Infrared Hole-Burning of Crystalline Ammonium Copper Tutton Salt: Tunneling Kinetics and Jahn−Teller Distortions

Abstract

Irradiation of the N−D stretching band in crystalline deuterium-doped ammonium copper Tutton salt rotates the ammonium ion and changes the conformation of molecules about the copper. The crystal salt exists in at least two different crystal forms, each form containing a particular Jahn−Teller distorted copper conformation. We consider only the “A” form crystal. In this crystal, the minority conformation (B) appears with the majority conformation (A) as the temperature is raised. The spectral holes and antiholes produced by the changes in conformation occur in patterns that depend on the exact frequency of irradiation. Each pattern appears and eventually decays with different kinetics over a range of times. The variation of the hole widths, measured at different temperatures, reveals the presence of various conformations in the crystal lattice. This inhomogeneity is related to the statistical distribution of conformations A and B weighted by their thermal populations. The kinetics of the decay of the holes...