Characterization of the double sulfites Cu2SO3·MSO3·2H2O (M = Cu, Fe, Mn or Cd) by photothermal techniques

Abstract

Structural, thermal and optical properties as well as the non-radiative relaxation time τ_R and the characteristic diffusion time τ_β of the synthesized double sulfites Cu₂SO₃ ·MSO₃·2H₂O (M = Cu, Fe, Mn or Cd) were investigated by photoacoustic spectroscopy. The positions of the bands for each compound were identified upon gaussian deconvolution and by Kramers–Kronig analysis, and the d–d and intervalence transitions were observed. The detection of two absorbing bands with low and high intensities is in agreement with previous results on reflectance for Cu₂SO₃CuSO₃·2H₂O. A slight shift is observed in the peak positions and in the measured thermal diffusivity, capacity and conductivity for different Ms and the thermal conductivity decreases with the ionic radius of the M(II) cations.