This work provides experimental evidence of symmetry breaking in electron-impact dissociative ionization of $\mathrm{C}{\mathrm{O}}_2$. Angular correlation between the recoil direction of fragment ions and transferred momentum is measured. It reveals that despite the inversion symmetry of the $\mathrm{C}{\mathrm{O}}_2$ molecule, $\mathrm{C}{\mathrm{O}}^{+}$ is emitted preferentially in the momentum transfer direction near the thresholds of ionization to close-lying ${}^2{\mathrm{\Pi }}_{\mathrm{u}}$ and ${}^2{\mathrm{\Pi }}_{\mathrm{g}}$ states. Similar forward-backward asymmetry is found also for dissociative ionization of ${\mathrm{N}}_2$. The findings cannot be explained if ionization and dissociation are two independent steps, indicating that the Coulomb field of the slow ejected electron induces the mixing of gerade and ungerade states in the molecular ion.

中文翻译：

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线性对称分子的电子碰撞解离电离中的对称性破坏

这项工作提供了电子撞击解离电离对称性破缺的实验证据 $\mathrm{C}{\mathrm{哦}}_2$. 测量碎片离子的反冲方向与转移动量之间的角相关性。它表明，尽管反演对称$\mathrm{C}{\mathrm{哦}}_2$ 分子， $\mathrm{C}{\mathrm{哦}}^{+}$ 优先在靠近电离阈值的动量传递方向发射 ${}^2{\mathrm{\Pi }}_{\mathrm{你}}$ 和 ${}^2{\mathrm{\Pi }}_{\mathrm{G}}$状态。也发现了类似的前后不对称性对于${\mathrm{N}}_2$. 如果电离和解离是两个独立的步骤，则无法解释这些发现，这表明缓慢喷射电子的库仑场诱导了分子离子中的 gerade 和 ungerade 状态的混合。