QUANTITATIVE INVESTIGATION OF CHARGE-TRAPPING EFFECTS ON RAMAN-SPECTRA ACQUIRED USING CHARGE-COUPLED-DEVICE (CCD) DETECTORS

Changes in spectral band parameters (width, center frequency, intensity) which arise from charge-trapping artifacts in the Thomson TH 7882 charge-coupled-device (CCD) detector are reported. These parameters are measured for a Raman scattering band of carbon tetrachloride with respect to CCD geometry (parallel vs. serial binning), in the presence and absence of preflash, vs. changes in integration time (variation in detected light level). The dependence of the spectral parameters on detector temperature was also measured. The degree of charge trapping and the charge transfer efficiency were estimated from the change in peak width and intensity vs. integration time, respectively, and were found to vary with detector temperature according to an Arrhenius relationship for the serial-binning geometry; from these results, the energy barriers to charge trapping and loss in the serial register were estimated. Practical guidelines for acquisition of binned spectra with this detector are suggested.