The IR absorption spectra of water monomer and clusters are reproduced in the OH stretching region. Spectra are recorded at with the samples of (a) , (b) , and (c) . The numbers correspond to the number of water molecules in the clusters. The broad bands marked by the asterisks are assigned to the water dimer and trimer in the loose substitutional trapping sites.
The IR absorption spectra of water monomer and clusters are reproduced in the OH bending region. Spectra are recorded at with the samples of (a) , (b) , and (c) . The numbers correspond to the number of water molecules in the clusters. The proton-acceptor and proton-donor molecules of the water dimer are indicated as PA and PD, respectively. The peak marked by the asterisk is assigned to the water dimer in the loose substitutional trapping sites.
The bonded OH stretching frequencies of water clusters, from the dimer to the hexamer, in the gas phase, liquid He droplets, and rare gas matrices (Ne, Ar, Kr, and Xe) are plotted as a function of of the matrix materials. The main peaks of the water cluster are denoted by the open circles, while the additional weak bands due to the water dimer and trimer trapped in Xe matrices are shown with the filled circles.
The water dimers isolated in the trapping sites of (a) Ar and (b) Xe matrices are represented using the van der Waals radii and assuming the face-centered cubic (fcc) crystal structures.
The O–O distances are plotted as a function of the cluster shifts of the bonded OH stretching bands of water clusters with , relative to the bonded OH stretching band of the water dimer. The values of the O–O distances are taken from Ref. 36. The filled squares denote the gas phase data (Ref. 1) while the filled and open cycles are the Ar and Kr matrix data in this study, respectively. The solid lines are obtained by fitting the data by an exponential function. The vertical broken lines indicate the frequency shifts of the observed water dimer and trimer bands in Xe matrices, relative to the hypothetical line position of the water dimer expected by the linear relation to .
Observed positions of the rovibrational lines of monomer trapped in Kr and Xe matrices. The available literature data are also given for comparison.
Comparison of the bonded OH stretching frequencies of clusters in the gas phase, liquid He droplets, and various rare gas matrices. All numbers are given in .
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