Abstract: A method for processing a workpiece and an associated processing chamber and analytic instrument. A layer of a material such as a low-K dielectric is applied to a workpiece such as a semiconductor wafer. During the application, and/or before or during subsequent processing, a property of the layer is measured by steps including exciting a portion of the layer with incident light and monitoring light such as Raman scattered light that is emitted from that portion of the layer in response to the incident light, via a probehead that may be inside or outside the chamber housing. The analytic instrument includes the probehead and two sources of excitation light at two different wavelengths.