Projects per year
Abstract
The photodissociation dynamics of ethyl bromide and ethyl iodide cations (C2H5Br+ and C2H5I+) have been studied. Ethyl halide cations were formed through vacuum ultraviolet (VUV) photoionization of the respective neutral parent molecules at 118.2 nm, and were photolysed at a number of ultraviolet (UV) photolysis wavelengths, including 355 nm and wavelengths in the range from 236 to 266 nm. Time-offlight mass spectra and velocity-map images have been acquired for all fragment ions and for ground (Br) and spin-orbit excited (Br*) bromine atom products, allowing multiple fragmentation pathways to be investigated. The experimental studies are complemented by spin-orbit resolved ab initio calculations of cuts through the potential energy surfaces (along the RC-Br/I stretch coordinate) for the ground and first few excited states of the respective cations. Analysis of the velocity-map images indicates that photoexcited C2H5Br+ cations undergo prompt C-Br bond fission to form predominantly C2H5+ + Br* products with a near-limiting ` parallel' recoil velocity distribution. The observed C2H3+ + H-2 + Br product channel is thought to arise via unimolecular decay of highly internally excited C2H5+ products formed following radiationless transfer from the initial excited state populated by photon absorption. Broadly similar behaviour is observed in the case of C2H5I+, along with an additional energetically accessible C-I bond fission channel to form C2H5 + I+ products. HX (X = Br, I) elimination from the highly internally excited C2H5X+ cation is deemed the most probable route to forming the C2H4 (+) fragment ions observed from both cations. Finally, both ethyl halide cations also show evidence of a minor C-C bond fission process to form CH2X+ + CH3 products.
Original language | English |
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Pages (from-to) | 2167-2178 |
Number of pages | 12 |
Journal | Physical Chemistry Chemical Physics |
Volume | 16 |
Issue number | 5 |
Early online date | 26 Nov 2013 |
DOIs | |
Publication status | Published - 2014 |
Keywords
- PHOTOELECTRON-PHOTOION COINCIDENCE
- ENERGY RELEASE DISTRIBUTIONS
- PHOTODISSOCIATION DYNAMICS
- KINETIC-ENERGY
- METHYL-IODIDE
- THERMOCHEMICAL PROPERTIES
- MULTIPHOTON IONIZATION
- ELECTRONIC EXCITATION
- OSCILLATOR-STRENGTH
- LOSS SPECTROSCOPY
Projects
- 1 Finished
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NEW HORIZONS IN CHEMICAL AND PHOTOCHEMICAL DYNAMICS
Orr-Ewing, A. J. & Ashfold, M. N. R.
1/10/08 → 1/04/14
Project: Research