Date of Award
Doctor of Philosophy (PhD)
Charles I. Sukenik
Gail E. Dodge
Creating ultracold molecules has attracted considerable interest in the last decade. Once created, such molecules can be used for precision spectroscopy or to study chemical reactions at ultracold tem peratures. Several techniques have been developed to produce ultracold molecules; the most common is photoassociation where two ultracold atoms collide in the presence of light that induces a free-bound transition to an excited molecular state. Photoassociation can also be used to perform spectroscopy in order to map out the ro-vibrational levels of a molecular state. In this dissertaiotn, we report on our Photoasociative Spectroscopy (PAS) studies conducted separately in argon and krypton. For each species, we have studied transitions near two different atomic limits ns[3/2]2 —> np[5/2]2 and ns[3/2]2 —» np[5/2]3where n = 4 for argon and n = 5 for krypton. The former atomic transition is called the “quench transition” since it forms a strong coupled channel to the ground state. As a result for this strong coupling the original atomic sample is degraded and quenched. The latter transition is the one used to cool and confine the atoms and is known as the “trapping transition.” Spectroscopy near the trapping transition in argon was studied previously in our group  and specific features were observed in the spectrum. At the time, the features were not definitively identified, but more than one explanation was suggested for further testing. One possible explanation was that these features were a result of resonances happening at “doubly-excited” molecular levels. The population of such states could take place as a result of absorbing two photons of the same frequency which causes photoassociation. In this dissertation we report on a series of experiments that were performed to study and conclusively identify the origin of those features. These experiments led to the conclusion that the features in the spectra were an artifact of otherwise undetectable frequency sidebands on our semiconductor diode laser. Once identified as such, a new laser was constructed to repeat the spectroscopy measurements in argon and take new measurements in krypton that would be free from laser artifacts. In those spectra, no specific vibrational features were observed and resolved in either species. Results were consistent with published results obtained by other groups using other noble gases. Finally, we report on our attempts to perform PAS on a quench transition in order to confirm results obtained for krypton by another group . We were not able to observe any photoassociation signal for both argon and krypton on this transition. We were able to observe similar effects to those reported in Ref.  but we attribute these to artifacts from an acousto-optic modulator and not as arising from molecular structure.
Omar, Maha K..
"Photoassociative Spectroscopy of Ultracold Argon and Krypton Confined in a Magneto Optical Trap"
(2015). Doctor of Philosophy (PhD), dissertation, Physics, Old Dominion University, DOI: 10.25777/a743-4154