Far-infrared laser-sideband measurements of the amidogen radical, NH2, near 2 THz with microwave accuracy
Abstract
The rotational spectrum of the NH2 radical has been studied with the frequency stabilized Cologne Sideband Spectrometer for Terahertz Applications (COSSTA) between 1.78 and 2.00 THz with measurement accuracies of 50-200 kHz. The highly precise new data on amidogen serve to test our model of the NH2 rotational spectrum based on all field free pure rotational transitions previously available and to improve predictions of the spectrum for low to moderate N which are of relevance to future astrophysical observations. Overall, 31 lines of eight rotational transitions with 2≤N≤9 and 0≤Ka≤4 have been newly recorded, including the 423-330 transition around 535 GHz. Besides the present data and the ones used in our previous study, also ground state combination differences from an investigation of the A2A1-X2B1 electronic transition have been included in the fit. In all, 798 lines with N and Ka≤18 were used. Many spectroscopic constants of our previous global fit of all field-free pure rotational transitions have been improved, and some new constants were needed to fit the input data within experimental uncertainties. The total number of independent spectroscopic constants determined is sixty-three and includes fine and hyperfine structure constants.
- Publication:
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Journal of Molecular Structure
- Pub Date:
- December 2001
- DOI:
- 10.1016/S0022-2860(01)00839-0
- Bibcode:
- 2001JMoSt.599..293G
- Keywords:
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- Rotational spectrum;
- Centrifugal distortion;
- Hamiltonian;
- Far infrared laser sideband spectrometer;
- Amidogen;
- NH2;
- Interstellar molecule