Spectroscopic analysis methods

Abstract

A spectroscopic analysis method in which spectral data of mixtures obtained from a plurality of points on a sample surface are resolved into component spectra and concentrations. A new alternating least squares multivariate curve resolution technique is presented which iteratively resolves the components. The technique starts from an initial estimate that the spectral values of a first component of the sample are all equal (an 'empty model'), and resolves that component. Then successive further components are iteratively resolved, from initial 'empty model' estimates of those components and from previously resolved spectra. In the common case where the main component is present in nearly pure form in the data set, this empty modelling technique results in more accurate resolution of the components. This is due to the ability of the technique to resolve the pure spectra of minor components without modelling concentrations of the main component into them.

Description

technical field

[0001] The present invention relates to spectroscopic instruments and methods. It is particularly useful in Raman spectroscopy, although the invention can also be used in other forms of spectroscopy, for example using narrow line photoluminescence, fluorescence, cathodoluminescence or infrared. Background technique

[0002] The Raman effect is a phenomenon in which a sample scatters incident light of a given frequency into a spectrum having lines resulting from the interaction of the incident light with the molecules that make up the sample. Different compounds have different characteristic Raman spectra, and thus this effect can be used to analyze the compounds present.

[0003] Examples of Raman spectrometers are known from US Patent Nos. 5,442,438 and 5,510,894, which are incorporated herein by reference. The sample is illuminated with monochromatic light from a laser. Typically, the scattered light is then dispersed into a Raman spectrum by a dispersiv...

Images