X-RAY DETERMINATION OF THE ELASTIC-DEFORMATION OF A PERFECT CRYSTAL NEUTRON INTERFEROMETER - IMPLICATIONS FOR GRAVITATIONAL PHASE-SHIFT EXPERIMENTS

The quantum mechanical phase shift for a massive particle due to gravi ty has been observed in a series of neutron interferometry experiments using perfect crystal silicon interferometers. While the results of t hese measurements are in qualitative agreement with the predictions of non-relativistic quantum mechanics and Newtonian gravity, there remai ns a very significant discrepancy between theory and experiment. It ha s been suggested that this discrepancy is due to a systematic effect r elated to the elastic deformation of the monolithic interferometer. In this work we describe X-ray measurements which indicate that such a s ystematic effect was overlooked in previous measurements. We conclude that the magnitude of these effects is sufficiently large to account f or the current discrepancy between theory and experiment.