Baseline Modeling with a Computerized Raman System

A PDP-11-to-Raman spectrometer interface for data acquisition and plotting is described. The background correction problem, which occurs in the transition from data acquisition to the data analysis of chemical interest, has been studied for the nontrivial case of considerable curvature near the Rayleigh wing. The conflict between a baseline function with sufficient freedom to compensate properly for the background and sufficient constraint to achieve uniqueness and reproducibility has been demonstrated. A comparative study has shown the superiority of an exponential-quadratic baseline function over common interpolation procedures such as the cubic spline, the fitting of simple shape-functions to the background, or polynomial expansions.