High resolution infrared spectra of a carbon dioxide molecule solvated with helium atoms

Helium clusters containing a single carbon dioxide molecule, He _N-CO₂ were analyzed using high resolution infrared spectroscopy in the region of the v₃ fundamental band. A pulsed supersonic jet expansion and a tunable infrared diode laser probe was utilized in the experiment. On the basis of the evolution of the spectra as a function of jet backing pressure and temperature, spectral lines were assigned as R(0), P(2), and R(2) transitions. The band origins showed a linear blueshift up to N=5, followed by a monotonic redshift, consistent with a model forcing He atom density to be located closer to the ends.