Multichannel quantum-defect theory of perturbed Rydberg atoms in external fields

Journal Article · Tue Nov 01 04:00:00 EST 1983 · Phys. Rev. A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.28.2623· OSTI ID:5377068

Lu, K T; Rau, A R.P.

The diamagnetic and Stark shifts of strongly perturbed Rydberg spectra such as those of the alkaline earths are expressed in terms of multichannel--quantum-defect parameters. The theory is applicable when the shifts produced by the external fields are smaller than the neighboring Rydberg separations. It is applied to evaluate the diamagnetic shifts in Ba, an atom in which Rydberg and doubly excited channels are strongly mixed. In such complex spectra, the diamagnetic effect can serve a useful purpose as a tool to disentangle the interacting series. The radial sizes and, therefore, the diamagnetic shifts are quite different for singly and doubly excited states even when they are at the same energy. In fact, for the field strengths considered (approx. =40 kG), the diamagnetic contribution of the doubly excited configuration is quite negligible. As a result, the observed shift is a direct measure of the amount of singly excited configuration in the state of interest. Exactly similar conclusions apply to Stark shifts. The last part of this paper considers states of very high excitation further up in the spectrum which are no longer in a perturbative regime. Spectra of atoms in a magnetic field have shown equally spaced resonances near the ionization threshold with characteristic spacings. By the consideration of the effects of electric fields which are also often simultaneously present, a criterion is established for the nature of these spacings depending on the relative strengths of the crossed electric and magnetic fields. The spacing seen in any particular experiment is shown to depend on the mass and quantum defect of the atom, the strengths of the external fields, and experimental conditions such as the temperature of the atomic vapor whose absorption spectrum is being studied.

• Research Organization: Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5377068
• Journal Information: Phys. Rev. A; (United States), Journal Name: Phys. Rev. A; (United States) Vol. 28:5; ISSN PLRAA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ALKALINE EARTH METALS
BARIUM
CROSSED FIELDS
DIAMAGNETISM
ELEMENTS
ENERGY
ENERGY LEVELS
EXCITED STATES
IONIZATION
MAGNETIC FIELDS
MAGNETISM
METALS
RYDBERG STATES
SPECTRAL RESPONSE
STARK EFFECT
THRESHOLD ENERGY