VIBRATIONAL-ENERGY REDISTRIBUTION IN CP-ASTERISK-IR(CO)2 (CP-ASTERISK=ETA(5)-PENTAMETHYLCYCLOPENTADIENYL) STUDIED BY BROAD-BAND TRANSIENT INFRARED-SPECTROSCOPY

Picosecond vibrational energy dynamics involving the symmetric (2020 c m-1) and asymmetric (1953 cm-1) CO-stretching modes of CpIr(CO)2 in r oom temperature n-hexane is measured using mode specific infrared exci tation followed by broadband infrared multichannel probing to generate a transient spectrum. The recovery of the transient bleaching and abs orption bands, following 2020 or 1953 cm-1 excitation, yields a upsilo n = 1 CO-stretching lifetime T1 = 28 +/- 7 (1sigma) ps. The transition s from upsilon = 7 vibrational states give rise to new absorption feat ures in the transient spectra at 2008, 1994, 1941 and 1930 cm-1. The t ime evolution of these absorption monitors rapid energy redistribution and equilibration (< 10 ps) between the symmetric and asymmetric CO-s tretching modes prior to ground state recovery.