The possibility for helium-induced electronic transitions in a photo-excited atom is investigated using Ba⁺ excited to the 6p ²P state as a prototypical example. A diabatization scheme has been designed to obtain the necessary potential energy surfaces and couplings for complexes of Ba⁺ with an arbitrary number of helium atoms. It involves computing new He–Ba⁺ electronic wave functions and expanding them in determinants of the non-interacting complex. The 6p ²P ← 6s ²S photodissociation spectrum of He⋯Ba⁺ calculated with this model shows very weak coupling for a single He atom. However, several electronic relaxation mechanisms are identified, which could potentially explain the expulsion of barium ions from helium nanodroplets observed experimentally upon Ba⁺ photoexcitation. For instance, an avoided crossing in the ring-shaped He₇Ba⁺ structure is shown to provide an efficient pathway for fine structure relaxation. Symmetry breaking by either helium density fluctuations or vibrations can also induce efficient relaxation in these systems, e.g., bending vibrations in the linear He₂Ba⁺ excimer. The identified relaxation mechanisms can provide insight into helium-induced non-adiabatic transitions observed in other systems.

中文翻译：

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氦诱导的光激发Ba + -Hen激基复合物的电子跃迁

以Ba ⁺激发至6p ² P态为例，研究了光激发原子中氦诱导电子跃迁的可能性。已经设计了一种绝热方案，以获取必要的势能表面和Ba ⁺与任意数量的氦原子的配合物的耦合。它涉及计算新的He-Ba ⁺电子波函数，并在非相互作用复合物的决定因素中扩展它们。He⋯Ba ⁺的6p ² P←6s ² S光解离光谱用此模型计算得出的结果表明，单个He原子的耦合非常弱。然而，确定了几种电子弛豫机制，这可能解释了钡⁺光激发实验观察到的钡离子从氦纳米液滴中的排出。例如，显示出避免在He ₇ Ba ⁺环形结构中交叉，为精细结构松弛提供了有效途径。氦气密度波动或振动引起的对称性破坏也会在这些系统中引起有效的弛豫，例如线性He ₂ Ba ⁺中的弯曲振动准分子。所确定的弛豫机制可以洞察其他系统中观察到的氦诱导的非绝热转变。