Fourier Transform Microwave Spectroscopy of Tropolone Direct Transitions between the Proton Tunneling Doublet Levels
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Date
1992
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Publisher
Ohio State University
Abstract
In our previous study of tropolone with a conventional source-modulated microwave spectrometer, more than 300 lines were observed in the frequency range of 28 $\sim$ 85 GHz and were identified as $\alpha$-type rotational transitions within the $O^{+}$ and O states, where $O^{+}$ and O denote the lower and upper level of the proton tunneling doublet, respectively. The spectrum was subtantially affected by an interaction, $\Pi - F(J_{a}J_{b} + J_{b}J_{a})$, between the $O^{+}$ and $O^{-}$ states. The analysis of the perturbation gave us the proton tunnelling splitting in the ground state $\Delta_{0} = 29 282 \pm 90$ MHz as well as the interaction constant $F = 16.378 \pm 0.081$ MHz. In the present study, direct transitions between the proton tunneling doublet levels in the ground state were observed with a pulsed Fourier transform microwave spectrometer. Twenty three b type P- and Q branch transitions between the 0 and $0^{+}$ states were observed in the frequency region of 8 $\sim$ 15 GHz. Six $\alpha$-type rotational transitions within the $O^{+}$ and $O^{-}$ were also observed. The proton tunneling splitting in the ground state $\Delta_{0}$ was revised as 29 193.788 $\pm$ 0.026 MHz from an analysis of the present results combined with those by our conventional microwave study. The rotational and centrifugal distortion constants for both the $O^{+}$ and $O^{-}$ states were also obtained precisely together with the interaction constant $F = 16.456 \pm 0.015$ MHz. The effective dipole moment along the a axis was determined to be 3.428 $\pm$ 0.050 D and 3.438 $\pm$ 0.050 D, respectively, for the $0^{+}$ and $^{-}$ states from the measurement of the Stark effects. The errors correspond to three times the standard deviation in the fit.""
Description
Author Institution: Department of Chemistry, Faculty of Science, Kyushu University 33; Department of Pure and Applied Science, College of Arts and Science, The University of Tokyo