INVESTIGATION OF THE NU-5 BAND OF METHYLACETYLENE BY INFRARED-LASER STARK AND MICROWAVE SPECTROSCOPY

Microwave spectra have been studied in the ground and ν5 = 1 (C-C stretching mode) states of methylacetylene. From these data, dipole moments and rotational and centrifugal distortion constants have been determined, as follows: μD(0) = 0.7839 ± 0.0010 D, μD(5) = 0.7954 ± 0.0010 D, B5 = 8508.119 ± 0.003 MHz, DJ(5) = 1.8 ± 0.2 kHz, and DJK(5) = 169 ± 1 kHz. Laser Stark spectra have been obtained for the ν5 band of this molecule and from these spectra the following vibration-rotation parameters have been determined: ν50 = 93.27540 ± 0.00007 cm-1, A 5 - A0 = -227.0 ± 2.3 MHz and DK(5) - DK(0) = -0.05 ± 0.50 MHz. The higher-J and -K states of the ν5 = 1 state appear to be perturbed. Copyright © 1980 by Academic Press, Inc.