Internal dynamics and "superfluidity" in small helium and hydrogen clusters

由几个到几十个氦原子或氢分子掺杂探针分子组成的小团簇将被毫米波光谱研究，以表征这些团簇的性质与它们的大小有关。本研究旨在解决与超流体微观性质相关的基本问题，即，超流体的开始需要多少氦原子以及氢是否可以成为超流体？用超高灵敏度腔内光谱仪OROTRON测量了超声速射流中冷团簇的旋转光谱。由于这些系统的性质与纯氦或纯氢团簇非常相似，并且与其他系统相比，迄今为止还没有记录到纯旋转光谱，因此活性将仅限于掺杂一氧化碳，HeN-CO和（H2）N-CO的团簇。此外，在小到中等簇大小范围内，建立络合物的旋转动力学与其超流体响应的关系是本提案的目标。

Small clusters counting a few to several tens helium atoms or hydrogen molecules doped with a probe molecule will be investigated by millimeter-wave spectroscopy in order to characterize the properties of these clusters in dependence on their size. This study is intended to address fundamental questions related to the microscopic nature of superfluidity, namely, what number of helium atoms is required for the onset of superfluidity and whether hydrogen can be made superfluid? Rotational spectra of cold clusters in a supersonic jet will be measured with the ultrahigh sensitivity intracavity spectrometer, OROTRON. Activities will be constrained to clusters doped with carbon monoxide, HeN-CO and (H2)N-CO, since the properties of these systems are very similar to those of pure helium or hydrogen clusters and in contrast to other systems to date no pure rotational spectra have been recorded. Furthermore, establishment of a relation of rotational dynamics of the complex to its superfluid response in the small to intermediate cluster size regime are the goals of present proposal.