High Resolution Results from the LBL 55-Meter SGM at SSRL Near the K-Edge of Carbon and Nitrogen

The performance of a 55-meter Spherical Grating Monochromator (SGM) is described. A resolution of 60 meV has been achieved at 400eV, inferred from the linewidths of the nitrogen 1 s -π* resonance. A photon flux of 4 × 10 10 photons/s has been observed at 440eV (and with 0.5 eV resolution). An initial experiment has studied the core-shell resonances of gas-phase ethylene, C 2 H 4 . Vibrational fine structure was resolved both for the carbon 1 s -π* and carbon 1 s -Rydberg excitations. Comparison with the vibrational frequencies of ground state ethylene implies that the ν 1 (C-H stretch) and ν 2 (C-C stretch) or ν 3 (H-C-H bend) are excited. It is suggested that the lower Rydberg orbitals, 3 s and 3 p σ, have molecular, anti-bonding character.