OBSERVATION AND ANALYSIS OF THE $1^{1}\Delta$ STATE OF $^{6}Li_{2}$

Author Institution: Physics Department, University of New Brunswick; Laboratoire de Spectrometrie Ionique et Mol\'{e}culaire, Universit\'{e} Claude BernardAs part of a continuing investigation into the electronic states of $Li_{2}$ in the $30,000 cm^{-1}$ region, we have recently excited the $F^{1}\Sigma_{g}^{+}$ state of $^{6}Li_{2}$ via two separate, single frequency double resonance transitions, $X^{1}\Sigma_{g}^{+} \rightarrow A^{1}\Sigma_{u}^{+} \rightarrow F^{1}\Sigma g^{+}$, using a single mode dye laser operating in the DCM dye region. The resulting fluorescence has been examined, at high resolution, using a Fourier Transform spectrometer. In addition to several known electronic transitions that appear in the spectrum, we observed a highly congested, complex, blue degraded transition in the $8300 - 8600 cm^{-1}$ region. The lower state was found to be the $B^{1}\Pi_{u}$ state and the upper state which has never previously been observed, was assigned as $1^{1}\Delta_{g}$. The complexity of the spectrum results from the almost identical rotational and vibrational constants of the two states. The $1^{1}\Delta_{g}$ state is excited via collisionally induced energy transfer from the $F^{1}\Sigma_{g}^{+}$ state. The assignment and rotational analysis of the transition will be presented and the $1^{1}\Sigma_{g}^{+}$ state. The assignment and rotational analysis of the transition will be presented and the $1^{1}\Delta_{g}$ state will be discussed in terms of its molecular parameters, dissociation products and the excitation mechanism responsible for its formation."