Electron-atom resonances: The complex-scaled multiconfigurational spin-tensor electron propagator method for the2PBe−shape resonance problem

Abstract

We propose and develop the complex scaled multiconfigurational spin-tensor electron propagator (CMCSTEP) technique for theoretical determination of resonance parameters with electronatom/molecule systems including open-shell and highly correlated atoms and molecules. The multiconfigurational spin-tensor electron propagator method (MCSTEP) developed and implemented by Yeager his coworkers in real space gives very accurate and reliable ionization potentials and attachment energies. The CMCSTEP method uses a complex scaled multiconfigurational selfconsistent field (CMCSCF) state as an initial state along with a dilated Hamiltonian where all of the electronic coordinates are scaled by a complex factor. CMCSCF was developed and applied successfully to resonance problems earlier. We apply the CMCSTEP method to get 2 P Be − shape resonance parameters using 14s11p5d, 14s14p2d, and 14s14p5d basis sets with a 2s2p3d CAS. The obtained value of the resonance parameters are compared to previous results. This is the first time CMCSTEP has been developed and used for a resonance problem. It will be among the most accurate and reliable techniques. Vertical ionization potentials and attachment energies in real space are typically within ±0.2 eV or better of excellent experiments and full configuration interaction calculations with a good basis set. We expect the same sort of agreement in complex space.

Calculations for electron-impact excitation and ionization of beryllium

“…These parameters differ considerably from the numerous results obtained with model potentials [27] or complexrotation-based methods [28] methods.…”

“…The above shape resonance in elastic e-Be scattering has been the subject of numerous calculations with different methods. An overview of the many predictions is given in Table III of [28]. The results differ considerably, ranging for positions from 0.1 eV to 1.2 eV and widths from 0.14 eV to 1.78 eV, respectively.…”

Second order Møller-Plesset and coupled cluster singles and doubles methods with complex basis functions for resonances in electron-molecule scattering

“…Feshbach resonances in particular have lifetimes that are entirely determined by electron correlation. While correlated calculations on atomic resonances are fairly routine, [40][41][42][43] correlated calculations on molecular resonances are not as commonplace. Electron correlation effects on resonance parameters in electron-molecule scattering have been incorporated into a variety of methods.…”

Shape resonances of Be$^-$ and Mg$^-$ investigated with method of analytic continuation

“…While in the case of the Mg − the agreement between the available computed resonance parameters [26][27][28] and the experimental data [29,30] is quite good, the situation is very different for the beryllium atom. There has been a great number of theoretical studies [31][32][33][34][35][36][37][38][39][40][41][42] aiming to numerically characterize Be − 2s 2 εp 2 P resonance, with various levels of success. Table III in Ref.…”