Subpercent agreement between ab initio and experimental collision-induced line shapes of carbon monoxide perturbed by argon

Abstract

We present fully ab initio calculations of second-overtone rovibrational line shapes of carbon monoxide perturbed by argon. The quantum mechanical scattering problem between CO and Ar is solved numerically for two different ab initio interaction potentials. We use the generalized Hess method to determine spectroscopic cross sections which describe the effect of collisions on each spectral line. Using these cross sections, we determine the line-shape parameters that we use to generate the Hartmann-Tran and speed-dependent billiard ball profiles. We compare the generated line shapes with high-quality experimental line profiles of five lines measured at five pressures between 0.01 and 1 atm. A subpercent agreement over the entire pressure range is obtained. Calculations for the P(9) line are used to inspect the effects of the two interaction potentials. The discrepancies for both the considered interaction potentials and the experiment are explained within the described theoretical framework. The presented results are the most accurate collisional line-shape calculations for a system with collision dynamics representative of atmospherically relevant species.

Ab initio investigation of the CO–N2 quantum scattering: The collisional perturbation of the pure rotational R(0) line in CO

“…We note that at large kinetic energies the dependencies are linear on the log-log plot. This type of relation has already been reported in the studies of the argon-perturbed CO lines 122,149,150 as well as in the studies of the Ar-perturbed CO 2 151 or H 2perturbed N 2 152 isotropic Raman lines. Moreover, it is seen from Fig.…”

“…120,121 Recently, subpercent agreement with the experimental shapes of Ar-perturbed rovibrational lines in CO was achieved. 122 Here, we report the ab initio quantum scattering calculations of the collision-perturbed shape of the molecular line for a system that is relevant for the terrestrial atmosphere. We investigate the width of the N 2 -perturbed pure rotational R(0) line in CO. Scattering calculations are performed using three PESs.…”

Toward measurements of the speed-dependence of line-mixing

“…[3][4][5][6]) which enable predictions of non-Voigt effects (including the influences of both the speed dependences and the collisioninduced velocity changes) on the profiles of collisionally-isolated lines with a typical accuracy of a few 0.1% (e.g. [4,[7][8][9][10]). Concerning the line-mixing (LM) process, its effects on spectra have been experimentally and theoretically studied for decades [1,2].…”

CO-Ar collisions: ab initio model matches experimental spectra at a sub percent level over a wide pressure range

“…The success of this approach was recently demonstrated by the example of the simplest cases corresponding to collisions of H 2 with He [11][12][13], HD with He [14] and D 2 with D 2 [10]. To advance further in this direction, the approach was recently used for the study of collisions between the CO molecule and Ar based on the shapes of two and five rovibrational transitions in the P branch of the fundamental and second-overtone bands, respectively [15,16]. The unprecedented subpercent level of consistency between theory and experiment achieved in these studies evidences that ab initio calculations can provide reliable data for spectroscopic databases widely used by various applications.…”