Acetylene at the threshold of isomerization

Journal Article · Thu Apr 13 04:00:00 EDT 2000 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp992428u· OSTI ID:20034402

Jacobson, M P; Field, R W

This article reviews recent research on acetylene which is intended as a contribution to the understanding of intramolecular vibrational energy flow when it is poorly described by either statistical (i.e., RRKM) or purely separable (i.e., harmonic oscillator/normal mode) models. The experimental spectra that inform this investigation are {approximately}7 cm{sup {minus}1} resolution dispersed fluorescence spectra of the acetylene S{sub 1} {r_arrow} S{sub 0} system. Above 10,000 cm{sup {minus}1} of vibrational energy, these spectra are extremely congested and cannot be analyzed using conventional spectroscopic assignment procedures. Instead, a numerical pattern recognition procedure is utilized to disentangle spectroscopic patterns that are associated with approximately conserved polyad quantum numbers. This pattern recognition analysis makes possible detailed modeling of the short-time ({approximately}1 ps) but large-amplitude vibrational dynamics of acetylene at high energy (15,000 cm{sup {minus}1}), which is demonstrated here to be dominated by regularity even for the low-frequency bending motions (22 quanta of bend excitation). That is, a few stable motions dominate the large-amplitude bending dynamics, including local bend (one hydrogen bending), which is closely related to the acetylene-vinylidene isomerization coordinate, and a new type of vibrational motion that the authors call counter-rotation, in which the two hydrogens undergo circular motions on opposite ends of the CC core.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (US)
• Sponsoring Organization: US Department of the Air Force; US Department of Energy; US Department of the Army
• DOE Contract Number: FG02-87ER13671
• OSTI ID: 20034402
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 14 Vol. 104; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACETYLENE
ISOMERIZATION
REVIEWS
SPECTRA
VIBRATIONAL STATES