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Experimental study of time reversal invariance and atomic final state effects in nuclear transitions
[摘要] Experiments have been performed to test time reversal invariancein nuclei using gamma transitions of oriented 191Ir and 131Xe.Thephase angle η associated with the imaginary part of the ratio of reducedmatrix elements of the gamma transition was measured through observationof the angular distribution of the linear polarization fromoriented nuclei.Interaction of the gamma ray with the atomic electroncloud can cause an additional phase shift ξ which is indistinguishable from the time-reversal phase η.Such an atomic final state effect hasbeen observed for the 129 keV transition in 191Ir. Nuclear orientationwas achieved with a large magnetic field (the hyperfine field of Ir iniron) and low temperature (20 to 30 mK obtained with a dilution refrigerator).A Compton polarimeter was used to measure linear polarizationof the E2-Ml gamma ray. The matrix-element ratio was found to have animaginary part corresponding to a phase angle (η+ξ) = (-4.8 ± 0.2) x 10-3.This measurement is in agreement with the most recent final state calculationswhich give ξ = (-4.3 ± 0.4) x 10-3. A limit |η| < 10-3 isdeduced for the time-reversal phase. In another experiment a phase angleη = (-1.2 ± 1.1) x 10-3 was measured for the E2-Ml 364 keV transition in131Xe, for which atomic final state effects are small. Both measurementsare consistent with time reversal invariance.
[发布日期]  [发布机构] University:California Institute of Technology;Department:Physics, Mathematics and Astronomy
[效力级别]  [学科分类] 
[关键词] Physics [时效性] 
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