N 2-broadening coefficients in the ν2 and ν4 bands of PH 3

Abstract

N 2-broadening coefficients are measured for 61 transitions of PH 3 in the Q R branch of the ν 2 band and the P P, R P, S P, and P Q branches of the ν 4 band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 16 and K from 0 to 11 are located between 1008 and 1106 cm −1. The collisional widths are determined by fitting each spectral line with a Voigt profile, a Rautian profile, and a speed-dependent Rautian profile. The latter models provide larger broadening coefficients than the Voigt model. These coefficients have also been calculated on the basis of a semiclassical model of interacting linear molecules by considering an atom–atom Lennard-Jones potential in addition to the electrostatic contributions. The theoretical results are in good agreement with the experimental data and reproduce the J dependence of the broadenings, but their decrease at high J values is overestimated for the Q R ( J, K) transitions.