Detailed profile analysis of millimetre 502 and 602 GHz N₂O–N₂(O₂) lines at room temperature for collisional linewidth determination

Abstract

Deviations of experimental millimetre-absorption line shapes from the usual Voigt profile are evidenced for two room-temperature rotational transitions J ¼ 20 19 (502 GHz) and J ¼ 24 23 (602 GHz) of nitrous oxide perturbed by nitrogen and oxygen. These deviations are shown to be due to collisional narrowing processes encompassed by more sophisticated speed-dependent Voigt or Galatry models. The deduced collision-regime line broadening coefficients are compared to their theoretical estimations by a semi-classical formalism. Even with a rough intermolecular potential composed of electrostatic and pair atom-atom interactions, the theoretical linewidths compare favourably with experimental results for both millimetre and infrared absorption.

Buffer-gas pressure broadening for the (0003)←(0000) band of N2O measured with continuous-wave cavity ring-down spectroscopy

“…4 along with the literature values for the m 3 and 2m 3 bands [4,6], and the pure rotational transitions [9][10][11][12][13][14]. Our results of the N 2 -and O 2 -broadening coefficients obtained for the 3m 3 band are in good agreement with the most of the literature values listed above.…”

“…The values of c decrease with jmj: a trend observed by our previous measurement and other groups conducting broadening measurements [3][4][5][6][7][8][9][10][11][12][13][14]22]. Based on the impact approximation, c is expressed from the cross-sections in the terms of the Weiskopf radius, the number density of the collision partner, and the mean relative velocity of the collision partner [29].…”

“…In their [6]), and 2m 3 (j, [4]) bands, and pure rotational transitions (., [9][10][11][12][13][14]). Theoretical results reported by Rohart et al [13]: total potential involving the atom-atom Lennard-Jones interactions in addition to electronic interactions of dipole, quadrupole, octopole, and hexadecapole (solid curves) or by neglecting in the electrostatic potential the octopole and hexadecapole moment of the absorber and the perturbers (dashed curves).…”

“…Parkes et al [8] reported for the 3m 3 band at 1.5 lm at room temperature. In addition, several measurements have also been performed for the pure rotational transitions of N 2 O in the J = 1-0 [9], 6-5 [10], 9-8 [11], 20-19, 24-23 [12], 22-21, 23-22 [13], , and 26-25 [14] transitions. In the present study, we have measured the pressure broadening coefficients in the 3m 3 band (1.52-1.53 lm) with various buffer gases (N 2 , O 2 , He, Ar, Ne, Kr and Xe) as a function of the rotational quantum number, and their temperature dependence (broadening exponent) with cavity ring-down spectroscopy (CRDS) using a tunable diode laser.…”

Recommended isolated-line profile for representing high-resolution spectroscopic transitions (IUPAC Technical Report)

“…However, a high-quality fit to a set of spectral lines is not a guarantee of the validity of the line-shape model used; in particular, in the binary-collision regime the fitted parameters have to be linear functions of the pressure [15,16,[34][35][36]. At the same time, multispectral fits [37,38] of lines recorded at several pressures of the perturbing gas are particularly useful for testing and characterizing complicated line-profile functions.…”