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T. LIANG, P. RASTON AND G. E. DOUBERLY, Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556.
Trans-HOOO and HOOO-(O2)n clusters have been assembled in helium nanodroplets and probed with a tunable narrow linewidth PPLN-OPO laser system in the O-H stretching region. We observed the
1 band at 3569.45 cm-1, which consists of rotationally resolved a- and b-type components, in addition to the broad c-type
1+
6 band at 3699.06 cm-1. The band origins for
1 and
1+
6 are shifted to the blue by only 0.15 cm-1 and 1.03 cm-1, respectively, compared to the gas phase values by Lester and co-workers., Neither of the two other predicted stable isomers, namely cis-HOOO and the hydrogen-bound OH-O2 species, were found within a broad survey scan. The HOOO-(O2)n clusters grow in to the red of the
1 band of trans-HOOO as the O2 pick-up pressure is increased. Cluster signals are resolved for up to n = 4, while signals for clusters with n > 4 pile up to form a broad feature. High level ab initio multireference calculations are needed to help understand the geometries for these multiple O2 clusters. The O-D stretch of trans-DOOO was measured at 2635.02 cm-1, which is extremely close to the gas phase value at 2635.06 cm-1. The linewidths of the transitions within this band are narrower than those within the O-H stretching band of trans-HOOO, which suggests that the lifetime of the excited vibrational state is longer for trans-DOOO than trans-HOOO.