IR spectroscopy of CO in helium droplets

What is it about?

Spectra of carbon monoxide (CO) molecules solvated in helium droplets are presented. Spectroscopic constants are derived. Unknowns are eliminated by isotopic substitution. CO is found to rotate slower in liquid helium than in the gas phase. The apparent increase in the effective moment of inertia is attribute to coupling to phonons which are supported in larger helium dropelts.

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Why is it important?

CO is an important model to investigate the molecular interaction in liquid helium droplets. In this experimental-theoretical investigation it was shown that molecular rotation can interact with phonons (breathing mode of droplets) leading to an increase in the effective moment of inertia and spectral line width.