15min:

MATTHEW VAN DUZOR, FOSTER MBAIWA, JIE WIE AND RICHARD MABBS, Department of Chemistry, Washington University, One Brookings Dr., Campus Box 1134 Saint Louis, Missouri 63130, USA.

Photoelectron imaging measurements of I^- CH₃CN are presented from the lowest energy I(²P_3/2) CH₃CN channel threshold to 0.3 eV above the I(²P_1/2) CH₃CN threshold. Excitation of the cluster just below the latter threshold leads to competition between direct detachment and the production of a dipole-bound state [I(²P_1/2) CH₃CN]^-. Subsequent relaxation of the I moiety (²P_1/2 ²P_3/2) occurs via autodetachment of the dipole bound electron. However, the autodetached electrons are energetically equivalent to those directly detached via the ²P_3/2 channel. While the photoelectron spectrum is insensitive to this phenomenon, the kinetic energy dependence of the photoelectron angular distribution (PAD) of the ²P_3/2 channel reflects these dynamics. Dramatic changes are observed within a 100 meV window of the I(²P_1/2) CH₃CN threshold. Although previously unreported, further results are presented that show sharp changes in the PAD are relatively common in I^- X cluster anions (X=polar molecule).