科研之友
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摘要
He-4 and He-3 films adsorbed in nanoporous silicates have shown similar heat capacities until the quantum-fluid layer appears at coverages over the first-layer completion n (1). To obtain information on dynamics of adatoms at low coverages below the quantum fluid region, we have done pulsed-NMR experiment at 3.3 MHz for He-3 films adsorbed in straight 2.4 nm nanochannels of FSM silicates. The spin-lattice and spin-spin relaxation times T (1) and T (2) observed at 0.54-7 K were well described by the two-dimensional version of the Bloembergen-Purcell-Pound model. At coverages 0.4-1.7n (1), minima of T (1), indicating the spin correlation time tau (c) of 4.8x10(-8) sec, were observed at temperatures between 6 and 3 K. With decreasing temperature, changes in T (1) and T (2) become small below about 1.5 K, suggesting crossover from thermally-activated motion to quantum tunneling. In contrast to large variations below n (1), both relaxation times above n (1) are almost i
- 出版日期2013-6
