine charge states. In accord with previous studies, initial excitation at 201.2 nm results in internal conversion and subsequent dissociation on the lower-lying A-state surface on a picosecond time scale. Examination of the time-dependent yield of low kinetic energy iodine fragments yields mechanistic insights into the predissociation and subsequent charge transfer following multiple ionization of the iodine products. The effect of charge transfer was observed through differing delay-dependencies of the various iodine charge states, from which critical internuclear distances for charge transfer could be inferred and compared to a classical over-the-barrier model. Time-dependent photofragment angular anisotropy parameters were extracted from the central slice of the Newton sphere, without Abel inversion, and highlight the effect of rotation of the parent molecule before dissociation, as observed in previous works. Our results demonstrate the ability to perform three-dimensional ion imaging at high event rates and showcase the potential benefits of this approach, particularly in relation to further time-resolved studies at free-electron laser facilities.
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