The extension of the hook method to include spatial resolution of nonuniformities in the test plane as suggested by Huber (1971) and Sandeman (1971) is demonstrated experimentally by measurements of the variation of the integrated line density of ground state sodium in a flame. Experiments are also described in which the variations in the flow of CO(2) in a hypersonic shock tunnel are spatially resolved along the spectrometer slit. The variations in the hook separations of the 425.4-nm Cr1 resonance and the 434.4-nm CrI 1-eV lower state line are simultaneously measured. The chromium exists as an impurity in the hypersonic flow of CO(2) over a cylinder in a shock tunnel. The populations of the levels so obtained have enabled the comparison of the excitation temperature of the Cr 1-eV level with the calculated gas temperature.
