Abstract
The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient describing the interaction of metastable atomic hydrogen ( state) with a ground-state hydrogen atom is resolved. In the the van der Waals range , where is the Bohr radius and is the fine-structure constant, one finds the symmetry-dependent result ( denotes the Hartree energy). In the Casimir-Polder range , where is the Lamb shift energy, one finds . In the the Lamb shift range , we find an oscillatory tail with a negligible interaction energy below . Dirac- perturbations to the interaction are also evaluated and results are given for all asymptotic distance ranges; these effects describe the hyperfine modification of the interaction or, expressed differently, the shift of the hydrogen hyperfine frequency due to interactions with neighboring atoms. The hyperfine frequency has recently been measured very accurately in atomic beam experiments.
- Received 26 September 2016
DOI:https://doi.org/10.1103/PhysRevA.95.022703
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