铕原子4f76pns系列自电离态的光谱和动力学过程

通过共振激发技术和速度影像法对铕原子4f⁷6pns（n=7，8）自电离态进行了系统性的研究。首先采用三步共振激发技术探测光谱，通过前两步固定波长的激光将铕原子激发到4f⁷6p²态上后扫描第三步激光的波长，使得三步激光的能量总和位于铕原子4f⁷6pns（n=7，8）自电离态能域附近，从而得到该自电离态的光谱；然后采用速度影像法对其动力学过程进行探测，经过数据分析得到铕原子4f⁷6pns（n=7，8）自电离态的衰变分支比和弹射电子的角分布。不仅从光谱中观察到了强烈的组态相互作用并且确定了部分能态的总角动量，从自电离弹射电子角分布中观察到铕原子4f⁷6pns（n=7，8）自电离态复杂的物理机制，还在该能域内观测到了粒子数反转。最后，本文还对孤立实激发技术在探测低n值自电离态光谱的适用性进行了讨论。

Spectra and Dynamic Properties of Eu 4f76pns Autoionizing States

The spectra and dynamic properties of Eu 4f⁷6pns(n=7, 8) autoionizing states are studied systematically with the resonance-ionization spectroscopy(RIS) and the velocity-map imaging(VMI) techniques. The RIS technique is utilized to obtain the spectra of Eu 4f⁷6pns(n=7, 8) autoionizing states with the three-step excitation:the wavelengths of the first two-step lasers are fixed, while that of the last-step laser is scanned around the region of the 4f⁷6pns(n=7, 8) autoionizing states. The VMI technique is used to detect the dynamic process of autoionization, from which the branching ratio(BR) of ions and the angular distribution(AD) of ejected electrons from Eu 4f⁷6p7s autoionizing states are achieved. The heavy configuration interaction is observed in the spectra of Eu 4f⁷6pns(n=7,8) autoionizing states, measured with RIS spectroscopy technique. The present study reveals the profound variations of AD and BR with energy in the region of the 4f⁷6p7s autoionization resonance, highlighting the complicated nature of the autoionization process for the lowest member of Eu 4f⁷6pns autoionization series. Population inversion is observed by analysis of the BR, while the validity of the well-known isolated core excitation(ICE) technique used for obtaining autoionization spectrum is discussed.