Wavenumber Calibration Protocol for Raman Spectrometers Using Physical Modelling and a Fast Search Algorithm.

Area of Science:

• Spectroscopy
• Analytical Chemistry
• Physical Chemistry

Background:

• Accurate wavenumber calibration is crucial for Raman spectroscopy analysis.
• Polynomial fitting is a common but potentially less accurate method for calibration.
• Existing calibration methods may struggle with accuracy in specific spectral regions.

Purpose of the Study:

• To propose and validate a novel wavenumber calibration protocol for Raman spectroscopy.
• To replace polynomial fitting with a physically-modeled approach for improved accuracy.
• To introduce new evaluation metrics for assessing calibration performance.

Main Methods:

• Derivation of a mathematical expression based on a physical model of the Raman spectrometer.
• Utilizing system parameters like focal length, grating angle, and laser wavelength.
• Development of a fast search algorithm to identify optimal system parameters using reference standards.
• Application of chemometric cross-validation techniques (leave-one-out, leave-half-out).

Main Results:

• Demonstrated superior accuracy of the physical model-based calibration compared to polynomial fitting.
• Validation across multiple reference standards, systems, and spectral datasets.
• Enhanced performance observed particularly in spectral regions outside outermost reference peaks.
• Successful application to both reflection and transmission gratings.

Conclusions:

• The proposed physical model-based wavenumber calibration offers superior accuracy over polynomial fitting.
• This method provides a more robust and reliable approach for Raman spectroscopy.
• The introduced evaluation metrics offer a standardized way to assess calibration quality.