Uwe Arp, Zhigang Li, Ping-Shine Shaw, Mathias Richter, Roman Klein, Wolfgang Paustian, Reiner Thornagel
We report on a successful bilateral inter-comparison between the Physikalisch-Technische Bundesanstalt (PTB) and the National Institute of Standards and Technology (NIST). In both laboratories deuterium lamps were calibrated using the calculability of synchrotron radiation. However, the methods applied in both laboratories differed significantly. Whereas the calibrations at PTB were performed in vacuum and let to spectral radiant intensities, the measurements at NIST were done in air and resulted in spectral irradiances. Therefore, for this bilateral comparison did we not only prove the equivalence of the two measurement procedures, but also the validity of the conversion between the different spectro-radiometric quantities. This successful comparison reestablishes the usefulness of deuterium lamps as transfer standards in the ultraviolet spectral range.