Excitation of atomic nuclei in hot plasma through resonance inverse electron bridge

Abstract

A process of nucleus excitation by photons under the mechanism of the inverse electron bridge (IEB) is examined provided the energies of atomic and nuclear transitions coincide. It is shown that in this case, the excitation of nuclei with $EL$ $[ML]$ transition with the energy ${\ensuremath{\omega}}_{N}\ensuremath{\lesssim}10\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ is strengthened relative to the process of photoabsorption by nucleus by a factor of $1/{({\ensuremath{\omega}}_{N}{r}_{0})}^{2(L+2)}$ $[{e}^{4}/{({\ensuremath{\omega}}_{N}{r}_{0})}^{2(L+2)}]$, where ${r}_{0}$ is a typical size of domain in the ion shell for accumulation of electronic integrals. In the $^{84}\mathrm{Rb}$ nuclei the IEB cross section for the 3.4 keV $M1$ transition ${6}^{\ensuremath{-}}$(463.59 keV) $\ensuremath{\leftrightarrow}{5}^{\ensuremath{-}}(463.59\phantom{\rule{0.16em}{0ex}}\mathrm{keV})$ can exceed even a photoexcitation cross section for the $3.4\phantom{\rule{0.16em}{0ex}}\mathrm{keV}\phantom{\rule{0.16em}{0ex}}E1$ transition with the reduced probability in the Weisskopf model ${B}_{W.u.}(E1)=1$. This result can be important for understanding the mechanisms of atomic nucleus excitation in hot plasma. In particular, the considered process is capable to provide the existence of so called gamma luminescence wave or a nuclear isomer ``burning'' wave---an analog of self-maintaining process of triggered depopulation of nuclear isomer.