Problem of parity nonconservation inFe57andSn119nuclei

We consider parity nonconservation effect for the Mossbauer transitions in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ and ${}_{}{}^{119}{}_{}{}^{}\mathrm{Sn}$ nuclei. To simplify the calculations we use contact approximation for nucleon-nucleon weak interaction. A corresponding parity nonconserving effective Hamiltonian is presented. The result of the calculation of γ-quantum circular polarization degree P∼3×${10}^{\mathrm{-}8}$ strongly contradicts the experimental value P∼${10}^{\mathrm{-}3}$. One may consider this huge disagreement as an indication of the unknown nuclear phenomena which leads to the enhancement of parity nonconservation. We stress the importance of a new independent measurement of the effect.