NSF Materials World Network: Quantum Phenomena In Atomic Hydrogen Stabilized In Solid Molecular Hydrogen
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TECHNICAL SUMMARY This Materials World Network project will be focus on two main thrusts: (i) further studies of H atoms in molecular H2 films as well as D atoms in D2 films at lower temperatures, and (ii) extension of the work on impurity-helium condensate samples to lower temperatures and higher concentrations. Techniques will be modified to attain higher concentrations of H and D atoms in an attempt to observe Bose-Einstein condensation (BEC) of H in H2 and Pauli paramagnetism in D and D2 films. The mm wave studies of H atoms at T < 1 K in thin and thick films of molecular H2 will be continued, with emphasis on careful temperature dependence measurements of the magnetization for samples prepared under different conditions in order to identify the cause of the non-Boltzmann behavior of the populations of the two lowest hyperfine states previously observed below 1 K. In addition a quartz microbalance will be utilized to test for superfluid behavior at low temperatures, a manifestation of BEC. A search will be made for changes in the Raman Spectrum associated with BEC. The ongoing research will include further studies of impurity-helium condensates containing hydrogen atoms, deuterium atoms or mixtures of H and D atoms in and on clusters of Kr and other noble gases. X band pulsed and CW ESR will be employed to study the magnetic relaxation behavior and the distribution of H and D atoms in and around the nanoclusters. NON-TECHNICAL SUMMARY Confirmation of the occurrence of Bose-Einstein condensation for H atoms moving through a solid molecular hydrogen crystal would be an important example of Bose-Einstein condensation in a periodic structure. Furthermore, mixed samples of H and D atoms contained in molecular matrices are excellent systems for the study of low temperature chemical reactions through the process of exchange quantum tunneling. Studies of impurity- helium condensates composed of assemblages of nanoclusters tie in nicely with studies of other forms of soft condensed matter. The impurity-helium condensates provide a means of storing large amounts of chemical energy which is released when the atoms combine to form molecules. This Materials World Network project clearly crosses the boundary between physics and chemistry and may provide valuable clues for practical energy storage systems. Further advances in millimeter wave technology being developed for ultralow temperature magnetic resonance will be useful in many other areas of science. The collaborative programs will benefit greatly from extended visits of graduate students, post docs and senior researchers between the partner laboratories. This project is supported by the Condensed Matter Physics program and the Office of Special Programs in the Division of Materials Research.