MICROWAVE SPECTRUM OF SULFUR DIOXIDE IN DOUBLY EXCITED VIBRATIONAL STATES AND DETERMINATION OF GAMMA CONSTANTS

The rotational spectra of the sulfur dioxide molecule in the excited states of overtones and combination-tones, 2ν1, 3ν2, 2ν3, ν1 + ν2, ν2 + ν3, and ν1 + ν3 were observed. From the rotational constants of each state, the second-order changes of the rotational constants by vibrations, γ11, γ33, γ12, γ23, and γ13, and the third-order change by ν2 vibration δ222 were determined. The determination of all the γss′ constants confirmed that the expansion of the rotational constants in terms of the vibrational quantum numbers converges rather rapidly for sulfur dioxide. The equilibrium structure of sulfur dioxide was refined and its uncertainty was discussed in detail. The effects of γss′ on the harmonic and anharmonic potential constants were also examined. © 1969.