Molecular spectroscopy and quantum control of homonuclear alkali dimers

The focus of the research presented in this dissertation is twofold. First, I will report the results of a spectroscopic study on two previously unobserved, highly excited Σ𝑔1+ and Π𝑔1 electronic states of the cesium dimer. The rovibrational structure of these states was probed using the optical-optical double resonance (OODR) technique in which 133Cs2 molecules from thermally populated levels in the 𝑋 Σ𝑔1+ ground state were excited through intermediate levels of either the 𝐵1Π𝑢 state or the mixed 𝐴1Σ𝑢 +~𝑏3Π𝑢 manifold to the target states. Probe laser resonance frequencies were determined through the detection of laser induced fluorescence (LIF) from the target states to the 𝑎3Σ𝑢+ triplet ground state of the dimer. Using ab initio results from our collaborators and considering selection rules for dipole-allowed transitions, the two experimentally observed states were identified as the 11Σ𝑔1+ and 61Π𝑔 states of the cesium dimer, respectively. The Dunham-RKR method was utilized to generate experimental potential energy curves for the two states. Second, I will discuss the experimental realization of a method of generating state selective molecular angular momentum orientation/alignment in neutral, nonpolar 7Li2 using dressed states created by an intense continuous wave (cw) optical field. This all-optical experiment utilized three single longitudinal mode cw lasers to excite thermal gas phase lithium molecules via a four-level excitation scheme. A strong, near-resonant coupling laser E-field was used to induce either 𝑀- or |𝑀|-dependent Autler-Townes splitting in the spectra, conditional on the type of laser polarization utilized. Depending on the choice of excitation pathway, coupling laser rotational branch, and laser iv polarization used, all or certain 𝑀 or |𝑀| levels could be isolated in the resulting spectrum, depending on desired result. Thus, these techniques can be used to effectively control the orientation/alignment of a molecular population’s angular momentum in a specific electronic state. These results mark the first time all-optical 𝑀-sublevel selectivity has been achieved in nonpolar molecules.