Ar-induced pressure effects in the nu(1)+3 nu(3) absorption band in (C2H2)-C-12

We have used a Ti:sapphire autoscan laser spectrometer to measure Ar-induce d pressure-broadening, narrowing and shift effects for 24 individual vibrat ion-rotation lines in the nu(1) + 3 nu(3) band of (C2H2)-C-12. The acetylen e and total pressures ranged between 10 and 20 Torr, and between 30 and 310 Torr, respectively. The Voigt profile accounted for the higher pressure me asurements while the soft and hard collision profiles were required to fit the lower pressure measurements. Lineshift parameters that are significantl y different from the overall behaviour in the band were observed for the R( 17) and P(19) lines and are qualitatively attributed to the influence of an intramolecular Coriolis-type: coupling on the interparticle interaction po tential. Those results confirm all trends of self-collisional measurements recently reported for this band. (C) 2000 Elsevier Science B.V. All rights reserved.