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IQSE AMO/QO LUNCH SEMINAR SERIES


"Exotic Behavior of H Atoms Embedded in Solid Ne/H2 Mixtures and Pure H2 at Temperatures below 1 K"


Dr. Sergei Sheludiakov
Texas A&M University

ABSTRACT 

Quantum properties are best manifested by the lightest of elements: helium and hydrogen. Light atomic impurities, H, introduced into solid molecular hydrogen turned out to be delocalized even at temperatures below 1 K and able to migrate along the H2 crystal by a repetition of the exchange tunneling reaction, H+H2→H2+H, even though their recombination is strongly suppressed [1,2].

In the present talk I will summarize our recent results on studies of hydrogen atoms in Ne/H2 solid mixtures and a pure H2 matrix carried out in high magnetic field, 4.6 T, and temperatures 0.1-1 K. Our main experimental techniques are high-frequency (128 GHz) electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) [3].

In our experiments with the Ne/H2 solid mixture samples which appeared to be highly disordered and porous we observed formation of H2 clusters even at extremely low, 100 ppm, H2 admixtures. We also observed an astonishingly high recombination rate of H atoms in such H2 clusters at temperatures 0.3-0.6 K which provides evidence of solid-liquid transition in such H2 aggregates [4].

In the recent experiments with H atoms in pure H2, we observed formation of a high nuclear polarization of H atoms which strongly exceeds the value expected for the Boltzmann statistics. Possible scenarios for explaining this exotic behavior will be discussed.

Finally, I will briefly describe the new experimental cell and our future experimental plans.

References: [1] T. Kumada, Phys. Rev. B 68, 052301 (2003); [2] S. Sheludiakov, J. Ahokas, J. Jarvinen, D. Zvezdov, L. Lehtonen, O. Vainio, S. Vasiliev, D. M. Lee, and V. V. Khmelenko, Phys. Chem. Chem. Phys. 18, 29600 (2016); [3] S. Sheludiakov, J. Ahokas, O. Vainio, J. Jarvinen, D. Zvezdov, S. Vasiliev, V. V. Khmelenko, S. Mao, D. M. Lee, Rev. Sci. Instrum. 85, 053902 (2014); [4] S. Sheludiakov, J. Ahokas, J. Jarvinen, L. Lehtonen, S. Vasiliev, Yu. A. Dmitriev, D. M. Lee and V. V. Khmelenko, Phys. Rev. B 97, 104108 (2018).



September 11, 2018
IQSE 578, 12:00 Noon
Mitchell Physics Building


Institute for Quantum Science and Engineering
Texas A&M University


Pizza to be served 30 minutes prior start time