Collision effects in the nonlinear Raman response of liquid carbon disulfide

Abstract

Electronic polarization effect on low-frequency infrared and Raman spectra of aprotic solvent: Molecular dynamics simulation study with charge response kernel by second order Møller-Plesset perturbation method A model of the polarizability of carbon disulfide dimers was constructed, using polarizabilities from accurate time-dependent density functional theory calculations as reference. This direct reaction field model takes dipole-induced dipole effects, induced multipole effects and effects due to the overlap of the electronic clouds into account in an approximate way. The importance of the induced multipole and the overlap effects is investigated. This polarizability model is subsequently used to calculate the third-order time-domain Raman response of liquid carbon disulfide. These results are compared to experimental data and earlier calculated response in which only dipole-induced dipole effects on the polarizability were included. The multipole effects are found to give a significant contribution to the subpico second part of the third-order Raman response.

Fifth-order two-dimensional Raman spectroscopy: A new direct probe of the liquid state

“…A fully quantum mechanical treatment of real liquids is impossible at present and is likely to remain so for many years. On the other hand, exact classical MD simulations are tenable and have been carried out for liquid xenon and liquid carbon disulphide and water in order to evaluate the fifth-order response [6,15,21,22,[97][98][99]. These microscopically based approaches will be discussed in section 4.…”

“…The fifthorder response was treated using multimode Brownian oscillator (MMBO) models [2,31,84,93] as well as instantaneous normal modes analysis [5,15,20,92]. More recently, coupled-mode theory has been employed to generate the fifth-order response of an atomic liquid [16,17,[94][95][96] while direct molecular dynamics (MD) simulations have been carried out for both atomic and molecular liquids [6,15,21,22,[97][98][99][100]. This section describes the basic formulation of the fifth-order response function and some simple harmonic models to illustrate the sensitivity to the underlying dynamics.…”

The Effect of Induced Multipoles on the Fifth-order Raman Response

“…They were optimized in order to give as good agreement with time-dependent density functional theory (TDDFT) calculations on various dimers. 47 The two components of dipole-octupole polarizability, which is the first non-vanishing multipole polarizability was also calculated using TDDFT and can be compared to the one obtained for a single molecule in the DRF model. The isotropic polarizability used for carbon disulfide is 8. in the DRF model applied.…”

“…All these models and calculations have been described more thoroughly in our earlier paper considering the effects in the third-order Raman response. 47 In order to interpret the two-dimensional spectra the response have been calculated using these four different models and comparing the results allows to examine the origin of the fifth-order response.…”

“…43,45,46 In previous work we investigated these effects in the interaction between carbon disulfide molecules and their impact on the third-order response. 47 Both effects from the dipole-induced dipole effect and the induced multipole effects, where found to affect the third-order response. In dimers the polarizability at short ranges as those found in the first solvation shell in carbon disulfide the electron cloud overlap effects were also found to be significant, while their effect on the third-order response were less pronounced.…”