Pure bending dynamics in the acetylene {tilde X}thinsp{sup 1}{Sigma}{sub g}{sup +} state up to 15thinsp000 cm{sup {minus}1} of internal energy

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476529· OSTI ID:636141

Jacobson, M P; OBrien, J P; Silbey, R J; 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 investigate the large-amplitude bending dynamics of acetylene, in its ground electronic state, using an effective Hamiltonian model that reproduces all relevant experimental data, up to 15thinsp000 cm{sup {minus}1} in internal energy, with 1.4 cm{sup {minus}1} accuracy (1{sigma}). The experimental data which make this analysis possible are derived from the dispersed fluorescence (DF) data set that we recently reported [J. P. O{close_quote}Brien {ital et al.}, J. Chem. Phys. {bold 108}, 7100 (1998)] for the acetylene {tilde A}thinsp{sup 1}A{sub u}{r_arrow}{tilde X}thinsp{sup 1}{Sigma}{sub g}{sup +} system, which includes DF spectra recorded from five different vibrational levels of the {tilde A}thinsp{sup 1}A{sub u} state. A numerical pattern recognition technique has permitted the assignment of polyad quantum numbers to observed transitions in these spectra, with up to 15thinsp000 cm{sup {minus}1} in internal energy. Here we analyze a special subset of the identified polyads, those which involve excitation exclusively in the {ital trans} and {ital cis} bending modes: the pure bending polyads. The bending dynamics that is encoded in these polyads is analyzed using both frequency and time-domain formalisms. Among the conclusions of this analysis is that, in many ways, the observed bending dynamics is somewhat simpler at 15thinsp000 than it is at 10thinsp000 cm{sup {minus}1}; this rather surprising result is explained in terms of qualitative changes in the structures of the pure bending polyads as a function of increasing internal energy. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 636141
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 109; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ACETYLENE
ELECTRONIC STRUCTURE
FLUORESCENCE
GROUND STATES
ORGANIC COMPOUNDS
PATTERN RECOGNITION
VIBRATIONAL STATES