Vibrational lifetimes of surface hydroxyl groups of zeolites by picosecond IR pulses

Abstract

Vibrational lifetimes of the surface hydroxyl groups of zeolites (Y-type and mordenite) were measured in real time by pump-probe absorption spectroscopy using picosecond IR pulses. The relaxation lifetimes of the OH (ν=1) groups of Y-type zeolites which give the OH stretching bands at 3625 and 3540 cm −1 were 180 ± 12 and 63 ± 14 ps, respectively. The influence of the micro-structure of zeolites on the lifetime is discussed. For the surface OH groups of mordenite, the decay time of the transient hot band absorption at 3457 cm −1 (ν=2←1) was also measured by pumping the fundamental band at 3608 cm −1 to be 154 ± 18 ps, which agreed with 161 ± 18 ps obtained from the bleaching experiment of the fundamental band.