SPECTRAL RESOLUTION OF DIFFUSE LUMINESCENCE BY IMAGING WITH A POSITION-SENSITIVE DETECTOR THROUGH A VARIABLE WAVELENGTH INTERFERENCE FILTER

The combination of a variable wavelength interference filter and a pos ition-sensitive photon-counting detector provide spectra of low-intens ity luminescence. This method has been demonstrated on two luminescent materials, europium (II)-doped barium fluorobromide [BaFBr/Eu(II)] an d uranyl nitrate [UO2(NO3)2.6H2O]. Pixel-by-pixel division of a lumine scence image taken through the filter by an image without the filter c orrects for variations in image intensity. The intensity along the lon g axis of the filter after correction for detector sensitivity constit utes a luminescence emission spectrum. BaFBr/Eu(II) gave delayed emiss ion with a maximum intensity at 395 nm, in reasonable agreement with t he measured Eu 5d-->4f fluorescence maximum that occurs at 389 nm. The same technique applied to UO2(NO3)2.6H2O gave peaks at 511, 539, 567, and approximately 600 nm. These did not correspond to experimental fl uorescence maxima due to differing self-absorption effects.