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Cold molecules promise to open important new scientific directions such as precise control of chemical reactions, novel dynamics in cold collisions, long-range collective quantum effects, quantum information processing, precision measurement, and new insights for condensed matter physics. Here we report our groupTMs research efforts on the application of cold molecules for precision measurement.
In the first experiment, cold, stable, ground state polar molecules are produced from Stark decelerators. Hydroxyl radicals (OH) and formaldehyde (H2CO) molecules have been bunched in phase space, accelerated, slowed, or trapped. We demonstrate acceleration/deceleration of a supersonic beam of OH to a mean speed adjustable between 550 m/s to rest, with a translational temperature tunable from 1mK to 1K, corresponding to a longitudinal velocity spread from 2 to 80 m/s. These velocity-manipulated stable bunchOSC contain 104 to 106 molecules at a density of ~ 105 to 107 cm-3 in the beam. These slow, cold molecular packets are ideal for high resolution microwave spectroscopy. The lowest λ-doublet lines of OH are measured with an order of magnitude improvement in accuracy. These results have led to improved understandings in the molecular structure. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10-6 for measuring the potential time variation of the fundamental fine structure constant over 10 billion years. In the second experiment, with ultracold 88 Sr confined in a one-dimensional magic wavelength optical lattice, we have performed narrow line photoassociation spectroscopy near the 1S0-3P1 intercombination transition. The nature of the narrow transition in the 88Sr atoms stimulated by highly coherent light made it possible to detect with high resolution nine least-bound vibrational molecular levels associated with the long-range Ou and 1u potential energy surfaces. It also favored the decay of the excited molecules into tightly bound and stable ground-state molecules trapped by the optical lattice. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss. The application of ultracold Sr2 molecules for constraining the time-variation of proton-electron mass ratio will be discussed. Finally, we will present a theory study on efficient production of ultracold ground state molecules by applying the principles of coherent accumulation and control to photo-association. |
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