High-resolution broad-bandwidth Fourier-transform absorption spectroscopy in the VUV range down to 40 nm

Vacuum-ultraviolet (VUV) high-resolution absorption spectroscopy is a unique tool for the study of gas-phase atomic and molecular electronic structure. To date, it has been performed by using lasers or synchrotron radiation-based grating spectrometers, but none of these techniques can offer simultaneous high resolution, wavelength accuracy and broad tunability. The only technique combining these three important features is Fourier-transform spectroscopy, but this is limited to the mid-UV range (down to 140 nm; ref.1) because of a lack of beamsplitters. Here, we present a new instrument based on a wavefront-division scanning interferometer, applied for the first time to the VUV range. This instrument, coupled to the DESIRS beamline at synchrotron SOLEIL, covers a broad range of wavelengths (typically 7%, adjustable in the 250-40 nm range), a resolving power of similar to 1 x 10(6), an extrinsic absolute wavelength accuracy of 1 x 10(-7) and a high signal-to-noise ratio.