Graduate School, China Academy of Engineering Physics, Beijing 100193, China.
Phys Rev Lett. 2023 Mar 17;130(11):112501. doi: 10.1103/PhysRevLett.130.112501.
We consider theoretically isomeric excitation of ^{229}Th in a laser-heated cluster. A ^{229}Th cluster is first radiated by an intense femtosecond laser pulse, causing ionization of the constituting atoms. The cluster will then survive for a time on the order of 1 ps, during which the electrons collide with the nuclei repeatedly and excite them to the isomeric state. Two mechanisms are responsible for the isomeric excitation: nuclear excitation by electron capture (NEEC) and nuclear excitation by inelastic electron scattering (NEIES). By changing the laser intensity, one can tune between NEEC and NEIES continuously. This laser-heated-cluster scheme not only provides a highly efficient means for isomeric excitation, but also provides an approach for the confirmation of the NEEC process, which has been predicted for over forty years without conclusive experimental verifications.
我们从理论上考虑了激光加热团簇中^{229}Th 的同质异能激发。^{229}Th 团簇首先被强飞秒激光脉冲辐射，导致组成原子的电离。团簇随后将在 1 皮秒左右的时间内存活，在此期间，电子与原子核反复碰撞并将它们激发到同质异能态。有两种机制负责同质异能激发：电子俘获核激发（NEEC）和非弹性电子散射核激发（NEIES）。通过改变激光强度，可以连续调谐 NEEC 和 NEIES。这种激光加热团簇方案不仅为同质异能激发提供了一种高效手段，而且还为已经预测了四十多年但没有确凿实验验证的 NEEC 过程的确认提供了一种途径。
