SPECTROSCOPY OF ACETYLENE TRIPLET STATES BY DIRECT OPTICAL EXCITATION

We present here initial results of the first experiments detecting direct optical (uv) excitation of spin-forbidden transitions from the singlet ground electronic surface $(S_{0})$ of acetylene into the low-lying molecular triplet manifold ($T_{1}$, $T_{2}$). The metastable states thus populated are detected via electron ejection from a Cs metal surface (SEELEM: Surface Electron Ejection by Laser Excited Metastables spectroscopy). Initial insights into the structural and dynamical properties of these states, and the mechanism of the SEELEM detection process, are discussed.