The intensities of low-energy electronic absorption transitions of some carbonyls and thiocarbonyls

The intensities of low-energy electronic transitions for some carbonyls and thiocarbonyls have been calculated from CNDO wavefunctions. Quite good agreement with experimental results has been obtained, where the latter are available. A satisfactory approximation for calculating intensities employs only one-center integrals. From the calculated trends in oscillator strengths, the absorption of thiophosgene at 4.46 eV can be identified as the pi--> pi(* 1)A(1) <-- <(X)over tilde>(1)A(1) system. Another, very weak, system of thiophosgene at approximate to 3.9 eV is tentatively assigned to an n --> pi*1A1 <-- <(X)over tilde>(1)A(1) transition, with the n orbital localized on the chlorine atoms.