Thermal Radiative Properties of the Noble Metals at Cryogenic Temperatures

Experimental values of the monochromatic, near normal emittance, ελN, of gold at cryogenic temperatures are presented and compared with values predicted by existing theoretical models. From this comparison recommendations are made regarding the engineering suitability of these models. Data obtained by the present authors for ελN of gold in the wavelength range 1 to 30μ and at temperatures of 300, 79, and 6.0 K are compared with the Drude free electron model, the anomalous skin effect theory for both specular and diffuse electron reflections, and the Holstein quantum mechanical model. Results show that the anomalous skin effect model with diffuse electron reflections predicts ελN most accurately. At room temperature and at liquid nitrogen temperature the agreement between this model and the data is within 5 percent. At liquid helium temperatures the agreement is somewhat poorer, i.e., within 30 percent.