Investigation on the Fano Line Shaped Raman Modes of the Hydroxyl and Deuteroxyl Cobalt Chlorides

The low temperature Raman spectroscopic (4000-95 cm–1) investigation on the hydroxyl cobalt chloride Co2(OH)3Cl and deuteroxyl cobalt chloride Co2(OD)3Cl polycrystalline samples has been performed from the room temperature down to 4 K closing to the liquid Helium temperature. Lineshapes of Raman mode Eg (about 130 cm–1 assigned to the normal symmetrically bending vibration mode of the [ClCo3] group for both kinds of samples) are found to be apparently asymmetric Fano lineshapes when the temperatures are below 230 K. This phenomenon is preliminarily attributed to the effect of electron-phonon coupling and a continuum of electronic states centered at about 16 meV with an upper limit 18.5 meV is suggested in this report.