Theoretical Atomic Collisions Laboratory

Three P-wave resonances in positron–lithium system below the Ps (n=2) threshold are calculated using the stabilization method. A model potential is used to represent the interaction between the core and the outermost active electron. Hylleraas-type wave functions are used to represent the correlation effects between the outer electron, the positron and the core. Our results are compared with those in the literature.

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We have made a first investigation on the resonances in two electron systems in various model plasma environments. The 2s2 1Se autoionization resonance state in the helium atom is determined by calculating the density of resonance states using the stabilization method. A screened Coulomb potential obtained from the Debye model is used to represent the interaction between the charged particles. A correlated wave function has been used to represent the correlation effect between the three charge particles. The calculated resonance energies and widths for various Debye parameters ranging from infinity to a small value along with the ground state energies are reported.

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We have investigated the doubly excited 1,3 P o resonance states of helium embedded in weakly coupled plasmas. A screened Coulomb potential obtained from the Debye model is used to represent the interaction between the charge particles. A correlated wavefunction consisting of a generalized exponential expansion has been used to represent the correlation effect. A total of 18 resonances (9 each for 1 P o and 3 P o states) below the n = 2 He + thresholds has been estimated by calculating the density of states using a stabilization method. For each spin state, this includes four members in the 2s n p + (2 ≤ n ≤ 5) series, three members in the 2s n p − (3 ≤ n ≤ 5) series, and two members from 2p n d( n = 3, 4) series. The resonance energies and widths for various Debye parameters ranging from infinity to a small value for these 1,3 P o resonance states are reported. In addition, the wavelengths for the photo-absorption of a helium atom from its ground state to such 1 P o resonance states for different Debye lengths are also reported.

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