ROTATIONALLY RESOLVED LIF SPECTRUM OF $\tilde{A} ^{2}A_{1} \leftarrow \tilde{X} ^{2}E$ TRANSITION OF $CH_{3}S$ AND THE $\tilde{A} ^{2}A_{1}$ STATE SPIN-ROTATION CONSTANT OF $CH_{O}$

$^{1}$ Y. Endo, S. Saito, and E. Hirota. J. Chem. Phys. 85. 1770 (1986).Author Institution: Laser Spectroscopy Facility. Department of Chemistry, The Ohio State University; Institute of Atomic \& Molecular Science, Academia Sinica.; Department of Chemistry, Florida State UniversityThe rotationally resolved laser - induced fluorescence spectrum $\tilde{A} ^{2}A_{1} \rightarrow \tilde{X} ^{2}E$ of the methylthio radical has been obtained in a free-jet supersonic expansion. A detailed rotational analysis of the electronic transition has been carried out. A joint least square fitting of the present electronic transitions and previously observed microwave $transitions^{1}$ yields ground and excited state molecular constants. The ground state constants are considerably revised from those previously reported, while the excited state values have been accurately determined for the first time in this experiment. Particularly interesting are the very large values of the ground state spinrotation constants in $CH_{3}S$ and $CH_{3}O.$ To develop more understanding of the spinrotation interaction in these radicals, a high resolution LIF spectrum of $\tilde{A} ^{2}A_{1} \rightarrow \tilde{X} ^{2}E$ transition of $CH_{3}O$ has been taken and the upper state spin-rotation constants have been determined