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Articles 61 - 64 of 64
Full-Text Articles in Physics
Theory Of Motional Inhibition Of Interlayer Quantum Tunneling In Thin He-3 Films, Wj Mullin, A Landesman
Theory Of Motional Inhibition Of Interlayer Quantum Tunneling In Thin He-3 Films, Wj Mullin, A Landesman
William J. Mullin
An attempt is made to interpret NMR data on 3He films for coverages just over one monolayer in terms of motion due to the quantum exchange of particles between layers. A summary of the relevant data and of various possible relaxation mechanisms is given and it is found that a portion of the data seems amenable to an interlayer exchange interpretation. The detailed theory of this process requires the use of the exchange operator concept and a Kubo-theory treatment of the effect of second-layer motion on the exchange process. It is shown that the ldquobarerdquo interlayer exchange process characterized by …
New Evidence For Zero-Temperature Relaxation In A Spin-Polarized Fermi Liquid, H Akimoto, D Candela, Js Xia, Wj Mullin, Ed Adams, Ns Sullivan
New Evidence For Zero-Temperature Relaxation In A Spin-Polarized Fermi Liquid, H Akimoto, D Candela, Js Xia, Wj Mullin, Ed Adams, Ns Sullivan
William J. Mullin
Spin-echo experiments are reported for 3He-4He solutions under extremely high B/T conditions, B=14.75 T and T≥1.73 mK. The 3He concentration x3 was adjusted close to the value xc≈3.8% at which the spin-rotation parameter μM0 vanishes. In this way the transverse and longitudinal spin-diffusion coefficients D⊥,D∥ were measured while keeping |μM0|<1. It is found that the temperature dependence of D⊥ deviates strongly from 1/T2, with anisotropy temperature Ta=4.26-0.44+0.18 mK. This value is close to the theoretical prediction for dilute solutions and suggests that spin current relaxation remains finite as the temperature tends to zero.
The Loop-Gas Approach To Bose-Einstein Condensation For Trapped Particles, Wj Mullin
The Loop-Gas Approach To Bose-Einstein Condensation For Trapped Particles, Wj Mullin
William J. Mullin
We examine Bose–Einstein condensation (BEC) for particles trapped in a harmonic potential by considering it as a transition in the length of permutation cycles that arise from wave-function symmetry. This “loop-gas” approach was originally developed by Feynman in his path-integral study of BEC for a homogeneous gas in a box. For the harmonic oscillator potential it is possible to treat the ideal gas exactly so that one can easily see how standard approximations become more accurate in the thermodynamic limit (TDL). One clearly sees that the condensate is made up of very long permutation loops whose length fluctuates ever more …
Viscosity Increase Upon Spin Polarization Of A Dilute Fermi Gas, D Candela, Lj Wei, Dr Mcallaster, Wj Mullin
Viscosity Increase Upon Spin Polarization Of A Dilute Fermi Gas, D Candela, Lj Wei, Dr Mcallaster, Wj Mullin
William J. Mullin
A vibrating-wire technique has been used to directly measure the viscosity increase in a dilute 3-4He solution caused by brute-force spin polarization up to 40%. The viscosity of a solution with degeneracy temperature TF=19.5 mK was measured over the temperature range 6.1–100 mK in magnetic fields of 1.00 and 7.96 T. Spin polarization caused a marked decrease in the mechanical Q of the viscometer at low temperatures. The observed viscosity is compared with calculations of the transport coefficients of dilute quantum gases for all temperatures and spin polarizations.