Relaxation and deorientation of110Ag(T
1/2=24.4s) nuclei produced by capture of polarized neutrons in the silver halides |
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Authors: | J Mertens H Ackermann D Dubbers P Heitjans A Winnacker P von Blanckenhagen |
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Institution: | 1. I. Physikalisches Institut der Universit?t Heidelberg, Germany 3. Institut für Angewandte Kernphysik, Kernforschungszentrum Karlsruhe, Germany
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Abstract: | Polarized110Ag nuclei are produced in the silver halides by capture of polarized neutrons at temperatures below 30 K and magnetic field strengths up to 6 kOe. The depolarization process is studied by observation of the β decay asymmetry as a function of magnetic field, temperature and of the radio frequency field strength in NMR signals. The depolarization is caused by a field dependent deorientation process and by temperature dependent spin-lattice relaxation. The deorientation is due to a succession of coupling steps of the nuclear spin with electromagnetic fields of defects generated as a consequence of the capture process, and the field dependence of the polarization can be understood as a decoupling curve. The temperature dependence of the spin-lattice relaxation is in accordance with the theory of quadrupolar relaxation above 18 K if an empirical phonon spectrum is used for the calculation. At lower temperatures the experimental relaxation rate is anomalously high, which may be due to resonance modes connected with recoil lattice defects. |
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