Use of bound state methods to calculate partial and total widths of shape resonances.

In this work we study the Π resonances of a two-site model system designed to mimic a smooth transition from the Π temporary anion of N to the Π temporary anion of CO. The model system possesses the advantage that scattering and bound state () methods can be directly compared without obfuscating electron-correlation effects. Specifically, we compare resonance parameters obtained with the complex Kohn variational (CKV) method with those from stabilization, complex absorbing potential, and regularized analytical continuation calculations.

Role of Overlap between the Discrete State and Pseudocontinuum States in Stabilization Calculations of Metastable States.

In a diabatic picture metastable states subject to decay by electron detachment can be viewed as arising from the coupling between a discrete state and a continuum. In treating such states with bound-state quantum chemical methods, the continuum is discretized. In this study, we elucidate the role of overlap in this interaction in the application of the stabilization method to temporary anion states.

A Fresh Look at the Role of the Coupling of a Discrete State with a Pseudocontinuum State in the Stabilization Method for Characterizing Metastable States.

The stabilization method is widely used to theoretically characterize temporary anions and other systems displaying resonances. In this approach, information about a metastable state is encoded in the interaction of a diabatic discrete state and discretized continuum solutions, the energy of which are varied by scaling the extent of the basis set. In this work, we identify the aspects of the coupling between the discrete state and the discretized continuum states that encode information about the existence of complex stationary points and, hence, complex resonance energies in stabilization graphs.

Prediction of a Non-Valence Temporary Anion State of (NaCl).

The equation-of-motion coupled cluster method is used to characterize the low-lying anion states of (NaCl) in its rhombic structure. This species is known to possess a non-valence bound anion of A symmetry. Our calculations also demonstrate that it has a non-valence temporary anion of B symmetry, about 14 meV above threshold.

Prediction of a Nonvalence Temporary Anion Shape Resonance for a Model (HO) System.

Ab initio calculations are used to demonstrate the existence of a nonvalence temporary anion shape resonance for a model (HO) cluster system with no net dipole moment. The cluster is composed of two water dimers, the distance between which is varied. Each dimer possesses a weakly bound nonvalence anion state.

Ab initio calculation of the cross sections for electron impact vibrational excitation of CO via the (2)Π shape resonance.

The stabilization method is used to calculate the complex potential energy curve of the (2)Π state of CO(-) as a function of bond length, with the refinement that separate potentials are determined for p-wave and d-wave attachment and detachment of the excess electron. Using the resulting complex potentials, absolute vibrational excitation cross sections are calculated as a function of electron energy and scattering angle. The calculated cross sections agree well with experiment.

Assessment of various electronic structure methods for characterizing temporary anion states: application to the ground state anions of N2, C2H2, C2H4, and C6H6.

The theoretical characterization of temporary anions is an especially challenging problem. In the present study we assess the performance of several electronic structure methods when used in conjunction with the stabilization method to characterize temporary anion states. The ground state anions of N2, C2H2, C2H4, and C6H6 are used as the test systems, with the most extensive testing being done for N2.