The collision-induced polarized and depolarized Raman spectra of helium and the diatom polarizability

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Abstract
The spectral distributions and absolute intensities of collision‐induced Raman spectra of helium are obtained at 30 amagat, with incident beam polarizations parallel and perpendicular to the observation. These spectra can readily be separated into the polarized and the depolarized Raman continuum of the helium diatom. For comparison, spectra are also computed from wave mechanics, on the basis of Placzeck’s polarizability theory. Accurate, semiempirical interaction potentials are used as input, together with ab initio computations of the helium diatom polarizability tensor components. The computed spectra of selected trace and anisotropy functions agree with the observed polarized and depolarized continua. Anisotropy functions consistent with the depolarized spectrum differ by less than 5% from the classical dipole‐induced dipole (DID) values at 2.685 Å separation.