A study of asymmetries in gamma scattering by Fe-57



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In simple 90[degree] scattering of 14.4 KeV gamma-rays from Fe-57, we have observed several per cent difference in the intensities of the conjugate lines in the six-line spectrum depending on the vectorial relations between the wave vectors for the incident gamma-rays K[lowered i] , the out going wave vectors, K[lowered f] , and the internal magnetic induction field B. The intensity of the line corresponding to the m=1/2 -> 3/2 -> 1/2 transition differs from that of the conjugate transition m=-1/2 -> -3/2 -> —1/2 , by 6.8 %. Intensity differences are also found between the m= 1/2 -> -1/2 -> (1/2 , - 1/2) line and its conjugate transition line. The sign of this asymmetry depends on the sign of K[lowered i] x K[lowered f] [dot] B. No asymmetry is expected if the 14.4 KeV Mossbauer scattering is considered purely as a two-step process, namely resonance absorption followed by re-emission. It is likely that this asymmetry is the interference between electronic (Thomson) scattering and nuclear resonant scattering as suggested by P. Debrunner. A theory, which agrees closely with this observed asymmetry in sign as well as in magnitude, is established.