Vibrational relaxation of the free terminal hydroxyl stretch in methanol oligomers: Indirect pathway to hydrogen bond breaking

Ultrafast time-resolved transient infrared absorption spectroscopy was used to measure dynamics following excitation of the OD stretch in nonhydrogen bond donating OD groups of MeOD molecules in CCl₄. At low MeOD concentrations, it was found that the signals decay exponentially via vibrational relaxation with a 2.15 ps time constant. At higher MeOD concentrations, vibrational relaxation following excitation of the free OD mode led to hydrogen bond dissociation. Reformation of the hydrogen bonds occurred on two distinct time scales, 22 ps and ≫300 ps.