Doublet-quartet transitions in nitric oxide by low-energy variable-angle electron scattering

The electron impact spectrum of nitric oxide between 4 eV and 10 eV energy loss has been studied in detail at impact energies of 25, 35 and 50 eV and at scattering angles between 50 and 800. Weak structure occurring between 5.22 eV and 5.60 eV has been assigned as vibronic bands belonging to the X2PI → a4PI transition. Structure with an apparent Franck-Condon envelope extending from 5.70 eV to approximately 7 eV with intensity maximum at 6.29 eV was assigned to the X2PI → b4Σ- transition. Additional higher lying transitions have been tentatively assigned as doublet → quartet in nature. These represent the first direct observation of doublet → quartet excitations in the gas phase. Several previously unobserved doublet → doublet transitions occurring near 10 eV energy are also reported. (Auth.)