由束流感生回流电流驱动的主导性电子俘获核激发
Predominant Nuclear Excitation by Electron Capture Driven by Beam-Induced Return Currents
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中文总结 AI 辅助
本文提出利用束流感生回流电流构建共振电子源，可高效产生占比97.68%的电子俘获核激发（NEEC）事件，为固体中可控共振核激发提供新途径。
中文摘要 AI 辅助
电子俘获核激发（NEEC）早在近五十年前就被预言，但由于其微弱的共振信号被竞争性的电子驱动激发通道掩盖，至今仍未在实验中观测到。本文表明，束流感生的表面回流电流可自然克服这一限制，为固体密度229Th的8.36 eV核跃迁构建出自组织的共振电子源。相对论电子束沿固体表面驱动局域化回流电流，该电流通过碰撞电离同时产生俘获空位，并通过漂移费米分布为NEEC提供共振电子；回流电流与驱动束流的空间分离以及泡利不相容原理，可强烈抑制非弹性电子散射引发的竞争性核激发。在实验可行参数下，本文预测产生2.40×10^5次NEEC事件，NEEC占比达97.68%，且激发产额可在保持NEEC主导地位的同时，调谐数个数量级。这些结果确立了束流感生回流电流作为固体中可控共振核激发的途径，为研究电子驱动核过程开辟了新方向。
英文摘要
Predicted nearly five decades ago, nuclear excitation by electron capture (NEEC) remains experimentally elusive because its weak resonant signal is obscured by competing electron-driven excitation channels. Here we show that beam-induced surface return currents naturally overcome this limitation by creating a self-organized resonant electron source for the 8.36-eV nuclear transition in solid-density 229Th. A relativistic electron beam drives localized return currents along the solid surface, which simultaneously generate capture vacancies through impact ionization and provide resonant electrons for NEEC via a drifted Fermi distribution. Their spatial separation from the driving beam and the Pauli exclusion principle strongly suppress competing nuclear excitation by inelastic electron scattering. For experimentally available parameters, we predict 2.40*10^5 NEEC events with a NEEC fraction of 97.68%, and show that the excitation yield can be tuned over several orders of magnitude while preserving NEEC dominance. These results establish beam-induced return currents as a controllable route to resonant nuclear excitation in solids and open a new avenue for studying electron-driven nuclear processes.
