A Semiquantum Liquid and a New Ordered Phase of ⁴He Adsorbed in Y Zeolite

A fluidity and a quantum effect of a new helium 4 system, unsaturated 4 He adsorbed in a narrow void channel of Y-zeolite crystal, have been studied by measuring the heat capacity. In the case of the quantity adsorbed n =0.445 ×10 -3 mol/g, the heat capacity C is proportional to the temperature, i.e. C = n α T , in the condition T c (=3.25 K)\( \leqq T \lesssim 9\) K, and it reduces suddenly below T c . The coefficient α is 2.2 J/K 2 /mol. The experimental result shows that the state above T c is a semiquantum liquid such as bulk 4 He which remains liquid to much lower temperatures than the Debye temperature. Below T c , the result indicates the presence of an ordered state.

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