High resolution spectroscopy of gas phase free radicals

Abstract

Laser Induced fluorescence has been used to obtain spectra of diatomic free radicals. The structure observed was examined in greater detail by two high resolution techniques, microwave optical double resonance and intermodulated fluorescence.
The first molecule studied was CuF for which recording of a previously unobserved sub-band has allowed conclusive identification of the upper state in the yellow system as b3π. The hyperfine structure has been examined and the seven constants determined are interpreted in terms of the electronic configurations which could give rise to a 3π state. The lambda doubling and spin-rotation parameters are compared with calculated values based on perturbations due to the a3∑+ state.
The ground state microwave spectrum of the CH radical has been observed for the first time in the laboratory. These measurements have been used to determine improved lambda doubling and hyperfine constants, and make accurate predictions for possible astrophysical observations. The A2◿ state has been examined in detail and effects due to the very small lambda doubling in this state observed. A fourth order perturbation treatment is used to obtain calculated values for comparison. The three proton hyperfine parameters for the 2◿ state have been determined and it is shown that the wavefunction involves a significant hydrogen Is contribution.
Initial, but so far unsuccessful attempts to observe the ground state microwave spectrum of SiH by MOOR are also described.

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