Infrared vibrational predissociation spectra of large water clusters

Abstract

The infrared absorption spectrum in the OH stretching region of (H 2O) 19 clusters formed in a supersonic molecular beam is reported. It was obtained with mass-spectrometric detection and is compared with a similarly obtained spectrum of (H 2O) 6 and a large-cluster spectrum obtained with bolometric detection. The mass-resolved spectra show a broad absorption band between ≈ 3200 and 3600 cm −1, reminiscent of the H-bonding feature in acondensed phase spectrum. The spectrum via the bolometer is peaked to the blue of this region, suggesting that the level of H-bondingis much lower. Mass resolution is clearly advantageous in selectively obtaining spectra of large clusters, free of interferencefrom smaller ones.