We calculate elastic and positronium (Ps) breakup cross sections for collisions of Ps with ${\mathrm{O}}_2$ and ${\mathrm{CO}}_2$ molecules in the fixed-nuclei approximation. We incorporate electron exchange and correlations for these processes by using the free-electron-gas model developed earlier for Ps scattering by rare-gas atoms and ${\mathrm{N}}_2$ molecules. The results exhibit similarity between electron and Ps scattering when the cross section is plotted as a function of the projectile velocity, confirming experimental observations [S. J. Brawley et al., Science 330, 789 (2010)]. Below the Ps breakup threshold we observe resonance structures similar to those obtained earlier for Ps-${\mathrm{N}}_2$ scattering.

中文翻译：

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正电子与 O2 和 CO2 的碰撞

我们计算了 Ps 与 Ps 碰撞的弹性和正电子 (Ps) 分解横截面 ${\mathrm{哦}}_2$ 和 ${\mathrm{二氧化碳}}_2$固定核近似中的分子。我们通过使用早先为稀有气体原子的 Ps 散射而开发的自由电子气体模型，将这些过程的电子交换和相关性结合起来，${\mathrm{N}}_2$分子。当横截面被绘制为弹丸速度的函数时，结果显示电子和 Ps 散射之间的相似性，证实了实验观察 [SJ Brawley等人。, Science 330 , 789 (2010)]。在 Ps 破裂阈值以下，我们观察到类似于之前获得的 Ps 共振结构-${\mathrm{N}}_2$ 散射。