Formation, Dynamics, and Applications of Ultracold Molecules

University Of Connecticut, Storrs CT

Investigators

Abstract

This grant enables the PIs to continue and expand their research program on the formation, dynamics, and applications of ultracold molecules at sub-miliKelvin temperatues. Prior research by the group has focused on diatomic alkali molecules produced by the process of ultracold photoassociation, in which pairs of ultracold alkali metal atoms are associated into bound vibrational levels of electronically excited molecular states. These electronically excited molecules then decay by spontaneous emission of light, some to near-dissociation rovibrational levels of the singlet ground state (the X state) or the metastable triplet state (the a state). New experiments will focus on methods to efficiently create KRb and Rb2 molecules in the lowest rovibrational levels of both the stable X state, X(v=0, J=0), and the metastable a(0,0) state. The program also includes related studies of radiative lifetimes and collisions. Two promising methods for continuous and simple production of X(0,0) are: (1) resonance-enhanced coupling of two different electronic states, one with long-range character to enhance photoassociation and the other with short-range character to enhance decay to X(0,0); (2) Feshbach-Optimized Photoassociation (FOPA) in a magnetic field to greatly enhance photoassociation rates by mixing of high levels of the X and a states, again to enhance the short-range character of the wave function. For the metastable a(0,0) state, a novel "blue-detuned" photoassociation scheme can produce large populations, and is being used to study the purely radiative lifetime at low density as well as inelastic and reactive collisions in an optical trap. By trapping ultracold molecules at high densities, the group seeks to observe for the first time ultracold atom-molecule photoassociation. This will produce ultracold triatomic molecules such as Rb3 and KRb2 in previously unexplored excited states, which can be detected either by laser ionization or autoionization. Interest in X(0,0) molecules is particularly strong because only in this quantum state can it be assured that collisions will not cause heating due to changes in the internal quantum state. This enables long trapping times and investigations of subtle quantum interactions. Possible applications of cold polar molecules for quantum information are of great current interest, and at high enough densities even a molecular Bose-Einstein condensate becomes a possibility. The new production methods explored in this project offer large advantages in simplicity over alternative approaches such as Raman transfer in quantum degenerate gases, and they enable continuous or near-continuous generation of cold molecules. Systematic studies of the spectroscopy and dynamics of these cold molecules will provide much-needed data and physical insights to inform future investigations of both ultracold and room-temperature molecules. The project will be well-integrated into the large ultracold physics program at the University of Connecticut, currently including seven faculty and about 40 students and postdoctoral fellows. Elements of this integration include project-based group meetings, mentoring, workshops, seminars, and numerous national and international collaborations. Presentations by our research group members locally and at meetings and other educational institutions contribute to scientific understanding. Broader long term benefits include new understanding and applications in areas such as ultracold chemistry, measurements of fundamental symmetries and physical constants, quantum information science, and nanoscience, as well as improved international collaboration.