IDENTIFICATION OF TRIPLET LEVELS BY ZEEMAN STUDIES OF MICROWAVE-OPTICAL DOUBLE-RESONANCE IN THE (A)OVER-TILDE(1)A(2)-(X)OVER-TILDE(1)A(1) SYSTEM OF THIOFORMALDEHYDE

Microwave-optical double resonance experiments have been carried out i n the presence of magnetic fields on the 4(0)(1) band of the ($) over tilde$$ A(1)A(2)-($) over tilde$$ X(1)A(1) system of thioformaldehyde. Several anticrossings have been observed. The series of levels 6(06), 7(07),....12(012) of the 4(1)A(1)A(2) state is shown to be perturbed by the 6(33), 7(34)....12(39) levels of the 2(1)3(1) ($) over tilde$$ a(3)A(2) state. Two anticrossings involving high vibronic levels of th e ground state (X levels) are explained by interactions with the 8(5) level of the 2(1)4(2) ($) over tilde$$(3)A(2) state.