Infrared laser spectroscopy of diacetylene and cyclopropane in helium nanodroplets

High resolution infrared laser spectroscopy has been used to obtain rotationally resolved vibrational spectra of diactyelene and cyclopropane in helium nanodroplets. In part, this work was motivated by the need for a large database of rotational constants for molecules solvated in liquid helium. Data of this type provides benchmarks with which to test the theoretical methods that are currently being developed for calculating the effect of the helium on the rotational dynamics of these solvated molecules. In general, the correlated motion of the helium and the molecule results in an effective moment of inertia that is considerably larger than that of the gas phase molecule.