The electrical strength of a molecule is a measure of its ability to act as an insulator and to absorb electrons. SF₆ is a high electric strength gas. This work tries to explain why molecules like SF₆ have a high electrical strength from the perspective of electron molecule scattering. The presence of a very low energy (<<1 eV) totally symmetric state in form of a very low-lying resonance, virtual state or very weakly bound state appears to be crucial. R-matrix calculations performed at the static exchange plus polarisation (SEP) level are performed for a number of molecules that show a range of electrical strengths. SEP calculations suggest that SF₆ has a strong low energy ²A _g resonance feature which becomes a weakly bound state as more virtual orbitals are included in the calculation. High electrical strength molecules such as CCl₄, CCl₃F and CCl₂F₂ also have a totally-symmetric low-energy resonance, while the low electrical strength molecules such as CH₄, CH₃F…CF₄ and CClF₃, do not show any resonance behaviour in the low energy region. It is suggested that this low energy feature can be used as an indicator when searching for new molecules with high electrical strength facilitating searches for new gases which could provide an alternative to SF₆.

分子的电强度是其充当绝缘体和吸收电子的能力的量度。SF ₆是高电强度气体。这项工作试图从电子分子散射的角度解释为什么像SF ₆这样的分子具有高电强度。以非常低的共振，虚拟状态或非常弱的束缚状态形式存在非常低的能量（<< 1 eV）完全对称状态似乎至关重要。在静态交换加极化（SEP）级别上执行的R矩阵计算是针对显示一定电气强度范围的许多分子执行的。SEP计算表明，SF ₆具有很强的低能量² A _g 共振特征随着计算中包含更多的虚拟轨道而变为弱束缚状态。高电强度的分子（例如CCl ₄，CCl ₃ F和CCl ₂ F _2）也具有完全对称的低能共振，而低电强度的分子（例如CH ₄，CH ₃ F…CF ₄和CClF ₃）却具有在低能量区域没有任何共振行为。建议在寻找具有高电强度的新分子时，可以将此低能量特征用作指示剂，以利于寻找可以提供SF ₆替代品的新气体。