Rotational and vibrational dynamics of CO2 and N2O in helium nanodroplets

Infrared spectra are reported for carbon dioxide and nitrous oxide solvated in superfluid helium droplets, corresponding to the vibrational excitation of the (0201)/(1001) Fermi diad. Although the rotational constants of these two molecules are similar in the gas phase, they are observed to be quite different in liquid helium, namely, 0.154 cm−1 for CO2 and 0.0717 cm−1 for N2O. In addition, solvation in helium results in shifts in the vibrational origin that are in the opposite directions, −0.42 cm−1, for CO2 and +1.2 cm−1 for N2O. The spectra also show strong droplet size dependence, indicative of the interactions between the molecule and the liquid.