Infrared absorption and reflection studies of organic radical salt: K+TCNQminus;

摘要

The bulk reflectivity and absorption (using alkali halide matrices and thin film dispersions) of polycrystalline K+TCNQminus;in the wavelength range between 30 and 4000 cmminus;1have been examined in detail. The sharp reflectivity peaks have been analyzed using a classical oscillator fitting procedure to give the peak and oscillator parameters. Most of the observed infrared peaks have been assigned to the fundamental modes of TCNQminus;and lattice vibrations. The temperature dependence of the CN stretching peaks in particular have been studied in the 300ndash;433thinsp;deg;K temperature range. The reversible and gradual disappearance of one set of CN stretching peaks in K+TCNQminus;has been tentatively linked to a possible cell halving phase transition atTcsim;379thinsp;deg;K. The results are compared with the spectrum of Rb+TCNQminus;which is isomorphous with the postulated high temperature phase of K+TCNQminus;.