1. Internal state distributions of fragment HCO via S[sub 0] and T[sub 1] pathways of glyoxal after photolysis in the ultraviolet region.
- Author
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Chih Chieh Kao, Richard N., Mei-Lin Ho, Richard N., Ming-Wei Chen, Richard N., Sheng-Jui Lee, Richard N., and I-Chia Chen
- Subjects
PHOTODISSOCIATION ,PHOTOCHEMISTRY ,GLYOXALASE ,ORGANIC compounds ,FRAGMENTATION reactions ,CHEMICAL reactions ,NUCLEAR excitation ,ENERGY levels (Quantum mechanics) - Abstract
The dynamics of photodissociation of glyoxal (HOC–COH) near the dissociation threshold on the triplet manifold are studied through measurement of distributions of nascent fragment HCO in various internal states. Three rotational levels 1[sub 01][sup *], 4[sub 13][sup *], and 3[sub 21][sup *]+3[sub 22][sup *] of vibrational state U (excitation wavelength ∼394.4 nm, origin at 25 331.865 cm-1) of glyoxal in state à [sup 1]A[sub u] and two other vibrational states at excitation wavelengths 390.33 and 382.65 nm are selected to produce fragment HCO. By means of fluorescence in the transition B [sup 2]A[sup ′]–X [sup 2]A[sup ′] of HCO, we determined the relative populations of internal states of that fragment. Rotational states of product HCO up to N=26 and K=2 are populated, and bimodal distributions of these rotational states are observed for the photolysis wavelengths used in this work. The high rotational part of the distribution with average energy near values calculated on the basis of the statistical model—phase-space theory is assigned to arise from glyoxal on its S[sub 0] surface, and the low rotational part from the T[sub 1] surface with an exit barrier. After photolysis near the threshold region on the triplet surface, HCO arising from the T[sub 1] state appears to be a major component of products because these rotational levels 1[sub 01][sup *], 4[sub 13][sup *], and 3[sub 2][sup *] of U state selected are gateway states with an enhanced rate of intersystem crossing. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]
- Published
- 2004
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