A chirped pulse fourier transform microwave spectrometer

“超流动性”是一个集合术语，用于描述体积氦在其2.17 K的转变温度以下所表现出的迷人特性（如消失的粘度）和不寻常的效应（如喷泉效应）。超流动性是量子效应在宏观尺度上的表现，要求微观组分为玻色子，即具有整数复合自旋。除了氦，只有一个系统可能表现出超流体效应，即分子氢，H2。氢以两种自旋修饰形式出现，总自旋I=0的paraH2和I=1的orthh2。与正h2相比，para ah2的分子间相互作用较弱，预计其向超流体的转变温度（7 K）更高。然而，到目前为止，大块paraH2中的超流动性尚未得到实验验证，因为它在13k时就已经凝固了。

'Superfluidity' is a collective term for the fascinating properties (e.g. vanishing viscosity) and unusual effects (e.g. fountain effect) which bulk helium exhibits below its transition temperature of 2.17 K. Superfluidity is a manifestation of quantum effects on the macroscopic scale and requires that the microscopic constituents are bosons, i.e. have an integer composite spin. Besides helium, there is only one other system which may show superfluid effects, namely molecular hydrogen, H2. Hydrogen occurs as two spin modifications, paraH2 with total spin I=0 and orthoH2 with I=1. paraH2 is expected to have the higher transition temperature to superfluidity (7 K) because of its weaker intermolecular interactions compared to orthoH2. However, superfluidity in bulk paraH2 has thus far escaped experimental verification because it solidifies already at 13 K.