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 position‐sensitive photon‐counting detector provide spectra of low‐intensity luminescence. This method has been demonstrated on two luminescent materials, europium (II)‐doped barium fluorobromide [BaFBr/Eu(II)] and uranyl nitrate [UO2(NO3)2∙6H2O]. Pixel‐by‐pixel division of a luminescence image taken through the filter by an image without the filter corrects for variations in image intensity. The intensity along the long axis of the filter after correction for detector sensitivity constitutes a luminescence emission spectrum. BaFBr/Eu(II) gave delayed emission with a maximum intensity at 395 nm, in reasonable agreement with the 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 ∼600 nm. These did not correspond to experimental fluorescence maxima due to differing self‐absorption effects.