Time Reversal Test inFe57

The linear polarization of the $E2-M1\mathrm{}$ 122-keV $\gamma$ ray of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ following the electron capture decay of polarized ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ was measured with a Compton polarimeter. An average time-reversal-noninvariant counting asymmetry of (-0.4 ± 0.8) × ${10}^{-5\mathrm{}}$ was obtained. This corresponds to a phase angle between the $E2\mathrm{}$ and $M1\mathrm{}$ matrix elements of $sin\eta =(-3.1\mathrm{}\pm 6.5)\times {10}^{-4\mathrm{}}$, consistent with time-reversal invariance.