Conductance and Relaxation Time of Electrons in Gold Blacks from Transmission and Reflection Measurements in the Far Infrared

The electrical conductivity of gold blacks is evaluated from reflection and transmission measurements in the far infrared. For sufficiently thin samples and sufficiently large wavelengths a closed expression is derived, relating the electrical conductivity of the gold black directly to the absorption and transmission coefficients. It is found that the electrical conductivity varies with wavelength, and for wavelengths larger than 105 microns this variation is attributed to a relaxation effect. The relaxation time of electrons in gold blacks is found to agree closely with that in bulk gold.