Calculate the temperature dependence of the heat capacity of p-H₂ (in which only rotational states with even values of J are populated) at low temperatures on the basis that its rotational levels J = 0 and J = 2 constitute a system that resembles a two-level system except for the degeneracy of the upper level. Use B = 60.864 cm⁻¹ and sketch the heat capacity curve. The experimental heat capacity of p-H₂ does in fact show a peak at low temperatures.