Vibration-Rotation Spectra of 13C-Containing Acetylene: The Stretching Fundamentals

High-resolution vibration-rotation spectra of the stretching fundamentals of 13C2H2and 12C13CH2have been recorded at Doppler- or pressure-limited resolution in the 8-, 4-, and 3-μm spectral regions. Both cold and hot bands involving stretching and stretching-bending combination levels have been analyzed. The complete treatment of the weak quartic anharmonic resonance between the levels ν3and ν2+ ν4+ ν5(Σ+u) in 13C2H2has been performed, yielding the effective anharmonic constant K2345and the unperturbed value of the ν3fundamental for this isotopomer. The analysis of the bands of the 12C13CH2isotopomer provides values for vibrational energies and rotational constants of the first excited states of all stretching vibrations, including the ν2= 1 level, not detected before in IR spectra.