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Issue 41, 2011
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Time-resolved predissociation of the vibrationless level of the B state of CH3I

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Abstract

The predissociation dynamics of the vibrationless level of the first Rydberg 6s (B 1E) state of CH3I has been studied by femtosecond-resolved velocity map imaging of both the CH3 and I photofragments. The kinetic energy distributions of the two fragments have been recorded as a function of the pump–probe delay, and as a function of excitation within the umbrella and stretching vibrational modes of the CH3 fragment. These observations are made by using (2 + 1) Resonant Enhanced MultiPhoton Ionization (REMPI) via the Image ID:c1cp22057h-t1.gif state of CH3 to detect specific vibrational levels of CH3. The vibrational branching fractions of the CH3 are recovered by using the individual vibrationally state-selected CH3 distributions to fit the kinetic energy distribution obtained by using nonresonant multiphoton ionization of either the I or the CH3 fragment. The angular distributions and rise times of the two fragments differ significantly. These observations can be rationalized through a consideration of the alignment of the CH3 fragment and the effect of this alignment on its detection efficiency. Two additional dissociation channels are detected: one associated with Rydberg states near 9.2 eV that were observed previously in photoelectron studies, and one associated with photodissociation of the parent cation around 15 eV.

Graphical abstract: Time-resolved predissociation of the vibrationless level of the B state of CH3I

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Article information


Submitted
23 Jun 2011
Accepted
31 Aug 2011
First published
22 Sep 2011

Phys. Chem. Chem. Phys., 2011,13, 18485-18496
Article type
Paper

Time-resolved predissociation of the vibrationless level of the B state of CH3I

N. Thiré, R. Cireasa, D. Staedter, V. Blanchet and S. T. Pratt, Phys. Chem. Chem. Phys., 2011, 13, 18485
DOI: 10.1039/C1CP22057H

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