Mean square torque from linear molecule-rare gas atom systems at intermediate pressures

Abstract

From spectral moments of infrared vibration-rotation bands, the mean square torques are measured for COg, N20 and C2D 2 mixed with neon, argon and krypton and appear to be a linear function of the density up to 250 amagat. Above this density and up to 468 amagat, a departure from linearity is observed in the study of CO2-krypton mixtures.In the linear range, a Semi-empirical interrnolecular potential, proposed by Gordon, is used to interpret the results. This potential introduces an anisotropic parameter ~ for the repulsive forces. It is shown that ~ is dependent only on the active molecule. Moreover, it is concluded that the repulsive forces play a dominant part in the mean square torque.

A classical dynamics study of the anisotropic interactions in NNO–Ar and NNO–Kr systems: Comparison with transport and relaxation data

“…We have calculated the mean-square torque using Eq. ͑3͒ for the surfaces used here and compare them with the experimental results 15,16 in Table II. The agreement is good, which should be expected since the value of the parameter ␦ in the potential functions given by Eq.…”

“…Indeed, molecular beam electric resonance study of the NNO-Ar van der Waals molecule reveals an equilibrium structure with an angle very nearly 90°(87.4Ϯ1.5°), with the argon atom tilted slightly toward the oxygen atom. 1 Berreby and Dayan note that P 0 and P 2 symmetry is sufficient to fit the data, 15 suggesting that ͗C 2 ͘ may not be extremely sensitive to individual contributions of the Legendre expansion. Nevertheless, the lack of P 1 (cos ) symmetry in the proposed NNO-X potentials is an inherent flaw.…”

“…10,11 Pulsed Fourier transform microwave spectroscopy of a number of isotopomers of NNO-HCl provided good comparisons with ab initio calculations at the Moller-Plesset second-order ͑MP2͒ level, 12 and the nuclear quadrupole hyperfine structure due to both nitrogen nuclei in NNO-Ar and in NNO-CO2 is found to support the utility of quadrupolar nuclei in extracting geometrical information in such complexes. 13,14 Other spectroscopic data such as the mean-square torque have been measured for NNO-Ar and NNO-Kr, 15,16 and recently also for NNO-Xe and NNO-CO 2 , 17 and for NNO-SF 6 . 18 Furthermore, rotational relaxation rates for the Jϭ0 -1 transitions of 15 N 15 NO upon collisions with NNO, N 2 , Ar, Kr, and Xe have been determined by pulsed microwave time domain spectroscopy, providing the pressure dependence of the population and coherence decay rates 1/T 1 and 1/T 2 .…”

“…In this paper we consider the NNO-Ar and NNO-Kr surfaces proposed by Berreby and Dayan, which have the following form: 15 V͑R, ͒ϭ4⑀͕͑ /R ͒ 12 ͓1ϩ␦ P 2 ͑ cos ͔͒ Ϫ͑/R ͒ 6 ͓1ϩ␥ P 2 ͑ cos ͔͖͒, ͑1͒…”