The microwave spectrum of thietan-2,2,4,4-d₄

Abstract

The microwave spectrum for thietan-2,2,4,4-d₄ is analysed in six of its lowest puckering states and up to J = 25. The close lying pairs of states of v _p = 0/1, 2/3 and 4/5 are treated with a vibration-rotation hamiltonian which includes an off-diagonal coupling term in v _p. Additional corrections to this coupling term in higher powers of the angular momentum operator are derived and their importance for improving the fit of calculated to observed data is tested. The variation of the centrifugal distortion constants with v _p follows the model of Creswell and Mills (1974, J. molec. Spectrosc., 52, 392). A value is determined for the derivative with respect to the puckering coordinate of the ac-component of the inverse moment of inertia tensor.