MULTIPLE RESONANCE SPECTROSCOPY OF THE $G^{1}\Pi_{g}$ AND $F^{1}\Sigma^{+}_{g}$ STATES OF $^{7}Li_{2}$ DETECTION OF PREDISSOCIATING $F^{1}\Sigma^{+}_{g}$ STATE LEVELS THROUGH ATOMIC SIDE FLUORESCENCE

Author Institution: Physics Department, Temple University; Department of Modern Applied Physics, Tsinghua UniversityOptical-Optical Double Resonance (OODR) was employed to excite rovibrational levels in the unknown upper portions of the G(1)$^{1}\Pi_{g}$ and F(4)$^{1}\Sigma^{+}_{g}$ states. Although both are singlet states and dissociate to the same atomic limit (2p+2p) they behave in significantly different ways. Vibrational levels as high as v = 48, which has rotationless energy within 1% from the dissociation energy, were observed in the $G^{1}\Pi_{g}$ state by detecting molecular fluorescence. In the $F^{1}\Sigma^{+}_{g}$ state all levels in the energy region above 2s+3s atomic limit were found to the strongly predissociated. This is due to interactions with the continuum of the $E^{1}\Sigma^{+}_{g}$ state which at long internuclear distance dissociates to the 2s + 3s atomic limit. Because of the very short lifetimes these levels were detected using atomic side fluorescence. A $C_{5}$ coefficient was determined from the last few outer turning points of the experimental RKR potential curve of the $G^{1}\Pi_{g}$ state. Rotational and vibrational dependence of the line width for the predissociated $F^{1}\Sigma^{+}_{g}$ state levels was investigated and a preliminary RKR curve which covers 99.6% of the potential well has been derived from experimental data