Intercomparison of radiometric irradiance scales in the 90-250-nm wavelength range

Different calibration methods for far-UV sources and detectors are compared by measuring the absolute quantum efficiencies of two different transfer standards calibrated by the NBS and ARD. The agreement of the spectral irradiance scales of the laboratories in the UV spectral range was satisfactory at wavelengths greater than 120 nm. The somewhat poor agreement at wavelengths shorter than 120 nm mainly resulted from experimental problems due to strong reflection losses of the optical components in the test setups. However, the agreement between the arc-based and the detector-based methods found at all wavelengths is well within the estimated uncertainties of both techniques.