Gas phase photochemistry of carbon dioxide radical anion in water clusters

PHYS 381

Terefe Habteyes, terefeg@yahoo.com, Luis Velarde, lvelarde@email.arizona.edu, and Andrei Sanov, sanov@u.arizona.edu. Department of Chemistry, University of Arizona, 1306 E University Blvd, Tuscon, AZ 85721-0041
The photoexcitation of size-selected CO2(H2O)m, m=3-20 cluster anions at 355 nm causes either dissociation of the cluster core (CO2) or evaporation of water molecules. The dissociation and evaporation photo products have been determined to be O(H2O)m-k, 1≤k≤3, and CO2(H2O)m-k, 4≤k≤9, respectively. The dissociation channel dominates the fragmentation process in the m=3-7 range, while the latter takes precedence as the cluster size increases. The dissociation of CO2 is proposed to proceed via a hydration-stabilized excited state, originating from a low-lying 2B1 resonance in CO2. The 2B1 state is coupled with the ground 2A1 state by Renner-Teller interaction. Hence, the solvent-enabled Renner-Teller mediated predissociation is proposed as the mechanism for the formation of the O(H2O)m-k fragment anions. The electronic excitation of CO2 cluster core can also result in the evaporation of solvent molecules via energy transfer to vibrational degrees of freedom or via dissociation followed by geminate recombination of CO2.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Sci-Mix

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006