Laser cooling and trapping of atoms have revolutionized atomic physics with the realization to cool and trap atoms into the ultra-cold regime. This has led the precision of spectroscopy on atoms to an unprecedented level, which make cold atoms not only platforms to search for new physics and test fundamental laws of nature, but also ultra-precise tools to measure fundamental physical quantities such as time and magnetic fields. Cooling and trapping molecules into the cold and ultra-cold regime foresees similar revolutions. The rich internal energy structure and large permanent electric dipole moments of molecules enable a variety of applications beyond the realm of cold atoms, including searches for the electron electric dipole moment, studies of ultra-cold chemistry, and realizations of strongly interacting quan- tum many-body systems. However, the complex energy structure of molecules also render them difficult to laser cool and trap, especially at high densities. In this thesis, we present our progress on pursuing laser cooling and trapping of a new species, aluminum monochlo- ride(AlCl). The highly diagonal Franck-Condon factors(FCFs) and high scattering rate with large single photon recoil velocities owning to a cycling transition at DUV wavelength range make it a favorable candidate. We present our absorption spectroscopy on the A1Π ← X1Σ+ transition to extrapolate the molecular constants and estimate the Frank-Condon factors, and our effort to study the various targets for laser ablation production of AlCl to optimize its initial production. We also present our in-beam fluorescence spectroscopy to resolve the relevant hyperfine structure in the A1Π state in order to understand and construct optical cycling schemes.
Following the successes obtained with using lasers to cool and trap atoms, the same principles are being applied to molecules. Finding a molecule that is amenable to laser-cooling is not trivial. Aluminum monochloride (AlCl) has been proposed as a viable candidate for laser-cooling and trapping due to predicted large Franck-Condon factors and short excited state lifetime, allowing for efficient imparting of momentum from photons. To be efficiently slowed, multiple electrons must be cycled between the ground and excited states. This thesis presents a detailed derivation of the hamiltonian terms that must be understood for the X1Σ+ ↔ A1Π transition in AlCl. Initial absorption spectroscopy measurements are performed on the transition, yielding measurements of molecular constants. From these constants, the Franck-Condon factor for the cycling transition is determined to be 0.9988, which is ideal for cycling. The choice chemical compound that is ablated to produce AlCl for these experiments is not trivial. It is found that a mixing aluminum and potassium chloride with a molar ratio of 1:1.55 produces the optimal yield of AlCl. Additionally, a magneto-optical-trap apparatus is discussed and tested here on ytterbium. This test resulted in the successful trapping of neutral ytterbium, marking the creation of the first magneto-optical-trap at the University of California, Riverside. The vibrational and rotational properties of AlCl clearly make it a strong candidate for laser-cooling and trapping, however there are still many challenges that must be overcome before such experiments can be successful.
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