The mass-selected [(CO 2) 2(H 2O) m] - cluster anions are studied using a combination of photoelectron imaging and photofragment mass spectroscopy at 355 nm. Photoelectron imaging studies are carried out on the mass-selected parent cluster anions in the m=2-6 size range; photofragmentation results are presented for m=3-11. While the photoelectron images suggest possible coexistence of the CO 2 -(H 2O) mCO 2 and (O 2CCO 2) -(H 2O) m parent cluster structures, particularly for m=2 and 3, only the CO 2 - based clusters are both required and sufficient to explain all fragmentation pathways for m≥3. Three types of anionic photofragments are observed: CO 2 -(H 2O) k, O -(H 2O) k, and CO 3 -(H 2O) k, k≤m, with their yields varying depending on the parent cluster size. Of these, only CO 2 -(H 2O) k can potentially result from (O 2CCO 2) -(H 2O) m parent structures, although an alternative mechanism, involving the dissociation and recombination of the CO 2 - cluster core, is possible as well. The O -(H 2O) k and CO 3 - (H 2O) k channels are believed to be triggered by the dissociation of the CO 2 - cluster core. In the CO 3 -(H 2O) k channel, seen only in the range of m=3-6, the CO 2 - core dissociation is followed by an intracluster association of nascent O - with the solvent CO 2. This channel's absence in larger clusters (m > 6) is attributed to hindrance from the H 2O molecules.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry