Microwave spectrum of theKa= 1 ← 0 rotation-tunnelling band of (D2O)2

Publisher Website
Google Scholar
Abstract
A 78–118 GHz synthesizer-driven backward-wave oscillator is used together with klystron sources and frequency doublers to measure the electric-resonance optothermal spectrum of the K a = 1 ← 0 rotation-tunnelling subband of (D2O)2. Transitions are observed originating from each of the six tunnelling states, A+ 1, B+ 1, E+ 1, A- 2, B- 2, and E- 2, allowing an estimate of the largest tunnelling matrix element h 4v, characterizing the separation of the A+ 1, B+ 1, and E+ 1 states from the A- 2, B- 2, and E- 2 states. We find the average of h 4v for the K a = 0 and 1 states to be ∼ -8 943 MHz. A comparison of the K a = 1 ← 0 band origins for the A/B states with the band origin for their E partner gives h 2v ∼ -6·9 MHz, where h 2v is the tunnelling matrix element responsible for the displacement of the E symmetry levels from the center of their interconversion split A/B partners. Values found for the A rotational constant, A ∼ 124 923 MHz, and h 2v are in good agreement with those obtained from the submillimetre measurements of Zwart, E., ter Meulen, J. J., and Meerts, W. L., 1990, Chem. Phys. Lett., 173, 115, on the K a = 2 ← 1 band of the complex. Estimates are presented for the potential barriers to the 1 → 2, 1 → 5 and 1 → 7 tunnelling processes.