Unexpected increase of Be-7 decay rate under compression

摘要

It is important to understand the effect of compression on the decay rate of Be-7 because of its significance in calculating Be-7 decay rate at the solar core and corresponding B-8 neutrino flux. We have measured that the decay rate of Be-7 is faster in the smaller spatial confinement of Pd lattice compared to the larger spatial confinement of Pb lattice by (0.82 +/- 0.16)%, indicating the effect of compression on the decay rate of Be-7 ion, because low and similar electron affinities of Pd and Pb cannot produce any observable effect. Similar results were observed earlier by applying high external pressure on (BeO)-Be-7 lattice. The density functional calculations underpredict the increase of Be-7 decay rate under compression by a large factor, although they can account for the effect of electron affinity reasonably well. The unexpectedly large increase (similar to 1%) of Be-7 decay rate under compression (25-40 GPa) compared to the state-of-the-art calculations could have implications on the calculated Be-7 decay rate at the solar core.