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'Low Temperatures' in keywords Facet   Publication Year 1990  [X]
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1990[X]
1Author    Mariusz Máckowiak, Costas DimitropoulosRequires cookie*
 Title    Calculation of NQR v's and T l s being proportional to T 4 and T 5 , respectively  
 Abstract    The second-order Raman phonon process for a multilevel spin system is shown to give a quadru-polar spin-lattice relaxation rate T x ~ varying as T 5 at very low temperatures. This relaxation rate for quadrupole spins is similar to the one discussed for a paramagnetic spin system having a multilevel ground state. The temperature dependence of Tj is discussed on the basis of some simplifying assumptions about the nature of the lattice vibrations in the Debye approximation. This type of relaxation process has been observed below 20 K in tetramethylammonium hydrogen bis-trichloroacetate for the 35 C1 Ti _1 . Below 20 K the NQR frequency in the same crystal reveals a T 4 temperature dependence due to the induced modulations of the vibrational and librational coordinates by the low-frequency acoustic phonons. 
  Reference    Z. Naturforsch. 45a, 536—540 (1990); received August 22 1989 in revised form November 24 1989 
  Published    1990 
  Keywords    Quadrupole relaxation, low temperature, NQR 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0536.pdf 
 Identifier    ZNA-1990-45a-0536 
 Volume    45