Abstract

Photoabsorption in large mass-selected cluster ions is detected via evaporation of molecules from the cluster. The shape and size evolution of the absorption spectrum with cluster size provides a mechanism to identify the chromophore and to detect the extent of charge delocalization in the cluster ion. Photofragment mass spectra have been obtained for ${\text{Br}}_2^{-}{\left({\text{CO}}_2\right)}_{\text{n}},{\text{I}}_2^{-}{\left({\text{CO}}_2\right)}_{\text{n}}\text{and}{\text{ICl}}^{-}{\left({\text{CO}}_2\right)}_{\text{n}}$ cluster ions following photoexcitation of the ${\frac{1}{2}}_{\text{g}} \left({}^2{\Pi }_{\text{g},1/2}\right)\leftarrow {\frac{1}{2}}_{\text{u}}\left({}^2{\Sigma }_{\text{u}}^{+}\right)$ transition in ${\text{I}}_2^{-}\text{and}{\text{Br}}_2^{-}$ and the analogous transition in ICl^-. Photodissociation of ${\text{X}}_2^{-}$ within the cluster results in the production of both X^-- and ${\text{X}}_2^{-}$-based ionic photofragments:

© 1994 Optical Society of America