Theoretical study of the three-body absorption spectrum in pure rare gas fluids

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Abstract
The three-body induced dipole resulting from ternary collisions among identical atoms is calculated within the framework of the one effective-electron model of Jansen. It is found that at short and intermediate range, the main contribution comes from dioles induced by exchange quadrupole moments (EQID). Moreover, a rough estimate shows that the long-range dispersion contribution to the three-body dipole is negligible for (He)3 but becomes significant for (Kr)3. In order to investigate the nature of a spectrum due to triplet interactions, a molecular dynamics simulation taking into account only the EQID mechanism is performed to generate the translational absorption spectrum in gaseous and liquid krypton. In the liquid, the correlation function exhibits two time scales; a fast decay corresponding to the mean duration of exchange quadrupoles, and a slower decay, lasting several ps, which is associated with translational diffusion. A very rough estimate of the expected absorption in liquid krypton is also given.