Knowledge Bank

More than a hundred lines of the rotational spectra of $(CH3)2SO$ and $(CD3)2SO$ were measured and assigned in the region of 5.5 to 55 KMc. The difficulties in the first assignment were overcome by using a Stark-absorption cell, inner dimension $10\times 47$ mm, which gave a good resolution of the Stark patterns up to high J. Series of q-lines, b-type transitions, were traced first by building up difference schemes with their frequencies assisted by regularities of the Stark-effect, later by a computer program based on Kivelson-Wilson centrifugal theory. Check of assignment was made by using the spectroscopic combination principle. From the six rotational constants a $r0-structure$ was calculated. The dipole moment and its orientation were measured. Slight internal rotation splitting was observed at lines with $J⩾14$.