SDIO/1ST Ultrashort Wavelength Laser - 'Novel Experimental Schemes for Observing the Moessbauer Effect in Long-Lived Nuclear Levels and Nuclear Coherent States'.

摘要

Our results indicate that the Mossbauer Effect is occuring for the 88-keV transition of Silver 109 in silver single crystals. Furthermore, the effect appears to be an order of magnitude smaller in the horizontal geometry than in the vertical geometry. Using our model calculations, the size of the M.E. in the vertical geometry is consistent with a line broadening factor of only about 5. This would appear to be an unphysical result. These results suggest that gravitational sweeping is playing a significant role in producing an observable M.E.. Very soon we will make further model calculations incorporating the gravitational sweeping mechanism in order to evaluate its significance. In addition, we are presently performing further experiments using a thicker silver single-crystal sample which should shed light on this question. The search for the M.E. in ultra-narrow gamma-ray transitions (lifetimes on the order of seconds) is difficult. One of the methods used is based on the increased self-absorption of gamma-rays emitted in a particular direction as the temperature of the sample is lowered. This increase in absorption at low temperature is an indication of the occurrence of the M.E.. There are substantial difficulties, outlined above, associated with this technique because changes in the gamma-ray counting rates as a function of temperature are associated with a number of experimental factors other than the occurrence of the M.E.. (jhd)