The hydrogen anomaly in neutron Compton scattering: new experiments and a quantitative theoretical explanation

摘要

No consensus has been reached so far about the hydrogen anomaly problem in Compton scattering of neutrons, although strongly reduced H cross-sections were first reported almost 20 years ago. Over the years, this phenomenon has been observed in many different hydrogen-containing materials. Here, we use yttrium hydrides as test objects, YH2, YH3, YD2 and YD3, Y(HxD1-x)(2) and Y(HxD1-x)(3), for which we observe H anomalies increasing with transferred momentum q. We also observe reduced deuteron cross-sections in YD2 and YD3 and have followed those up to scattering angles of 140 degrees corresponding to high momentum transfers. In addition to data taken using the standard Au-197 foils for neutron energy selection, the present work includes experiments with Rh-103 foils and comparisons were also made with data from different detector setups.