The electron resonance spectra of the gaseous radicals SF and SeF have been detected and analyzed. The derivation of an effective Hamiltonian which operates in the rotational subspace of the ground vibronic state is described. Use of this Hamiltonian yields the rotational constants, the fine-structure splittings, and the axial components of the 19F hyperfine interaction for both radicals.

The 4875 A band of glyoxal has been photographed in absorption under high resolution and a rotational analysis carried out. The band is of type C fnd the principal mqlecular constants are:, vo = 20 507.57 cm-'. The A-rotational constants are smaller by a factor of -2 than the constants found earlier for trans glyoxal. The new results are consistent with the assignment of the band to an allowed 'B1-'Al (n*-n) transition of cis glyoxal. Temperature studies indicate that the cis isomer lies 1125 , 100 cm-' above the trans isomer. This is the first time that cis glyoxal has been detected experimentally.

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The electron resonance spectra of the J = 3/2 and J = 5/2 rotational levels of the 2 II 3/2 state of SeH and the J = 3/2 rotational level of the 2 II 3/2 state of SeD are described. Values of the rotational constant and Λ-doubling parameters are determined. Evidence is found for a tensorial interaction of the spin and magnetic field, arising from the gauge invariance requirement of the spin-orbit coupling Hamiltonian. Hyperfine structure from 77 Se is observed, and the hyperfine coupling constants are determined. The effect of an electric field on the spectra is analysed and the electric dipole moment determined.