Test of time reversal invariance in Fe-57
Test of time reversal invariance in Fe-57
复制标题
Fe-57 时间反转不变性测试
DOI：
10.1103/physrevc.16.2381
复制
发表时间：
1977
期刊：
影响因子：
--
通讯作者：
H. Henrikson
中科院分区：
文献类型：
--
作者：
N. Cheung;F. Boehm;H. Henrikson
An experiment has been performed to test time reversal invariance by observing the angular distribution of the linear polarization of the mixed $E2$ and $M1$ 122 keV $\ensuremath{\gamma}$ rays in $^{57}\mathrm{Fe}$ emitted from oriented $^{57}\mathrm{Co}$ nuclei. Nuclear orientation was achieved with a high magnetic field (the 288 kG hyperfine field of $^{57}\mathrm{Co}$ in an iron lattice) and a low temperature (16.5 to 18 mK obtained with a $^{3}\mathrm{He}$-$^{4}\mathrm{He}$ dilution refrigerator). If time reversal invariance is violated, a term in the angular distribution of the form $(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\times\else\texttimes\fi{}\stackrel{\ensuremath{\rightarrow}}{E})(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{E})sin\ensuremath{\eta}$ would be present, where the vectors $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ and $\stackrel{\ensuremath{\rightarrow}}{E}$ describe the propagation and linear polarization of the $\ensuremath{\gamma}$ ray, respectively, and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ is the nuclear orientation vector. The quantity $\ensuremath{\eta}$ is the phase angle between the $E2$ and $M1$ matrix elements of the $\ensuremath{\gamma}$ transition. In our experiment the linear polarization was measured with a Compton polarimeter using an aluminum scatterer and NaI(Tl) detectors. From the observed asymmetry of $A=(\ensuremath{-}0.35\ifmmode\pm\else\textpm\fi{}0.78)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, a value of $sin\ensuremath{\eta}=(\ensuremath{-}3.1\ifmmode\pm\else\textpm\fi{}6.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ was obtained. This result is consistent with time reversal invariance. Possible small contributions to the phase angle from atomic and nuclear final state effects are discussed.
An experiment has been performed to test time reversal invariance by observing the angular distribution of the linear polarization of the mixed $E2$ and $M1$ 122 keV $\ensuremath{\gamma}$ rays in $^{57}\mathrm{Fe}$ emitted from oriented $^{57}\mathrm{Co}$ nuclei. Nuclear orientation was achieved with a high magnetic field (the 288 kG hyperfine field of $^{57}\mathrm{Co}$ in an iron lattice) and a low temperature (16.5 to 18 mK obtained with a $^{3}\mathrm{He}$-$^{4}\mathrm{He}$ dilution refrigerator). If time reversal invariance is violated, a term in the angular distribution of the form $(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\times\else\texttimes\fi{}\stackrel{\ensuremath{\rightarrow}}{E})(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})(\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{E})sin\ensuremath{\eta}$ would be present, where the vectors $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ and $\stackrel{\ensuremath{\rightarrow}}{E}$ describe the propagation and linear polarization of the $\ensuremath{\gamma}$ ray, respectively, and $\stackrel{\ensuremath{\rightarrow}}{\mathrm{J}}$ is the nuclear orientation vector. The quantity $\ensuremath{\eta}$ is the phase angle between the $E2$ and $M1$ matrix elements of the $\ensuremath{\gamma}$ transition. In our experiment the linear polarization was measured with a Compton polarimeter using an aluminum scatterer and NaI(Tl) detectors. From the observed asymmetry of $A=(\ensuremath{-}0.35\ifmmode\pm\else\textpm\fi{}0.78)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, a value of $sin\ensuremath{\eta}=(\ensuremath{-}3.1\ifmmode\pm\else\textpm\fi{}6.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ was obtained. This result is consistent with time reversal invariance. Possible small contributions to the phase angle from atomic and nuclear final state effects are discussed.