Centrifugal Distortion Analysis and Pressure Broadening Studies for l-Type Doublet Transitions of Cyanoacetylene-15N in the Microwave Range

Abstract

With the help of Fourier transform spectrometers in the range from 8 GHz to 26.5 GHz. l-type doublet transitions of HCCC15N in the first excited state of the degenerate bending vibration ν7, with 36 ≤ J ≤ 65, have been investigated. The l-dependence of the resonance frequencies was analy­sed to yield the doubling constant q(0) together with the correction terms q(1) and q(2) due to first and second order contributions from centrifugal distortion. For the lines in X- and Ku-band (8 GHz to 18 GHz) the self-broadening linewidth parameters Γp were determined from the pressure dependence of coherence decay rates 1/T2 of the observed transient emission signals, following pulsed microwave excitation. For the lines with J = 36 and 41, foreign gas broadening in mixtures of HCCC15N with H,. D, and He has also been studied. The experimental results are compared with theoretical predictions, based on a perturbative treatment of binary collisions.