A unique spectroscopic device combining a Fourier transform infrared spectrometry instrument and a very-long-pathlength cell (a few hundred meters) is described. It shows much promise for spectroscopic studies of unstable or transient species at extremely low concentrations in a temperature-controlled environment. Results are presented of dioxygen difluoride (O2F2) fluorination reactions with Pu compounds and of O2F2 thermal stability measurements in the cell.
