Stuttgart 2012 – scientific programme

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A: Fachverband Atomphysik

A 40: Poster: Ultra-cold atoms, ions and BEC

A 40.5: Poster

Thursday, March 15, 2012, 16:30–19:00, Poster.V

Cold, Magnetically-Trapped Br Atoms — William Doherty, •Jessica Lam, Christopher Rennick, and Tim Softley — Department of Physical and Theoretical Chemistry, Univeristy of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, United Kingdom

Photodissociation of molecular bromine near threshold produces a pair of bromine atoms that recoil along the polarization axis of the laser. At an appropriate wavelength, the velocity vector of one of the atoms can be aligned to exactly oppose the molecular beam velocity; this atom will then be stopped in the lab frame. The stopped atoms are probed by delayed multiphoton ionization. We have constructed a 300 mK deep magnetic trap with the field minimum at the intersection of the molecular beam with the photodissociation laser. The trap is filled from the photofragment velocity distribution, and the Br density accumulates with successive molecular beam pulses. We have developed a molecular dynamics model of the bromine atoms in the magnetic trapping field, including collisions with the molecular beam backing gas and vacuum chamber background pressure. This shows that, while a fraction of the atoms are lost through collisions with xenon, sufficient numbers are re-loaded on each shot to accumulate a steady-state density after a few seconds.