Water-chain clusters:: vibronic spectra of 7-hydroxyquinoline•(H2O)n, n = 1-4

Mass- and isomer-selected S-1 <-- S-0 resonant two-photon ionization spectra of the series of supersonically cooled 7-hydroxyquinoline . (H2O)(n), n = 1-4 clusters are reported. These represent a series of hydrogen-bonded "water-chain" clusters, strung between the -O-H group and the N atom of the aromatic molecule. The vibronic spectra of n = 2 and 4 clusters are strongly overlapped with the n = 3 spectrum, and are identified for the first time; all exhibit large red-shifts (approximate to 2000 cm(-1)). The n = 2 and 3 clusters form solely water-chain clusters, while n = 4 exists as water-chain clusters and as three other isomers, as shown by UV/UV laser-holeburning. (C) 1999 Elsevier Science B.V. All rights reserved.