Photoassociation spectroscopy of ultracold and Bose-condensed atomic gasses.

摘要

This thesis will discuss high precision photoassociation spectroscopy of ultracold rubidium, both in a thermal cloud and in a Bose condensate, and techniques to produce and detect ultracold molecules. Experiments were conducted in laser-cooled ultracold dilute gas atom samples that were prepared in magneto-optic traps then transferred either to a far off-resonant optical dipole force trap or a magnetic trap.; First, the atomic radiative lifetime of the Rb 5P state was measured using photoassociative spectroscopy in an optical dipole trap. The first ∼50 bound states of the “pure long-range” $0-g$, 52S_1/2 + 52P _3/2 state in both 87Rb₂ and 85Rb ₂ were observed. Analysis of the binding energies of these states followed by fitting to a long range potential including retardation and exchange led to a determination of the radiative 87Rb 5P lifetime to be 26.24(7) ns.; High precision stimulated Raman photoassociation was performed in a Bose-Einstein condensate of 87Rb, resulting in the observation of several of the most weakly bound 87Rb₂ states. The binding energies of these molecular levels were determined to a precision of better than 10 kHz and even down to ∼1 kHz. The nearly zero kinetic energy of atoms in a Bose condensate allowed the precise measurements. Analysis of these states led to the first measurement of the second-order spin-orbit interaction in ultracold 87Rb collisions and the determination of the very nearly complete Rb-on-Rb ultracold scattering picture.; Finally, photoassociative techniques were used to produce a sample of cold molecules, which were trapped in a magnetic trap. The molecules were then directly detected via resonant multi-photon ionization. The molecules produced had two components in the trap lifetime: a quickly decaying component in which 99% of the molecules decayed in ∼10 ms, followed by a long lived component that persisted for up to 150 ms.