Use of channeled spectra to measure absolute phase shift and dispersion in two beam interferometry

An application of channeled spectra to two beam interferometry is described in which the optical path to be measured produces a shift of the channeled spectrum from a distribution that is preset in order to minimize the errors involved. This provides an absolute measurement of the phase and dispersion localized at the slit of the spectrometer with an improvement in accuracy over monochromatic or two wavelength interferometry. Examples include a time resolved channeled spectrum of the electron, ion, and neutral densities behind a strong shock wave in argon.