The atom 3 He has spin I = and is a fermion. (a) Calculate as in

The atom ³He has spin I = ½ and is a fermion.

(a) Calculate as in Table 7.1 the Fermi sphere parameters v_F, ε_F, and T_F for ³He at absolute zero, viewed as a gas of non-interacting fermions. The density of the liquid is 0.081 g cm^–3.

(b) Calculate the heat capacity at low temperatures T << T_F, and compare with the experimental value C_v = 2.89Nk_aT as observed for T < 0.1 K by A. C. Anderson, W. Reese, and J. C. Wheatley, Phys, Rev. 130, 495 (1963); see also Figure. Excellent surveys of the properties of liquid ³He are given by J. Wilks, Properties of liquid and solid helium, Oxford, 1967, and by J. C. Wheatley, Di1ute solutions of ³He in ⁴He at low tern peratures,” American Journal of Physics 36, 181–210 (1968). The principles of refrigerators based on ³He– ⁴He mixtures are reviewed in Chapter on cryogenics; such refrigerators produce steady temperatures down to 0.01 K in continuously acting operation.

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5.0: коркоро Pure 3He 2.0 1.0 -5% ЗНе in 1He 0.5 0.2 10 20 50 100 200 Temperature, in к C/T, rclative scale