Dipole-dipole Reservoir Research Articles

Saturation of a spin system with a nonequidistant spectrum in a solid

The saturation of a nonequidistant spin system is analyzed for the example of spin-5/2 nuclear quadrupole resonance in a molecular crystal; nonequilibrium states of the dipole-dipole reservoir are taken into account. The Zubarev method of a nonequilibrium statistical operator is used to derive equations generalizing the phenomenological balance equations for the populations in the case of a solid with strong magnetic dipole-dipole interactions. The real and imaginary parts of the dynamic susceptibility of the system, χ'-iχ, are found.

The Influence of the Dipole-Dipole Interactions on the Phonon Induction

Abstract It is shown that the none quilibrium state of the dipole-dipole reservoir in paramagnetic and paraelectric systems can stimulate the generation of the coherent spontaneous radiation essentially. At the same time the uncoherent spontaneous radiation and coherent induced (in the Einstein sense) radiation canN′t be amplified in this conditions essentially. Moreover the electromagnetic and acoustic maser-effects and uncoherent apontaneous radiation completely disappear in the limit case of enough small absolute values of the dipole-dipole system (DDS) temperature. The nuclear polarization is also absent at enough low absolute electron-nuclear and nuclear-nuclear DDS temperatures. All of these consequences follow from the obvious trace property of the product of n-particle density matrix operators and operators of observable quantities constituted from m-particle operators: this trace is identically equal to zero if m > n (all n or m particles are different).

Proton polarization and relaxation in dilute paramagnetic crystals by rotational cooling: II. Yttrium chloride hexahydrate doped with Yb ions

A rotational-cooling method is employed to obtain proton polarization in crystals of YCl 3·6H 2O doped with Yb 3+ ions. The relaxation behaviour of the protons is investigated as a function of magnetic field H (1 kOe ≲ H ≲ 10 kOe), temperature T (0.05 K ≲ T ≲ 1 K) and concentration c of the rare-earth ions (0.05%≲ c ≲ 1.4%). For concentrations of the Yb ions in the range 0.3 ≲ c ≲ 1.4% the relaxation times are strongly influenced by the dipole-dipole reservoir of the electron spins. The electron-spin-lattice relaxation rate is calculated on the basis of the proton-spin-lattice relaxation rates ( T -1 1n at the lower Yb concentrations. Because the T 1n measurements are reasonally well described by a hexagonal crystal-field interaction on the Yb ions, a hexagonal crystal-field hamiltonian is proposed. Polarization measurements give g min = 0.08 ± 0.01.

Proton polarization and relaxation in dilute paramagnetic crystals by rotational cooling I. yttrium ethyl sulfate doped with Yb and Dy ions

The method of proton polarization by means of rotational cooling is employed in crystals of Y (C 2H 5SO 4) 3 · 9H 2O doped with Yb 3+ and Dy 3+ ions. The decay of the proton polarization is observed as a function of magnetic field H(1 kOe≲ H ≲ 10 kOe), temperature T (0.05 K ≲ T ≲ 1 K) and concentration of the rare-earth ions c(0.07% ≲ c ≲ 3%). For an explanation of the results on proton spin-lattice relaxation times the inclusion of the dipole-dipole reservoir (D.D.R.) of the paramagnetic ions is required. The influence of the concentration of the Yb or Dy ions on the maximum obtainable proton polarization is discussed. The electron spin-lattice relaxation appears to be mainly determined by the direct process.