Time resolved studies of vibrational relaxation dynamics of CO(v=1) on metal particle surfaces

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Abstract
The vibrational relaxation dynamics of CO chemisorbed on small Pt and Rh particles supported on SiO2 has been investigated by picosecond time‐resolved infrared transient bleaching experiments. A vibrational T1 lifetime of ≊7 ps has been observed for several different samples, independent of polarization, pump intensity, and sample temperature from 100–400 K. A 1:3 isotopic dilution has no effect upon T1. This T1 lifetime is a factor of 10–50 times shorter than T1 reported for metal carbonyl cluster compounds in solution and on SiO2 supports. Two possible mechanisms are considered to account for the rapid T1 decay; redistribution of the energy throughout the broad CO vibrational band, and relaxation directly to electron–hole pairs in the metal particles.