Switching the Jahn−Teller Distortion in Crystalline Ammonium Hexaaquacopper Sulfate (Tutton Salt) with Infrared Radiation

The N−D and O−D stretching regions of the infrared spectrum of (NH4)2[Cu(H2O)6]SO4 doped with a small amount of deuterium reflect the known structure of the crystals at 7 K. Irradiation at the wavenumber of any one of the N−D bands yields spectral holes and antiholes that are doubled, indicating the presence of two different conformations in the crystals. The infrared-induced changes in the N−D bands are coupled to the changes in the O−D bands, and these in turn are coupled to the Jahn−Teller distortions about the copper. The holes and antiholes decay back to equilibrium in a complicated nonmonotonic way. Irradiating the O−D bands also produces holes and antiholes in contrast to the situation for other Tutton salts.