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

Abstract

N 2-broadening coefficients have been measured for 41 transitions of PH 3 at −100 °C in the Q R branch of the ν 2 band and the P P, R P, and S P branches of the ν 4 band, using a tunable diode-laser spectrometer. The recorded lines with J values ranging from 1 to 13 and K from 0 to 10 are located between 1026 and 1093 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. By comparing broadening coefficients at room and low temperatures, the temperature dependence of these broadenings has been determined both experimentally and theoretically.