We describe the design and construction of an experimental cell for the study of free radicals in macroscopically thick films of solidified molecular and rare gases by 128 GHz Electron Spin Resonance (ESR) at temperatures below 1 K. The ESR resonator has an open Fabry-Pérot design, and its frequency can be tuned in situ by adjusting the spacing between the mirrors. The tuning mechanism consists of a piezo positioner and a stainless-steel edge-welded bellows, which can change the resonator frequency by at least 6 GHz. The films of solidified gases can be deposited either directly from a room temperature reservoir or by recondensing from a specially arranged chamber. The free radicals can be created in the solid films by dissociating matrix species by running an rf discharge in a helium vapor. We suggest that such a sample cell design can also be used for a broad range of low-temperature ESR experiments where sample cooling needs to be enhanced by the presence of superfluid helium.

中文翻译：

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带有原位调谐法布里-珀罗谐振器的实验池，用于在低于 1 K 的温度下对基质分离自由基进行磁共振研究

我们描述了一个实验单元的设计和构造，用于在低于 1 K 的温度下通过 128 GHz 电子自旋共振 (ESR) 研究固化分子和稀有气体的宏观厚膜中的自由基。 ESR 谐振器具有开放的 Fabry-Pérot设计，它的频率可以通过调整镜子之间的间距来原位调谐。调谐机构由压电定位器和不锈钢边焊波纹管组成，可将谐振器频率改变至少 6 GHz。固化气体的薄膜可以直接从室温储存器中沉积，也可以通过从特殊布置的腔室中重新冷凝来沉积。自由基可以通过在氦气中进行射频放电使基质物质解离而在固体薄膜中产生。