Abstract

Atoms subjected to extreme environmental conditions are of fundamental importance due to the modification of their electronic properties. In this work, we study the helium atom when immersed in a plasma environment. In order to describe the plasma medium, we use two models when solving the Schrödinger equation in a restricted Hartree–Fock approach: the Debye–Hückel screened (DHS) potential and a more general exponential-cosine screened Coulomb (ECSC) potential. The plasma length parameter, \(\lambda \), in both model potentials characterizes the plasma screening effects which cause an increase or decrease in the electronic properties of the helium atom. We report results for the total electronic ground state energy, orbital energy, dipole oscillator strengths, generalized oscillator strengths (GOS), mean excitation energy, electrostatic dipole polarizability, and electronic stopping cross section. We find that the ECSC plasma model produces a less bound system than the DHS plasma model at the same value of the screening length, \(\lambda \). However, the ECSC model potential has a stronger dipole transition from the 1s to the 2p and 3p states than the DHS model potential. Also, the ECSC potential predicts a higher static dipole polarizability than the DHS model potential, with a consequent lower mean excitation energy. We also find a larger GOS for the ECSC than for the DHS for the same momentum transfer at the same value of the screening length, \(\lambda \). Consequently, the ECSC mode potential produces a larger electronic stopping cross section than the DHS for the same \(\lambda \) and projectile velocity. In the limit of \(\lambda \rightarrow \infty \), we have excellent agreement with the free helium properties. These quantitative values for the electronic properties would be useful for the investigations of the atomic structure and collisions of helium atoms immersed in plasmas.

Graphic Abstract

中文翻译：

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偶极子和广义振荡器强度相关的浸在等离子体中的氦原子的电子性质

摘要

由于其电子特性的改变，处于极端环境条件下的原子至关重要。在这项工作中，我们研究了浸入等离子体环境中的氦原子。为了描述等离子体介质，在受限的Hartree-Fock方法中求解Schrödinger方程时，我们使用两个模型：Debye-Hückel筛选（DHS）势和更通用的指数余弦筛选Coulomb（ECSC）势。等离子长度参数\（\ lambda \），在两个模型中，电势都表征了等离子体筛选效应，该效应导致氦原子电子特性的增加或减少。我们报告了总电子基态能量，轨道能量，偶极子振荡器强度，广义振荡器强度（GOS），平均激发能，静电偶极子极化率和电子停止截面的结果。我们发现，在相同的筛选长度值\（\ lambda \）下，ECSC血浆模型比DHS血浆模型产生的结合更少。但是，ECSC模型的电势具有从1 s到2 p和3 p的更强的偶极跃迁比DHS模型的潜力更大。而且，ECSC电位比DHS模型电位预测到更高的静态偶极极化率，因此平均激发能量更低。对于相同的动量传递，在相同的屏蔽长度\（\ lambda \）的情况下，对于ECSC，我们还发现，与DHS相比，ECSC的GOS更大。因此，对于相同的λ和射弹速度，ECSC模式电势比DHS产生更大的电子停止横截面。在\（\ lambda \ rightarrow \ infty \）的范围内，我们与自由氦气性质具有极好的一致性。这些电子性能的定量值将有助于研究原子结构和浸入等离子体中的氦原子的碰撞。

图形摘要