1Se resonance States of two electron atoms by stabilization method (original) (raw)
Related papers
2021
In this paper, resonance energies and excitation energies of doubly 2sns 1,3Se, 2snp 1,3P0, 2pnp 1,3De, 2pnd 1,3F0 and 2pnf 1,3Ge excited states of the helium isoelectronic sequence with Z ≤ 10 are calculated. Calculations are carried out in the framework of the variational procedure of the formalism of the Screening Constant per Unit Nuclear Charge (SCUNC). New correlated wave function of Hylleraas type is used. Precise resonance and excitation energies are tabulated and good agreement is obtained when a comparison is made with available literature values.
Perturbation Study of Some Excited States of Two-Electron Atoms
Physical Review, 1969
A perturbation study of the && states of two-electron atoms has been made. In particular, oscillator strength values for the (1 8, 2 P) and (2 S, 2 P) transitions are obtained. The 2 P and 2 I' states are studied through ninth and tenth order, respectively. In addition, the N I' and N Pstates are studied in first order through the 10P member of the series. Perturbation energy coefficients and other expectation values for several important operators have been computed. Perturbation energy coefficients for the 1 8 state (through 25th order) and 2 S state (through 17th order) are also reported. Where comparison is possible, these results are in satisfactory agreement with the results obtained from variational calculations by C. L. Pekeris and co-workers. The variational-perturbation method for excited states requires auxiliary conditions on the perturbation wave functions. The condition on the nth-order wave function is derived here. This is a generalization of the first-order condition given by Sin anoglu.
Doubly excited states of two-electron atoms
Chemical Physics Letters, 2009
Precise energy eigenvalues of doubly excited 1;3 D o states originating from 2pnd ðn ¼ 3-8Þ configuration of two-electron atoms ðZ ¼ 3-7Þ have been calculated by using Ritz variational method in Hylleraas coordinates. Except for a few, the present non-relativistic energy values are the lowest yet obtained. The energy eigenvalues of a number of these states are being reported for the first time. Comparisons with existing experimental results are also made. The effective quantum numbers ðn Ã Þ for the states mentioned above have been calculated using the theory of quantum defect.
Resonance states of atomic anions
We study destabilization of an atom in its ground state with decrease of its nuclear charge. By analytic continuation from bound to resonance states, we obtain complex energies of unstable atomic anions with nuclear charge that is less than the minimum "critical" charge necessary to bind N electrons. We use an extrapolating scheme with a simple model potential for the electron, which is loosely bound outside the atomic core. Results for O 2− and S 2− are in good agreement with earlier estimates. Alternatively, we use the Hylleraas basis variational technique with three complex nonlinear parameters to find accurately the energy of two-electron atoms as the nuclear charge decreases. Results are used to check the less accurate one-electron model.
Extensions of the complex-coordinate method to the study of resonances in many-electron systems
Physical Review A, 1978
DiAiculties in the straightfoward application of the complex-coordinate method to the calculation of resonance states in many-electron systems are examined. For the case of shape resonances, it is shown that many of these difficulties can be avoided by using complex coordinates only after reduction of the system to an effective one-electron problem. Further simplifications are achieved by the use of an inner-projection technique to facilitate the computation of the complex Hamiltonian matrix elements. The method is first illustrated by application to a model-potential problem. Its suitability for studying many-electron problems is demonstrated by calculation of the position and width of a low-energy P' shape resonance in Be. We discuss the modifications necessary to study core-excited (Feshbach) resonances.
On a simple way to calculate electronic resonances for polyatomic molecules
Journal of Chemical Physics, 2015
We propose a simple method for calculation of low-lying shape electronic resonances of polyatomic molecules. The method introduces a perturbation potential and requires only routine bound-state type calculations in the real domain of energies. Such a calculation is accessible by most of the free or commercial quantum chemistry software. The presented method is based on the analytical continuation in a coupling constant model, but unlike its previous variants, we experience a very stable and robust behavior for higher-order extrapolation functions. Moreover, the present approach is independent of the correlation treatment used in quantum many-electron computations and therefore we are able to apply Coupled Clusters (CCSD-T) level of the correlation model. We demonstrate these properties on determination of the resonance position and width of the 2 Π u temporary negative ion state of diacetylene using CCSD-T level of theory.
2020
In this work, the total energies of doubly excited states (ns2) 1Se, (np2) 1De, (nd2) 1Ge, (nf2) 1Ie, (ng2) 1Ke, and (nh2) 1Me of the helium isoelectronic sequence with Z ≤ 10 are calculated in the framework of the variational method of the Screening Constant by Unit Nuclear Charge (SCUNC). These calculations are performed using a new wavefunction correlated to Hylleraas-type. The possibility of using the SCUNC method in the investigation of high-lying Doubly Excited States(DES) in two-electron systems is demonstrated in the present work in the case of the (nl2) 1Lπ doubly excited states, where accurate total energies are tabulated up to n = 20. All the results obtained in this paper are in agreement with the values of the available literature and may be useful for future experimental and theoretical studies on the doubly excited (nl2) 1Lπ states of two-electron systems.
Theoretical studies of core-excited states of two- and three-electron atoms
Physical Review A, 1981
We have carried out configuration-interaction calculations for 'F" states of Li and Be+ and for the lowest 'D" states of Be+ in an effort to test the accuracy that can be achieved in transition-energy calculations by assuming transferability of relativistic, radiative, and mass-polarization corrections among similar electron cores. He and Li+ 2p4f 'F states have also been considered. The nonrelativistic result for the Li 1s2p4f 'F-+1s2s4f 'F' transition is A, , = 5474.3~0.4 A. Including relativistic, radiative, and mass-polarization corrections for the 1s2p P and ls2s S Li+ cores we get A, = 5471.7~0.4 A, in excellent agreement with a A, = 5471.9+1. 4 A recently observed in the beam-foil source. Stronger support for our basic assumption comes from three calculated (experimental) wavelengths A, = 3406.0~0.3{3405. 6~0. 6), 4330.1~0.5(4330.2~0. 5), and 3510.8~0.5(3510.8~0.5) A in the Be n~~s pectrum. Furthermore, three lines (the Grst two above and A, = 981 A) have been reassigned and three new wavelengths are predicted for this spectrum. The 1s2s4f~1s2p 3d nature of the 4F'(1) and 'F'(2) states in Be+ is responsible for the uncommon situation that 'F'(1) is below 1s2s4d 'D'(2), thus explaining the failure of some of the earlier assignments. The lowest Be+ 1s2s2p 'P' state is found 115.845~0.016 eV above the Be+ 1s'2s ground state, in fair agreement with a recent experimental value of 115. 7+0.1 eV. The He and Li+ 2p4f "F states decay to ls4f "F states with wavelengths too close to the resonance. transition 2p-+1s of the corresponding one-electron system to be observed in beam-foil experiments. The Li+ 2p4f "F states, however, decay to 2p3d "D states with 2, = 3825.4+0.1 and 4352.2~0.1 A, respectively, and they should be susceptible of experimental observation.