Electron resonance of SO ( 3 Ʃ ) in the gas phase

The electron resonance spectrum of SO has been previously shown to arise from SO in two electronic states, the ground 3 Ʃ - and the excited 1 ∆ state. In this paper the portion of the spectrum assigned to the 3 Ʃ - state is analysed and shown to arise from three isotopic species, 32 S 16 O, 33 S 16 O, and 34 S 16 O. The analysis shows that besides the dominant interaction of the unpaired electronic spins with the magnetic field; other interactions must be taken into account to interpret the spectrum accurately. Interactions with electronic orbital angular momentum of π states mixed in by spin-orbit coupling and with rotationally induced magnetic moments have been observed. Values for parameters measuring such interactions have been determined from the spectrum, and these values lead to a resolution of the first- and second-order contributions to the zero-field molecular constants as well as an approximate value for the spin-orbit coupling constant. The hyperftne structure resulting from 33 S in 33 S 16 O has also been observed and is related to the usual hyperfine coupling constants. The expected line strengths and widths for SO have been calculated and these are compared with the observed quantities. Besides the expected lines from the isotopic SO species in the 3 Ʃ - state, several other lines have been detected. These lines are interpreted as arising from 32 S 16 O in the ground electronic state, but in the first excited vibrational level. The spectrum of vibrationally excited SO allows a value of the spin-spin coupling constant in the first excited vibrational state to be determined.

Electron resonance of electronically excited SO( 1 ∆) in the gas phase

The gas phase reaction between carbonyl sulphide and the products of a microwave discharge in molecular oxygen has been studied by electron resonance. In addition to absorption lines from O 2 and SO in their ground electronic states, a four-line pattern due to SO in its excited 1 ∆ state is observed. Analysis of this spectrum yields the rotational constant B 0 for the 1 ∆ state, from which the bond length is calculated to be 1·493 Å.

Microwave spectroscopy of nonlinear free radicals III. High field Zeeman effect in HCO and DCO

Transitions involving low rotational levels of the HCO and DCO radicals in their ground states have been detected by tuning them to a frequency of about 9 GHz with an external magnetic field. The variation of electric dipole intensity with applied flux density is discussed and the transitions most likely to be detected in a fixed frequency/swept field experiment are characterized. The resonance fields are primarily determined by the size of the spin-rotation interaction. Analysis of the experimental data permits the determination of the dominant component of the spin-rotation tensor, Є aa , as 11.6176(14) GHz for HCO and 7.1253(17) GHz for DCO. The transition fields are relatively insensitive to the anisotropy of the electron spin g -tensor.

The e.p.r. spectrum of vibrationally excited hydroxyl radicals

The e. p. r. spectrum of vibrationally excited hydroxyl radicals in levels v = 1, 2, 3 and 4 of the 2 II 3/2 ground state has been observed in the reaction between hydrogen atoms and ozone in the gas phase. Although the variation of ∧ -doubling with vibrational energy superficially agrees well with the ‘pure precession’ model of Van Vleck, there is clear evidence that the matrix element <II│ L y │ ∑> decreases considerably with increasing internuclear distance. The form of the decrease in the hyperfine coupling constants with increasing vibrational energy agrees well with that deduced from Kayama’s theoretical calculations.