Journal of Chemical Physics, Vol.111, No.17, 7954-7960, 1999
Laser spectroscopy of the nu(1)+3 nu(3) absorption band in (C2H2)-C-12. I. Pressure broadening and absolute line intensity measurements
We have developed a Ti:Sa autoscan laser spectrometer and used it to perform a detailed investigation of individual line profiles in the nu(1)+3 nu(3) band of (C2H2)-C-12. Pressure self-broadening effects were measured for most lines with J " values ranging from 0 to 22, and for pressures between 10 and 600 Torr. The high-pressure data points (p > 250 Torr) are fitted satisfactorily by a Voigt profile. Line narrowing, characterized by an underestimation of the Lorentz contribution to the Voigt profile, was observed for the low pressures range (p < 150 Torr), indicating the influence of molecular confinement. The two usual limit models (soft and hard collisions) were fitted to the observed line shapes in order to extract more precise information concerning the pressure broadening. The present results confirm the absence of strong vibrational dependence in the self-broadening coefficients. Absolute line intensities are also determined in the fitting procedure. No significant differences were found for the two pressure domains if the appropriate model in each range is used.