EVALUATION OF A CORRECTION FOR PHOTOMETRIC ERRORS IN FT-IR SPECTROMETRY INTRODUCED BY A NONLINEAR DETECTOR RESPONSE

For strongly absorbing bands measured with a Fourier transform infrare d (FT-IR) spectrometer, the effects of a nonlinear detector response m ust be eliminated before Beer's law linearity can be achieved. An empi rical method for greatly reducing the effect of detector nonlinearity on FT-IR Beer's law spectra measured by using an FT-IR spectrometer eq uipped with a mercury-cadmium-telluride (MCT) detector is investigated . This first-order analytical function has been applied to correct non linear vapor-phase spectra and statistically evaluated for validity fo r spectral regions above the detector cutoff, In addition, a series of second-order functions has been evaluated to investigate the possibil ity that the transmittance scale is slightly nonlinear even after the first-order correction has been applied. Any improvement caused by the second-order functions was not statistically significant.