High resolution spectroscopic detection of acetylene--vinylidene isomerization by spectral cross correlation

Journal Article · Sun Oct 01 04:00:00 EDT 1989 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.456828· OSTI ID:5649701

Chen, Y; Jonas, D M; Kinsey, J L; 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 (US)

Information about the unimolecular acetylene (HC 3/4 CH){leftrightarrow}vinylidene (H{sub 2}C=C:) isomerization on the {ital S}{sub 0} energy surface has been extracted from vibrationally unassigned high resolution stimulated emission pumping (SEP) spectra of acetylene. The combination of a new pattern recognition scheme, spectral cross correlation (SCC) with complete nuclear permutation-inversion (CNPI) group theory is shown to be a powerful new technique for characterizing bond rearrangement in highly vibrationally excited normally rigid polyatomic molecules. SCC detects isomerization resonances'' which destroy an approximate vibrational symmetry (e.g., the number of {ital cis}-bending quanta). The energies (relative to the zero point level of the stablest isomer) and widths of such resonances provide information about the energies'' of isomer rovibrational levels and the isomer-level-specific isomerization rate. Vinylidene isomerization resonances may be distinguished from ordinary acetylene Fermi or Coriolis perturbations by a unique rotational symmetry dependence due to the correlation between acetylene ({ital D}{sub {infinity}{ital h}}(M)) and vinylidene ({ital C}{sub 2{ital v}}(M)) levels in the CNPI group G{sub 8}. An SCC map of the HCCH {ital S}{sub 0} 15 000--15 900 cm{sup {minus}1} energy region above the zero point level was obtained by comparing SEP spectra recorded via {ital S}{sub 1}({ital {tilde A}} {sup 1}{ital A}{sub {ital u}})3{sup 3} and 2{sup 1}6{sup 2} {ital K}{sub {ital a}}=1 intermediate levels. The predicted rotational symmetry dependence of the SCC was found between 15 410--15 640 cm{sup {minus}1}, but the vinylidene resonance line shape was obscured by Franck--Condon interference effects from well known perturbations between the 3{sup 3} and 2{sup 1}6{sup 2} SEP intermediate levels.

• OSTI ID: 5649701
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 91:7; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
ACETYLENE
ALKYNES
CARBENES
CHEMICAL REACTIONS
ENERGY LEVELS
EXCITED STATES
HYDROCARBONS
ISOMERIZATION
OPTICAL PUMPING
ORGANIC COMPOUNDS
PUMPING
RADICALS
RESOLUTION
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
VIBRATIONAL STATES