Frequency/Wavelength Calibration of Multipurpose Multichannel Raman Spectrometers. Part I: Instrumental Factors Affecting Precision

The accuracy of spectra obtained from a Raman spectrometer is limited by the precision of the spectrometer and the calibration process. As the use of multichannel detectors and the complexity of the experiments in which these detectors are employed increase, a need has developed to understand and address the experimental variables that affect the precision of multichannel detector Raman spectrometer systems. The variables examined in this study include alignment of the laser, sample, collection optics, and monochromator; monochromator precision; backlash; thermal effects; resolution; and detector alignment. The magnitude of errors caused by these variables is reported, and procedures employed for acquiring spectra and experimental configuration changes which reduce the magnitude of these errors are discussed. When used in conjunction with the calibration procedure described in the second part of this series, the approaches described here result in accuracies better than ±1 cm⁻¹ for routine Raman experiments and better than ±2 cm⁻¹ for more complex experiments.