# Spectra of the D2O dimer in the O-D fundamental stretch region: vibrational dependence of tunneling splittings and lifetimes

## TL;DR

This study investigates the vibrational dependence of tunneling splittings and lifetimes in the D2O dimer's O-D stretch region using high-resolution spectroscopy, revealing detailed vibrational effects on tunneling dynamics and lifetimes.

## Contribution

It provides detailed experimental data on tunneling splittings and lifetimes in the D2O dimer's vibrational states, including excited states and mixed isotopologues, with high spectral resolution.

## Key findings

- Tunneling splittings decrease in excited states.
- Lifetimes vary from 0.2 to 5 nanoseconds depending on vibrational state.
- Observation of a tentative combination mode involving intramolecular and intermolecular vibrations.

## Abstract

The fundamental O-D stretch region (2600 - 2800 cm-1) of the fully deuterated water dimer, (D2O)2, is studied using a pulsed supersonic slit jet source and a tunable optical parametric oscillator source. Relatively high spectral resolution (0.002 cm-1) enables all six dimer tunneling components to be observed, in most cases, for the acceptor asymmetric O-D stretch, the donor free O-D stretch, and the donor bound O-D stretch vibrations. The dominant acceptor switching tunneling splittings are observed to decrease moderately in the excited O-D stretch states, to roughly 75% of their ground state values, whereas the smaller donor-acceptor interchange splittings show more dramatic and irregular decreases. Excited state predissociation lifetimes, as determined from observed line broadening, show large variations (0.2 to 5 nanoseconds) depending on vibrational state, K-value, and tunneling symmetry. Another very weak band is tentatively assigned to a combination mode involving an intramolecular O-D stretch plus an intermolecular twist overtone. Asymmetric O-D stretch bands of the mixed isotopologue dimers D2O-DOH and D2O-HOD are also observed and analyzed.

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Source: https://tomesphere.com/paper/1903.06596