A survey of the salts of the rare‐earth series shows that anhydrous PrCl3has energy levels and selection rules suitable for use in a solid state infrared quantum counter as proposed by Bloembergen [N. Bloembergen, Phys. Rev. Letters2, 84 (1959)]. Two suitable schemes are proposed, one for detection at 2.33 &mgr; and a second for detection at 104 &mgr;. Consideration is given to isolation of the final detector from the pumping signal and a suitable experimental arrangement for unambiguously determining proper operation is shown.