Relativistic calculations of transition amplitudes in the helium isoelectronic sequence [Book Chapter]
- Univ. of Notre Dame, IN (United States)
The helium atom and helium-like ions occupy a special position in atomic physics as the simplest multielectron systems. Unlike atoms and ions with many electrons, the fact that only two electrons are present allows calculations of extremely high accuracy to be carried out in the nonrelativistic case. At low Z, the leading relativistic and QED corrections can be calculated as perturbations. However, at higher Z it is desirable to start from a completely relativistic formalism. A well-known problem of any such formalism is the correct treatment of negative-energy states, which, if included improperly, lead to the continuum dissolution problem discussed by Sucher. This problem can be avoided by using the no-pair Hamiltonian, which excludes negative-energy states. Configuration interaction (CI) techniques were used to carry out accurate calculations of energies of n = 1 and n = 2 states along the helium isoelectronic sequence, starting from the no-pair Hamiltonian. Similar calculations were carried out in using interactive techniques. It is the purpose of this chapter to extend these calculations to evaluate transition amplitudes along the helium isoelectronic sequence. Specifically, we present highly accurate theoretical calculations of single-photon transition amplitudes and transition rates for 2-2 and 2-1 transitions in helium-like ions with charges in the range Z = 2-100. Amplitudes for the electric-dipole (E{sub 1}) transitions 2{sup 1}P{sub 1} {r_arrow} 1 {sup 1}S{sub o}, 2{sup 1}P{sub 1} {r_arrow} 2{sup 1}S{sub o}, 2{sup 3}P{sub o,1,2} {r_arrow} 2{sup 3}S{sub 1}, w{sup 1}P{sub 1} {r_arrow}, and 2{sup 3}P{sub 1} {r_arrow} 1{sup 1}S{sub o} are calculated in length form and in velocity form. Amplitudes for the magnetic-dipole M{sub 1} transitions 2{sup 3}S{sub 1}{r_arrow} 1 {sup 1}S{sub o} and the magnetic-quadrupole (M{sub 2}) transitions 2{sup 3}P{sub 2} {r_arrow} 1 {sup 1}S{sub o} are evaluated in velocity form. 78 refs., 5 figs., 16 tabs.
- Research Organization:
- Univ. of Notre Dame, IN (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 443541
- Resource Relation:
- Other Information: PBD: 1995; Related Information: Advances In Atomic, Molecular, and Optical Physics, Volume 35, 1995, Pages 255–329
- Country of Publication:
- United States
- Language:
- English
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