Microwave spectrum of the inversion-rotation transitions of the D3O+ ion: k = 3n interaction and equilibrium structure

Abstract

Ground state inversion—rotation transitions of the fully deuterated hydronium ion, D3O+, were observed by microwave spectroscopy. Fifty three P- and Q-branch transitions were measured precisely for the lowest pair of inversion doublets in the frequency region of 220 to 565 GHz. Inclusion of Δk = ±3n interactions in the Hamiltonian was essential for a full explanation of the observed lines, with measurement uncertainty of 20 to 60 kHz. The molecular constants, including C, for the 0+ and 0− levels, as well as the Δk = ±3n interaction parameters, were determined from this complete fitting to the data. The inversion splitting was determined to be 15.355 503 38(107) cm−1, where the number in parentheses denotes one standard deviation of the fit. Since a harmonic potential of H3O+ is available, zero-point corrections to the rotational constants of H3O+ and D3O+ were calculated and the zero-point averaged (r z) structures were derived from the zero-point corrected rotational constants. The results are as follow...