VIBRATION-ROTATION SPECTRA OF C-13-CONTAINING ACETYLENE - THE NU(1)/NU(2)+2-NU(5) FERMI DYAD

High-resolution vibration-rotation spectra of (C2H2)-C-13 have been recorded in the wavenumber regions 1100-1240, 1730-1810, 2550-2700, and 3130-3280 cm-1 at Doppler- or pressure-limited resolution. In these spectral ranges bands involving the nu1 and nu2 stretchings and the bending-stretching combination levels with nu2 = 1, nu4 = 1, nu5 less-than-or-equal-to 2 have been analyzed. The main purpose of the analysis was the treatment of the Fermi resonance occurring between the nu1(SIGMA(G)+) and the nu2 + 2nu5(SIGMA(g)+) levels, detected as nu1 <-- nu5 and nu2 + 2nu5 <-- nu5 hot bands in the 4-mum region. The global analysis of all the observed transitions provided a set of 20 molecular parameters which fully characterize the stretching and bending-stretching combination states. The vibrational coupling terms which describe the Fermi resonance are also computed with high accuracy. (C) 1994 Academic Press. Inc.