AN EASY TO BUILD, HIGH-INTENSITY MONOCHROMATOR FOR HELIUM-II RADIATION APPLIED TO INNER VALENCE PHOTOELECTRON STUDIES OF SMALL MOLECULES

An easy to build, high intensity monochromator for helium II radiation is presented. The design includes a double focusing, nonblazed, toroidal grating with a groove density of 800 l/mm. The adjustment and focusing properties of the design have been studied using an optical simulation program. It is found that all necessary adjustments of the grating may be performed by using only two degrees of freedom; rotation and sidewise shifting. Inner and outer valence photoelectron spectra of N2 and CO have been recorded using monochromatized HeII-alpha radiation. The study reveals extensive vibrational structures in the inner valence region of both molecules. A new state has been identified in the CO molecule.