Vibrational predissociation spectroscopy of the (H2O)6-•Arn, n≥6, clusters

Solvation of (H2O)(6)(-) with several argon atoms suppresses the strong direct photodetachment background in the bare hexamer anion, allowing vibrational predissociation spectroscopy to be: carried out in a background-free regime. In addition to the previously reported autodetaching resonances [C. G. Bailey, J. Kim, and M. A. Johnson, J. Phys. Chem. 100, 16782 (1996)] in the single donor hydrogen bonding region (similar to 3300 cm(-1)), the predissociation spectra reveal many weak bands scattered throughout the mid infrared (3200-3750 cm(-1)). Most of these new bands are evident in the bare hexamer spectrum after signal averaging, indicating that they are isolated using predissociation but not induced by solvation. The most intense bands display much stronger redshifts (> 30 cm(-1) by n = 15) than the matrix shifts typically found far the neutral water clusters, indicating that these bands are unique to the negative ion. (C) 1998 American Institute of Physics.