Observation and study of the 4(3)Delta(g) state in potassium and electromagnetically induced transparency (EIT) with emphasis on the open molecular system

This work highlights both the importance of accurate knowledge of molecular energy levels and their use for demonstration of coherence effects, which can be used to control absorption of light.{09}In the first part we report the observation of the 43Δ_g state in diatomic potassium. The 43Δ_g state has been investigated using perturbation-facilitated optical-optical double resonance (PFOODR). Molecular constants, the potential energy curve, and the Franck-Condon table for the 43Δ_g↔b3Π _u transitions are given. The observed data is consistent with the energy eigenvalues calculated from the Rydberg-Klein-Rees (RKR) potential energy curve. The RKR curve is also compared, and is consistent, with the ab initio potential energy curve. The electronic assignment is confirmed through a quantum defect calculation and Rydberg labeling. Vibrational and rotational assignments are confirmed through resolved fluorescence data including polarization dependence of the fluorescence. In the second part of this thesis we report electromagnetically induced transparency (EIT) in a molecular system with two co-propagating laser beams using a cascade excitation scheme and diatomic lithium and sodium molecules as sample molecules. The open character of molecular systems is discussed in conjunction with this EIT scheme with emphasis on the role of the residual Doppler width as it takes on a new meaning. Simulations of corresponding experimental spectra have been included and are in good agreement with the experimental data. The simulations suggest a value for the lifetime of the 41&Sgr;_g+ (v = 0, J = 17) state in Na₂ of 3.0(4) ns.