Creation of high-energy phonons by four-phonon processes in anisotropic phonon systems of He II

Автор(и)

  • I.N. Adamenko Karazin Kharkov National University, 4, Svobody Sq., Kharkov 61077, Ukraine
  • Yu.A. Kitsenko Akhiezer Institute for Theoretical Physics National Science Center "Kharkov In stitute of Physics and Technology" National Academy of Sciences of Ukraine 1 Academicheskaya Str., Kharkov 61108, Ukraine
  • K.E. Nemchenko Karazin Kharkov National University, 4, Svobody Sq., Kharkov 61077, Ukraine
  • V.A. Slipko Karazin Kharkov National University, 4, Svobody Sq., Kharkov 61077, Ukraine
  • A.F.G. Wyatt School of Physics, University of Exeter, Exeter EX4 4QL, UK

DOI:

https://doi.org/10.1063/1.2737546

Ключові слова:

phonon–phonon interaction, liquid helium, anisotropic phonon system.

Анотація

The problem of the creation of high-energy phonons (h-phonons) by a pulse of low-energy phonons (l-phonons) moving from a heater to a detector in superfluid helium, is solved. The rate of h-phonon creation is obtained and it is shown that created h-phonons occupy a much smaller solid angle in momentum space, than the l-phonons. An analytical expression for the creation rate of h-phonon, along the symmetry axis of a pulse, are de rived. It al lows us to get useful approximate analytical expressions for the creation rate of h-phonons. The time dependences of the parameters which de scribe the l-phonon pulse are obtained. This shows that half of the initial energy of l-phonon pulse can be transferred into h-phonons. The results of the calculations are com pared with experimental data and we show that this theory explains a number of experimental results. The value of the momentum, which separates the l- and h-phonon subsystems, is found.

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Опубліковано

2007-03-26

Як цитувати

(1)
Adamenko, I.; Kitsenko, Y.; Nemchenko, K.; Slipko, V.; Wyatt, A. Creation of High-Energy Phonons by Four-Phonon Processes in Anisotropic Phonon Systems of He II. Fiz. Nyzk. Temp. 2007, 33, 523-537.

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