A chirped pulse fourier transform microwave spectrometer

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'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.