Rotational and vibrational dynamics of H2O and HDO in helium nanodroplets

High-resolution infrared spectra have been obtained in the 2.7 μm region of water monomer, solvated in superfluid helium nanodroplets. A total of five ro-vibrational transitions have been identified for the ν3 bands (OH stretch) of H2O and HDO. The associated Lorentzian line widths fall in the range 0.05–2.0 cm−1 (FWHM). The electric field induced Q(0) transition of HDO has also been observed. In the latter case the broadening appears to be inhomogeneous, with a line width of 0.007 cm−1. The line widths for the various transitions correlate with the available rotational energy in the excited state, relative to the energies of the elementary excitations of the liquid helium.