Simulation and theory of vibrational phase relaxation in the critical and supercritical nitrogen: Origin of observed anomalies

Abstract

We present results of extensive computer simulations and theoretical analysis of vibrational phase relaxation of a nitrogen molecule along the critical isochore and also along the gas-liquid

The fundamental vibrational shift of HCl diluted in dense Ar and Kr

“…Raman bands is a solvent dependent effect which allows to obtain interesting insight about the diatomic-solvent intermolecular interactions, and the static properties of the solvent [4][5][6][7]. In this sense, while the isotropic part of the diatomic-solvent interaction has very poor effects on the spectral profile of the fundamental infrared band, the vibrational shift is very sensitive to this component of the interaction potential, and so it is an useful tool to get complementary information to the line shape studies.…”

Simulation study of solvent shifts of vibrational overtone spectra

“…As discussed by Everitt and Skinner [10] and others [8,9,11], to obtain the correct sign of the solvent shifts requires including the dependence of the atomatom LJ parameters N, N , N, N , N, Ar and N, Ar on the N 2 bond length, for the purpose of calculating the solvent-induced bond force F 1 ðXÞ ¼ ð@Vðx, XÞ=@xÞ x¼0 and force-constant F 2 ðXÞ ¼ ð1=2Þð@ 2 Vðx, XÞ=@x 2 Þ x¼0 . Roughly, this models the dependence of the nitrogen atom charge density and polarizability on bond length [21].…”

“…For the LJ site-site model intermolecular potential with two sites on N 2 , analytic expressions have been derived [10,11] for the quantities F 1 ðXÞ and F 2 ðXÞ required for the calculation of the mean frequency shift (7). These are used as inputs to our analysis program which forms the averages F 1 and F 2 from the MD trajectory data for X(t) for rigid molecules generated by the program DL_POLY_2 [22].…”

“…To get even the correct sign for the solvent shifts (red for the N 2 fundamental at standard state conditions [6,7]) requires careful tuning of the intermolecular potential [8][9][10][11]. We use an existing Lennard-Jones (LJ) site-site model for the N 2 -N 2 intermolecular interactions [10,11] which traces its origins to an earlier model of Cheung and Powles [12], and a similar model for the N 2 -Ar interactions [13].…”

“…To get even the correct sign for the solvent shifts (red for the N 2 fundamental at standard state conditions [6,7]) requires careful tuning of the intermolecular potential [8][9][10][11]. We use an existing Lennard-Jones (LJ) site-site model for the N 2 -N 2 intermolecular interactions [10,11] which traces its origins to an earlier model of Cheung and Powles [12], and a similar model for the N 2 -Ar interactions [13]. The Cheung-Powles potential is modified by allowing the intermolecular atom-atom (sitesite) parameters (well depth) and (diameter) to depend on the N 2 intramolecular bond length; when the bond stretches due to intermolecular interaction, electron charge density shifts from the internuclear bonding region to the atoms, thereby changing the effective atom parameters and .…”