Efficient production of the nuclear isomer Mo93m with laser-accelerated proton beam and its astrophysical implication on Mo92

Nuclear isomers play a key role in the creation of the elements in the universe and potentially have significant applications related to the controlled release of nuclear energy on demand. Particularly, $^{93m}\mathrm{Mo}$ is a good candidate for studying the depletion of nuclear isomers via nuclear excitation by electron capture. Therefore, it is necessary to explore the efficient approach of $^{93m}\mathrm{Mo}$ production. In this paper, we experimentally demonstrate an efficient production of $^{93m}\mathrm{Mo}$ via $^{93}\mathrm{Nb}(p,n)$ reaction induced by an intense laser pulse. Employing the picosecond-duration, 100 J laser pulse, the $^{93m}\mathrm{Mo}$ isomer at 2425 keV ($21/{2}^{+}$, ${T}_{1/2}=6.85\phantom{\rule{0.16em}{0ex}}\mathrm{h}$) is generated with a high yield of $1.8\ifmmode\times\else\texttimes\fi{}{10}^{6}$ particles/shot. The resulting peak production efficiency reaches ${10}^{17}$ particles/s, which is at least five orders of magnitude higher than that obtained using the classical accelerator. The impacts of the production and destruction of $^{93m}\mathrm{Mo}$ to the astrophysical $p$-nuclide $^{92}\mathrm{Mo}$ are studied. It is found that the $^{93}\mathrm{Nb}(p,n)\phantom{\rule{0.16em}{0ex}}^{93m}\mathrm{Mo}$ reaction is an important production path of $^{93m}\mathrm{Mo}$, which could further influence the production of $^{92}\mathrm{Mo}$. In addition, a direct measurement of the $(p,n)$ reaction rate is proposed using the laser-induced proton beam of which the energies follow the Maxwell-Boltzmann distribution well. It is believed that the laser-induced proton beam opens an avenue for the production of nuclear isomers with high peak efficiency used for the studies of $p$-nuclei nucleosynthesis.