Infrared spectra and intensities of H$_{2}$O-N$_{2}$, H$_{2}$O-O$_{2}$ and H$_{2}$O-Ar complexes in superfluid He droplets.

The infrared spectra of H$_{2}$O-N$_{2}$, H$_{2}$O-O$_{2}$ and H$_{2}$O-Ar complexes in superfluid He droplets were measured in the range of the stretching vibrational bands of water molecules. The infrared intensities of anti-symmetric stretching band of these complexes showed no significant increase with respect to that of a single H$_{2}$O molecule as opposed to the predicted intensities in previous theoretical calculations. From the analysis of the observed spectra, it was found that H$_{2}$O in H$_{2}$O-O$_{2}$ and H$_{2}$O-Ar rotates nearly freely inside the complexes, while that in H$_{2}$O-N$_{2}$ does not. The conformation of these complexes were estimated from the rotational constants obtained from the analysis.