The rotational analysis of a 1A''-1A' band system of thiazyl fluoride

The band system of NSF with origin at 25 487 cm-1 (3923 Å) has been photographed in absorption at high dispersion. Rotational analyses have been carried out for four bands including the 0-0 band. The bands have type-c polarization, corresponding to an electronic transition 1A''-1A'. The geometry for the excited state is r0(NS) = 1·56 Å, r0(SF) = 1·63 Å and ∠ NSF = 101·6°, the principal changes on excitation being an increase in NS bond length of 0·11 Å and a decrease in valence angle of 15·3°. This change in angle is contrasted with those for the lowest excited states of other molecules with 18 valence electrons.