Physics & Astronomy Colloquium

3:30 PM, Friday, March 10, 2006

Room 155, Chem-Phys Building

Dr. Jun Ye

Joint Institute for Laboratory Astrophysics (JILA)
National Institute of Standards and Technology, Boulder
Department of Physics, University of Colorado, Boulder

``Cold molecules --- Stark deceleration and precision spectroscopy''

Cold, stable, ground state polar molecules can now be produced from a Stark decelerator. After supersonically cooled in both the internal and external degrees of freedom, hydroxyl radicals (OH) and formaldehyde (H₂CO) molecules have been bunched in phase space, accelerated, slowed, or trapped using time-varying inhomogeneous electric fields to control the molecular motion via their Stark energy shifts. Based on our experimental capabilities we have proposed a novel method for controlling a class of low temperature chemical reactions. Specifically, we show the hydrogen abstraction channel in the reaction of H₂CO and OH (H₂CO + OH → CHO + H₂O) can be controlled through either the molecular state or an external electric field.

Using slow, cold OH radicals, we have performed precise measurements of the ground-state, λ-doublet microwave transitions, with at least a tenfold improvement in precision. 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 (Δα/α) over 10¹⁰ years.

Refreshments will be served in CP 155 at 3:15 PM