Determination of quantum defects from the poles of the Schwinger T matrix
Quantum defects are determined for lithium, sodium, potassium, and beryllium by searching for the poles of the Schwinger T matrix along the negative real-energy axis. This method takes advantage of the fundamental ideas of QDT by using a Coulomb Green's function to factor out most of the energy dependence. For the alkali atoms, a single-channel calculation is performed using model potentials to include the effects of core polarization and correlation. Quantum defects accurate to 1% are easily obtained with small grids and small fixed-basis sets for an entire Rydberg series up to principal quantum number, n, as high as 60. A multichannel extension of this method is used to determined neutral-beryllium quantum defects for the /sup 1/P/sup 0/, /sup 3/P/sup 0/, and /sup 3/S Rydberg series. The /sup 1/P/sup 0/ and /sup 3/P/sup 0/ calculations are performed in a two-channel approximation using 1s/sup 2/2p static-exchange cores. The /sup 3/S calculation includes a third channel with a 1s/sup 2/3s core. Accurate quantum defects are obtained with 4 to 6 basis functions per channel. The energies are variational and the wave functions have the correct asymptotic form enforced by the Coulomb Green's function. Tentative results for Be I /sup 1/P/sup 0/ and /sup 3/P/sup 0/ resonances below the 1s/sup 2/2p/sup 2/P threshold are presented. This calculation which is performed in a three-channel approximation uses a complex multichannel Coulomb Green's function to search for poles in the fourth quadrant of the complex-energy plane.
- Research Organization:
- Oklahoma Univ., Norman (USA)
- OSTI ID:
- 7058898
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BERYLLIUM
RYDBERG STATES
LITHIUM
POTASSIUM
S MATRIX
SCHWINGER TERMS
SODIUM
GREEN FUNCTION
UNITARY POLE APPROXIMATION
ALKALI METALS
ALKALINE EARTH METALS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
FUNCTIONS
MATRICES
METALS
640302* - Atomic
Molecular & Chemical Physics- Atomic & Molecular Properties & Theory
645400 - High Energy Physics- Field Theory