The Mid- and Near-Infrared Spectra of Water and Water Dimer Isolated in Solid Neon

Spectra have been obtained between 700 and 8000 cm−1 for H216O, and between 700 and 5000 cm−1 for deuterium and/or oxygen-18-enriched water, trapped in solid neon at approximately 5 K. Samples with Ne:water mole ratios between 400 and 6400 were studied. As in the heavier rare-gas solids, isolated water molecules can undergo relatively free rotation in solid neon, and nuclear spin equilibration is slow. The observed spectra can be explained by postulating excitation from the two lowest rotational levels of the water molecule. Absorptions of nonrotating water are also present in the spectrum. The matrix shifts for water isolated in a neon matrix are much smaller than those reported for water in matrices of the heavier rare gases. Absorptions contributed by the H- or D-donor moiety of (H2O)2, (HDO)2, and (D2O)2 have also been identified and assigned.