Search for H2- resonances in the detachment of H- by electron impact with a high-resolution cooler ring

Molecular size effect in NCO and NCS dianion resonances

Cross sections for electron-impact detachment and electron-impact dissociation of NCO- and NCS- were measured from about 3 to about 40 eV. The former are found to follow a classical prediction with a threshold energy of 9.1 +/- 0.1 eV for NCO- and 8.9 +/- 0.2 eV for NCS-. When the incoming electron binds to the monoanion, a short-lived dianion complex is formed, which is revealed as a resonance in the cross section. For NCO- a resonance is evident at 9.3 +/- 0.2 eV, which implies that the dianion lies above the monoanion by this amount of energy. In the case of NCS- two resonances are evident at 8.4 +/- 0.2 and 19.0 +/- 0.5 eV, respectively. The low-energy NCS dianion is less unstable than the dianion of NCO, which in turn is less unstable than the CN dianion (10-eV resonance). Thus the resonance shifts down in energy with the increasing size of the anion, a fact which is attributed to a decrease in Coulomb energy between the spatially separated electrons.

Electron scattering on centrosymmetric molecular dianions Pt(CN)4(2-) and Pt(CN)6(2-)

Electron scattering on stored Pt(CN)2-4 and Pt(CN)2-6 centrosymmetric molecular dianions has been performed at the electrostatic storage ring ELISA. The thresholds for production of neutral particles by electron bombardment were found to be 17.2 and 18.7 eV, respectively. The relatively high thresholds reflect the strong Coulomb repulsion in the incoming channel as well as a high energetic stability of the target electrons. A trianion resonance was identified with a positive energy of 17.0 eV for the Pt(CN)2-4 square-planar complex, while three trianion resonances were identified for the Pt(CN)2-6 octahedral complex with positive energies of 15.3, 18.1, and 20.1 eV.

Resonance states of atomic Di-anions

Metastable states of O (2-), S (2-), B (2-), and Al (2-) are studied in the framework of the complex absorbing potential method using highly correlated multireference configuration interaction wave functions. The first row species O (2-) and B (2-) are found to be broad resonances showing widths of roughly 1.7 eV, whereas the second row systems S (2-) and Al (2-) possess widths clearly smaller than 1 eV. The identified resonance states are compared to the fundamental H (2-) resonance, and the relationship with recent electron scattering experiments is discussed.