Infrared Spectroscopy of Buffer-Gas Cooled Molecules and Dynamics of Bose Gases in Spherical Symmetry


Infrared absorption spectroscopy is a highly sensitive technique for probing molecular struc- ture, and when combined with cold molecular beam methods it provides unparalleled spectral resolution and absorption sensitivity to transitions in isolated gas-phase molecules. The first part of this dissertation investigates molecular beams of large polyatomic molecules produced via laser ablation of solid targets inside a buffer-gas cooling cell. Using matrix isolation spectroscopy to study the ablation products of graphite, we observe carbon clusters C3 to C12 produced at a rate of approximately 1011 - 1012 molecules for every pulse of the ablation laser. In a similar fashion, we study the production of metal oxide molecules with a buffer-gas beam source by ablating pure metal in the presence of O2 gas, and find consistent production of the WO molecule. Finally, we discuss efforts towards high resolution rotational-vibrational spectroscopy of WO in the gas phase.

The investigation of collective modes in ultracold atomic gases provides revealing information about the nature of interactions in these systems. Of particular interest is the interplay between a Bose-Einstein condensate and thermal excitations present at finite temperature, which effect the dynamics of collective modes by shifting mode frequencies and introducing damping. The second part of this dissertation investigates the dynamics of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap recently developed at JILA. Through numerical simulations within the Zaremba-Nikuni-Griffin formalism, we identify the beating between two eigenmodes of the system, corresponding to in-phase and out-of-phase oscillations of the condensed and noncondensed portions of the gas. This beating leads to nonexponential collapse of the amplitude of the condensate oscillation, followed by a partial revival. Results of the simulations are shown to agree well with experimental data.

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Department of Physics
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University of Colorado Boulder
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