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Cross‐relaxation of nuclear spins at low temperatures
Author(s) -
Buishvili L. L.,
Foki. P.,
Chelidze L. T.
Publication year - 1986
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221330114
Subject(s) - spins , zeeman effect , dipole , relaxation (psychology) , condensed matter physics , physics , atomic physics , zeeman energy , chemistry , quantum mechanics , magnetic field , psychology , social psychology
A system of equations is derived for the evolution under action of cross‐relaxation (CR) of the dipole–dipole reservoir (DDR) and Zeeman subsystems, redefined taking into account the fact, that the part of secular dipole‐dipole interaction H ′ d , which causes homogeneous displacement of spin resonant frequencies at low temperatures (LT) must be subtracted from H ′ d . The case is considered, when the influence of the change of LT displacement due to CR on the energy, absorbed by DDR, is stronger, than that of the usual high‐temperature term. It is shown, that in this situation both, DDR and spins under CR acquire a negative temperature in spite of the fact, that the frequency of saturated spins is smaller than the frequency of spins under CR. This behaviour differs from the high‐temperature result.