Resonance Raman activity in odd quanta of the trans bending vibration of acetylene: Strong vibronic coupling in the X̃ to à and X̃ to B̃ transitions
✍ Scribed by Jerome Berryhill; Shekhar Pramanick; Marek Z. Zgierski; Francesco Zerbetto; Bruce S. Hudson
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 588 KB
- Volume
- 205
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Resonance Raman spectra of acetylene with excitation at 204 and 178 nm in the region of the 2-A ( ICI-' 'Z; in Dmh) and x+& '2: --t 'Au in Dmh) transitions exhibit very strong activity in both even and odd quanta of the $( v,) trans bending vibration. Enhancement of the two-quantum even overtone is expected from linear vibronic activity in these forbidden transitions resulting in quadratic (C-term) Raman activity. The higher even quanta overtone activity is consistent with strongly bent excited states or nonlinear vibronic coupling. The induction of intensity in the odd overtones of this non-totally symmetric vibrational mode, however, requires mixed linear and auadratic vibronic coupling involving two different allowed excitations (to states of 'II, and 'Z$ symmetry).