The electronic structure and photochemistry of the O 2n -(H 2O) m, n 1-6, m 0-1 cluster anions is investigated at 532 nm using photoelectron imaging and photofragment mass-spectroscopy. The results indicate that both pure oxygen clusters and their hydrated counterparts with n 2 form an O 4 - core. Fragmentation of these clusters yields predominantly O 2 - and O 2 -H 2O anionic products, with the addition of O 4 - fragments for larger parent clusters. The fragment autodetachment patterns observed for O 6 - and larger O 2n - species, as well as some of their hydrated counterparts, indicate that the corresponding O 2 - fragments are formed in excited vibrational states (v 4). Yet, surprisingly, the unsolvated O 4 - anion itself does not show fragment autodetachment at 532 nm. It is hypothesized that the vibrationally excited O 2 - is formed in the intra-cluster photodissociation of the O 4 - core anion via a charge-hopping electronic relaxation mechanism mediated by asymmetric solvation of the nascent photofragments: O 4 - → O 2 -(X 2 g) O 2(a 1 g) → O 2(X 3 g -) O 2 -(X 2 g). This process depends on the presence of solvent molecules and leads to vibrationally excited O 2 -(X 2 g) products.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry