D. M. Lee:  Abstract for mid-day seminar, March 22.


Exotic Magnetic Resonance Properties of Atomic H Free Radicals Embedded in Solid H2:  to BEC or not to BEC?


Reference         J. Ahokas, et al. PRL 97, 095301 (2006)


Co-workers     J. Ahokas, J. Jarvinen and Sergey Vasiliev, U. of Turku, Finland, Vladimir Khmelenko and David M. Lee, Cornell University




            We present the first magnetic resonance study of atomic hydrogen embedded in solid H2 films 50 nm in thickness for temperatures 150-900 mK.  We found that at T ≈ 150 mK average concentrations of H atoms of order 1018 cm-3 are very stable against recombination during two weeks of observations.  The distribution of the population of the two lowest hyperfine states is found to be non-Boltzmann, with a very large occupation of the ground state.  We consider the possibility of formation in solid H2 of regions with high local concentrations of H atoms, where collective quantum phenomena such as Bose-Einstein Condensation (BEC) might occur.  Another curious observation was that although the nuclear spin-lattice relaxation time for the transition between the two lowest hyperfine levels was very long (many hours), it was impossible to completely saturate this transition.  This is in marked contrast to the conventional wisdom in magnetic resonance research!