X-ray emission spectra of small molecules

An instrument for X-ray emission studies of free molecules is described and electron and fluorescence excitations are discussed. The application of X-ray emission spectroscopy to free molecules is exemplified by the spectra of N₂, CO, NO and CO₂. From the spectra the core level binding energies of the molecules are deduced. For the diatomic molecules vibrational fine structure is resolved and analyzed in terms of different bond lengths in the initial and final states. The change in bond length, when the initial 1 s vacancy is formed, is also discussed. The influence of the X-ray selection rules and molecular localization properties on the band intensities are discussed and exemplified by the O1 s and C1 s spectra of CO and CO₂. In the spectra about ten satellites are found.