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

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.