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arXiv · 2604.24045

Nuclear non-resonant photoexcitation assisted by electron recombination

Nan Xue·Zuoye Liu·Ziwen Li·Adriana Pálffy·Jianmin Yuan·Yuanbin Wu·Xiangjin Kong·Yu-Gang Ma
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Abstract

We investigate theoretically a nuclear excitation mechanism involving absorption of non-resonant photons leveraged by the coupling to the atomic shell. The nuclear non-resonant photoexcitation is assisted by electron recombination which compensates the energy mismatch between photon and nuclear transition energies, reminiscent of parametric up-conversion in non-linear media. This third-order process proceeds via a virtual nuclear state rather than virtual electronic states, distinguishing this mechanism from the electronic bridge. We investigate the process on the example of a so-far not observed 14.2 keV hard x-ray transition in 193Pt driven by an x-ray free-electron laser. Although the calculated cross section is small, it can be compensated by the vast number of non-resonant photons from the x-ray laser pulse. By enabling nuclear excitation through non-resonant photons, this up-conversion-like mechanism suggests new directions for non-linear x-ray interactions mediated by nuclear transitions.

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Nan Xue, Zuoye Liu, Ziwen Li, Adriana Pálffy, Jianmin Yuan, Yuanbin Wu, Xiangjin Kong, Yu-Gang Ma. 2026-04-27. Nuclear non-resonant photoexcitation assisted by electron recombination. https://doi.org/10.1007/s11433-026-2986-4

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