Many impurity atoms in a semiconductor exchange energy and electrons with the electrons in the conduction band. consider the impurity atoms to be in thermal and chemical equilibrium with the conduction band, which can be considered to be both an energy and particle reservoir. assume that a is the ionization energy of the impurity atom. find the probability that an impurity atom is ionized as a function of δ and the chemical potential μ. [hint: consider the electrons with spin "up" or spin "down"]