Anomalously slow intramolecular vibrational redistribution in the acetylene {tilde X}thinsp{sup 1}{Sigma}{sub g}{sup +} state above 10thinsp000 cm{sup {minus}1} of internal energy

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476983· OSTI ID:641510

Jacobson, M P; OBrien, J P; Field, R W ^[1]

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1. Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

We have identified, in dispersed fluorescence spectra of acetylene {tilde A}thinsp{sup 1}A{sub u}{r_arrow}{tilde X}thinsp{sup 1}{Sigma}{sub g}{sup +} emission, a series of bright states between 10thinsp000 and 15thinsp000 cm{sup {minus}1} of internal energy which display anomalously slow intramolecular vibrational redistribution. That is, these bright states display virtually no fractionation at internal energies at which the majority of other observed bright states are fractionated over several hundred cm{sup {minus}1} in a complicated fashion. The anomalous bright states are distinguished from the other nearly isoenergetic bright states only by the way in which the vibrational excitation is distributed among the CC stretch and {ital trans} bend modes; specifically, the anomalous bright states have relatively low excitation in the {ital trans} bend mode (v{sub 4}{le}8), with the remainder of the vibrational excitation in the CC stretch mode (v{sub 2}{le}6). A refinement of the acetylene global effective Hamiltonian permits detailed insight into the mechanism of the anomalously slow intramolecular vibrational redistribution, and reveals that the relatively simple fractionation patterns of these bright states can be adequately described in terms of a system of 4 interacting zero-order states which are coupled by Darling-Dennison bending resonances, vibrational l-resonance, and an anharmonic {open_quotes}3,245{close_quotes} resonance. The refined effective Hamiltonian also permits the assignment of similar, minimally perturbed bright states up to at least 17thinsp500 cm{sup {minus}1} of internal energy. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 641510
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 109; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ACETYLENE
ELECTRONIC STRUCTURE
EMISSION SPECTRA
ENERGY TRANSFER
FLUORESCENCE
VIBRATIONAL STATES