Toulson, B.W., Alaniz, J.P., Hill, J.G. et al. (1 more author) (2016) Near-UV photodissociation dynamics of CH2I2. Physical Chemistry Chemical Physics, 18. pp. 11091-11103. ISSN 1463-9076
Abstract
The near-UV photodissociation dynamics of CH2I2 has been investigated using a combination of velocitymap (slice) ion imaging and ab initio calculations characterizing the excited states. Ground state I(2 P3/2) and spin-orbit excited I*(2 P1/2) atoms were probed using 2+1 resonance-enhanced multiphoton ionization (REMPI) or with single-photon VUV ionization. Two-color ion images were recorded at pump wavelengths of 355 nm, 266 nm and 248 nm, and one-color ion images at the REMPI wavelengths of ~304 nm and ~280 nm. Analysis of the ion images shows that, regardless of iodine spin-orbit state, ~20% of the available energy is partitioned into translation ET at all excitation wavelengths indicating that the CH2I co-fragment is formed highly internally excited. The translational energy distributions comprise a slow, “statistical” component that peaks near zero and faster components that peak away from zero. The slow component makes an increasingly large contribution to the distribution as the excitation wavelength is decreased. The C–I bond dissociation energy of D0 = 2.155±0.008 eV is obtained from the trend in the ET release of the faster components with increasing excitation energy. The I and I* ion images are anisotropic, indicating prompt dissociation, and are characterized by β parameters that become increasingly positive with increasing ET. The decrease in β at lower translational energies can be attributed to deviation from axial recoil. MRCI calculations including spin-orbit coupling have been performed to identify the overlapping features in the absorption spectrum and characterize onedimensional cuts through the electronically excited potential energy surfaces. The excited states are of significantly mixed singlet and triplet character. At longer wavelengths, excitation directly accesses repulsive states primarily of B1 symmetry, consistent with the observed !β∀, while shorter wavelengths accesses bound states, also of B1 symmetry that are crossed by repulsive states.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Royal Society of Chemistry 2016. This is an author produced version of a paper subsequently published in Physical Chemistry Chemical Physics. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 29 Mar 2016 11:58 |
Last Modified: | 18 Jul 2017 17:19 |
Published Version: | http://dx.doi.org/10.1039/C6CP01063F |
Status: | Published |
Publisher: | Royal Society of Chemistry |
Refereed: | Yes |
Identification Number: | 10.1039/C6CP01063F |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:97214 |