Collisional broadening and shifting of the pure rotational Raman lines S₀(J = 0–4) of H₂ at room temperature

Abstract

The pressure broadening and shifting, of the S0(J = 0–4) pure rotational Raman lines of normal hydrogen, have been determined from 1 to 35 amagat units of density, at 29.8 °C. Over the range of densities explored, the width and shift of the lines are linear functions of the density. Our precise results may be reconciled with earlier measurements at higher densities by adding a term cubic in the density for the widths and quadratic in the density for the shifts. It is argued that the present results are safely within the impact regime and may be compared with calculations when they become available. The accuracy obtained is about 0.2 MHz per amagat [Formula: see text], for the broadening, and ranges from 0.1 to 0.3 MHz per amagat [Formula: see text] for the shifting coefficients. An analysis of the results indicate that it may be possible to combine the shifts of the pure vibrational and the pure rotational Raman lines to disentangle the contributions of the isotropic and anisotropic intermolecular forces to the perturbation of molecular spectra. Departures from linear broadening and shifting, at high density, are discussed.

Differential high-resolution stimulated CW Raman spectroscopy of hydrogen in a hollow-core fiber

“…This could be attributed to different effects such as collisional narrowing, pressure and wall broadening [21,22]. Compared to previous results [23] however, the lack of pressure dependence is quite surprising and is something we are currently investigating. The obtainable signal-to-noise ratio as a function of H 2 pressure inside the HC-PCF with typical parameters for the pump power (P 1064 = 300 mW) and the probe power (P 1135 = 1 mW).…”

Inverse R aman Spectrometry

“…In 1990 Rahn and Rosasco 51 published the results of a study on the dependence on temperature (up to 1000 K) and rotational quantum number, J (up to J D 5), of the Raman Q branch self-density-shift coefficients. Collisional broadening and shifting in the pure rotational spectrum in the range between 1 and 35 amagat were reported in 1994 by Le Flohic et al 52 A general approach to these phenomena, including both speed-and phase-changing collisions was published in the same year. 53 Spectra of H 2 perturbed by Ne, Ar, and Xe in the range between 395 and 800 K were recorded and analyzed in this paper.…”

Rotational time‐domain CARS in H2: departure from statistically independent collisional dephasing model

“…Taking D 3.3 ð 10 3 cm 1 amagat 1 for the broadening coefficient 11 and D 0 D 1.34 cm 2 amagat s 1 for the mass diffusion coefficient, 12 we obtain for the density min D k 2 D 0 / 1/2 at which  reaches its minimum  min D 2k D 0 / 1/2 D 2 min : min D 9 amagat and  min D 0.06 cm 1 (296 K). Just at a density of ¾9 amagat, Dicke narrowing was observed in the S 0 1 transition.…”