电子碰撞导致He原子电离激发过程的(e, γ2e)三重符合测量

电子碰撞导致的He原子电离伴随激发过程是最基本的量子力学四体问题之一。已有的实验集中在采用(e, 2e)方法测量末态两个出射电子，通过反应的Q值确定末态He+*离子所处的主量子数。如果能够在探测末态电子的同时符合探测处于He+(2p)激发态的离子向1s跃迁所辐射的光子，即(e, γ2e)实验，将能够在确定主量子数n的同时精确选择角动量量子数l。受电离激发截面低、光探测效率低、接收立体角小等因素制约，(e, γ2e)探测是非常具有挑战性的实验。本申请拟基于反应谱仪技术实现对He原子电离激发过程的(e, γ2e)三重符合探测，并提高符合计数效率，实验测得主量子数及角动量量子数精确确定的全微分截面信息。通过这些微分截面信息我们将研究角动量量子数对动力学机制的影响，同时也将为已有的各种理论计算模型提供最严格的检验。

Electron induced excitation-ionization of helium is one of the most fundamental four-body problem. Most of experiments on this process employ the so called (e, 2e) methods, and only determine the principle quantum number n, while leaving the angular momentum quantum number l of the He+ ion in the excited state unseparated. The He+(2p) may decay to 1s by emitting a fluorescence photon. If this photon is detected in coincidence with the two outgoing electrons, i.e. the so called (e, γ2e) experiment, the angular momentum quantum number l is then determined. Such an experiment is extremely challenging due to the low cross for excitation-ionization and the limited efficiency for photon detection. In the present application, we aim to achieve the (e, γ2e) measurement, and deduce the quantum numbers n and l definitely determined fully differential cross sections for excitation-ionization to He+(2p). Such information will offer the most stringent test for various theoretical models and at the same time enhance our understanding of excitation-ionization dynamics.