Compound state electron spectra of simple molecules

Compound negative ion states of molecules N 2 , CO, NO, O 2 , CO 2 , N 2 O and NO 2 have been detected as structure in the total electron scattering cross-sections, interpreted in terms of the Beutler–Fano equation, and partially identified by comparison with isoelectronic species : N 2 -2 ІІ g , 2 eV ; CO -2 II , 1·5 eV ; NO -1 Ʃ + , 1 eV ; O 2 -2 II u , 0·8 eV. The performance of the inverse first-power electrostatic analyser is treated ; it compares satisfactorily with theory provided that preliminary analysis is performed ; otherwise ‘false resonances’ or ghosts may occur.