/sup 2/Pireverse arrowX /sup 2/. sigma. /sup +/ infrared electronic transition of C/sub 2/H

Journal Article · Tue Mar 15 04:00:00 EST 1983 · J. Chem. Phys.; (United States)

OSTI ID:5503024

Carrick, P G; Merer, A J; Curl, Jr, R F

Five bands of the A /sup 2/Pireverse arrowX /sup 2/..sigma../sup +/ lowest electronic transition of C/sub 2/H have been observed in the region 3600--4200 cm/sup -1/ in an argon discharge over polyacetylene using color center laser spectroscopy with magnetic rotation sensitivity enhancement. The band origins are approximately 3692, 3773, 3785, 4011, and 4106 cm/sup -1/. Rotational assignments and preliminary fittings of all five bands have been made. Four of the bands have a /sup 2/..sigma../sup +/ lower vibronic state which is undoubtedly the ground vibronic state of the molecule, and different /sup 2/Pi upper vibronic states which correspond to mixtures of the lowest vibronic state of the A electronic state and three different vibrationally excited levels of the X electronic state with an odd number of quanta in the bending mode and overall /sup 2/Pi symmetry. These three ground state vibrational levels have been tentatively assigned as (1,1,0), (0,1,2), and (0,5,1). The four /sup 2/Pi vibronic levels are mixed by vibronic coupling between the X and A electronic states thereby providing electronic oscillator strength for the vibrational transitions. The fifth band is a /sup 2/..sigma../sup -/reverse arrow/sup 2/Pi hot band with the lower state the first excited bending level (0,1,0) of the ground electronic state and upper state the /sup 2/..sigma../sup -/ component of the (0,1,0) excited bending level of the excited electronic state. From these observations a value of 1.30 A for the CC bond length in the excited electronic state and a value of approx.375 cm/sup -1/ for the bending frequency of the X ground electronic state are obtained.

• Research Organization: Chemistry Department and the Rice Quantum Institute, Rice University, Houston, Texas 77251
• OSTI ID: 5503024
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 78:6; ISSN JCPSA
• Country of Publication: United States
• Language: English

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74 ATOMIC AND MOLECULAR PHYSICS
ACETYLENE
ALKYNES
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HYDROCARBONS
INFRARED SPECTRA
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OSCILLATOR STRENGTHS
POLYACETALS
POLYMERS
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