Effects of spectral density on the azide vibrational transition in water versus D2O

Water and D2O have distinct spectral densities resulting from isotopic shifts associated with their vibrational manifold. Two-dimensional infrared, pump-probe, and transient grating spectroscopies were employed to directly measure the vibrational dynamics for the azide transition of NaN3 within solutions of water and D2O. Although the frequency correlation time revealed minimal variation, a linear correlation between lifetime and the optical density of the solvent background was uncovered. Thus, a predictive model of the lifetime was proposed. These findings highlight the importance of spectral density of the solvent and its role in the pathways of energy dissipation for vibrational probes.