Electron capture nuclear decay rate under compression in a confined environment

Abstract

We have calculated the effect of compressing the radioactive atoms in the crystal lattice environments on their electron capture nuclear decay rates. The electronic structure calculations of solids using the density functional techniques have been used to calculate the change of electron density at the nuclei and the corresponding change of electron capture nuclear decay rate of the radioactive atoms confined to the interstitial spaces of different crystal lattices. The effects of finite nuclear size and vacuum polarization were considered in the calculations. It has been found that the calculations significantly underpredict the experimentally measured increase of electron capture nuclear decay rate under compression. The increase of decay rate due to compression-induced quantum anti-Zeno effect is generally believed to be very small because of very short duration of initial nonexponential decay time for the nuclear decays. However, this effect could be observable for the electron capture nuclear decay of $$^{\mathrm {163}}$$ Ho, because of its very low decay energy. Moreover, certain models of quantum measurement indicate much longer initial nonexponential decay time and the corresponding implication on the increase of decay rate under compression is still not known. It is important to understand the large discrepancy between the measured and calculated increase of electron capture nuclear decay rate under compression and the associated role of quantum anti-Zeno effect because of their possible implications in various astrophysical and geophysical calculations.