Scattering resonances are relatively rare in positron scattering, with the only observed instances to date being vibrational Feschbach resonances, observed through their effect on the annihilation cross section. In this study, we present observations of resonances in vibrational excitation by positron impact on ethane, ethylene, and acetylene, and explore the dynamics of positron resonance formation and decay. There are far fewer resonances observed in the excitation spectra than in the annihilation channel. Due to the difficulties inherent in measuring relevant scattering processes at the low energies required to observe the resonances, the formation and decay modes of these resonances are still not well understood. Theory suggests that intramolecular vibrational energy redistribution plays a key role in resonance formation and decay, which should lead to enhancement of the vibrational excitation cross sections in the region of the resonance energies. These results demonstrate that further work is required to fully understand these systems.

中文翻译：

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振动激发中的正电子共振

散射共振在正电子散射中相对罕见，迄今为止唯一观察到的实例是振动费施巴赫共振，通过其对湮没截面的影响观察到。在这项研究中，我们观察了正电子撞击乙烷、乙烯和乙炔的振动激发中的共振，并探索了正电子共振形成和衰变的动力学。在激发光谱中观察到的共振比在湮没通道中少得多。由于在观察共振所需的低能量下测量相关散射过程固有的困难，这些共振的形成和衰变模式仍然没有得到很好的理解。理论表明，分子内振动能量重新分布在共振形成和衰减中起着关键作用，这应该导致共振能量区域中振动激发截面的增强。这些结果表明，需要进一步的工作才能充分理解这些系统。