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Collisional losses of magnetically trapped cold methyl radicals Hu, Jiahong


Collisions between cold polyatomic molecules and atoms are essential in various processes, including interstellar chemical reactions, quantum tunneling, and precision measurements.The methyl radical was the rst polyatomic radical trapped in a magnetic trap. This was achieved by our group in 2017, where the trapped radicals were trapped at a temperature of approximately 130 mK. The methyl radical has been proposed as a potential candidate for sympathetic cooling, which can achieve temperatures below 1 mK. In order to elucidate the collisional properties of the methyl radical, collisions between magnetically trapped, cold methyl radicals, and room temperature helium and argon atoms were investigated experimentally. This work presents the results of these collisional studies and their comparison with theoretically derived trap loss rates. Quantum diffractive collisions dominate the collisions between room temperature helium atoms and cold methyl radicals in a magnetic trap with a trap depth of about 134 mK. More than 10 % of trap loss is attributed to inelastic collisions, in which the methyl radicals are excited to a rotationally excited state. On the other hand, collisions between cold methyl radicals and room temperature argon at this trap depth is near the border between quantum diffractive collisions and classical collisions.

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