Photoconductivity of Crystalline Iodoform II: Photocurrents Induced by a Two-Photon Absorption

Photogeneration of charge carriers in iodoform has been studied using a high power pulsed dye laser as an excitation source. In the region of 480-640 nm, i.e. that of weak absorption, the magnitude of the photogenerated charge follows a square light intensity dependence in the intensity range employed (up to 10²³ photons/cm²s). The spectral dependence of the photogeneration efficiency is similar to that observed for the dc photoconductivity at twice shorter wavelengths; the efficiency drops down, however, rapidly when the tail of the first absorption band of iodoform is approached. Temperature anomalies below 270 K render the exact determination of activation energies impossible.