Degradation of the diffuse reflectance of Spectralon under low-level irradiation

SpectralonTM is a well known diffuse reflectance standard. Although ageing effects of Spectralon under high-level VUV and air UV irradiation have been reported, Spectralon is assumed to be stable under the normal radiation conditions used for calibration in standard facilities. In this paper, ageing effects of Spectralon under low-level irradiation and in the dark are presented. It has been found that ageing is mainly affected by four parameters: wavelength of radiation, irradiance level, radiant exposure (dose) and storage time of the samples. Therefore, the use of SpectralonTM as a transfer standard in international comparisons and maintenance of reference values is discussed.