Anomalous transmission of Mossbauer radiation in pure nuclear Laue diffraction. II. Weak absorption off resonance

Abstract

For pt.I see ibid., vol.19, no.14, p.2557 (1986). The angular dependence of the anomalous transmission of Mossbauer radiation through a perfect single-crystal platelet of ⁷FeBO₃ was studied for a pure nuclear reflection. The cases of intermediate and weak resonance absorption were realised at energy distances Delta E=+or-2 Gamma and +or-6 Gamma off resonance, where Gamma is the natural linewidth. With increasing distance Delta E an increase of the Laue-reflected peak was observed, caused by an additional contribution of the second wavefield associated with anomalously strong absorption. For the Laue transmitted beam, light-dark and dark-light intensity profiles were observed at energy distances Delta E=+2 Gamma and -2 Gamma , respectively, which are characteristic for anomalous transmission in the case of intermediate absorption. At Delta E=+or-6 Gamma , minima were observed in the Laue transmission rocking curve, which can be ascribed to an intensity transfer into the Laue reflected beam. The approximate compensation of the transmission minima by the reflection peaks is an indication of the enhancement effect, which reveals itself in pure form only at negligible resonance absorption. The combined results of parts I and II demonstrate, that in Mossbauer dynamical diffraction the different cases of strong, intermediate and weak absorption can be easily realised in one and the same crystal sample.