Viscosity and ultrasonic attenuation in 4 He below 0.6 K
Department of Physics, College of Science, Korea University, Seoul 136-701, Korea
The Research Institute of Basic Science, Korea University, Seoul 136-701, Korea
Department of Physics, Seonam University, Namwon, Chunbuk 590-170, Korea
T. F. George
Office of the Chancellor / Departments of Chemistry and Physics and Astronomy,University of Wisconsin-Stevens Point, Stevens Point, Wisconsin 54481-3897, U.S.A
(Submitted November 29, 1996)
Through a treatment of three-phonon processes, the wide-angle scattering rates and the absorption rates of phonons, which characterize viscosity and ultrasonic attenuation, respectively, are calculated for 4He below 0.6K. These rates are obtained from the collision matrix which is constructed approximately from an integral eigenvalue equation for the collision operator. The sequence of the lowest eigenvalues of the collision matrix, as the angular momentum quantum number l increases, shows a saturated behavior which has not been reported before. The calculated viscosity and ultrasonic attenuation are compared with previous theoretical and experimental results.