45th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 59, Number 8
Monday–Friday, June 2–6, 2014;
Madison, Wisconsin
Session C8: Invited Session: Advances in Atomic Spectroscopy
2:00 PM–4:00 PM,
Tuesday, June 3, 2014
Room: Hall GJ
Chair: Marianna Safronova, University of Delaware
Abstract ID: BAPS.2014.DAMOP.C8.3
Abstract: C8.00003 : Positive Ion Properties from Spectroscopy of High-L Rydberg levels with the RESIS Method*
3:00 PM–3:30 PM
Preview Abstract
Abstract
Author:
Stephen Lundeen
(Colorado State University)
All atoms and ions have many singly-excited levels with large values of
angular momentum (L \textgreater 5). The existence of these nearly
hydrogenic levels plays an important role in dynamic processes, but the
details of their binding energies are often ignored since they correspond to
very small quantum defects ($\delta $ \textless 0.001) and are very
difficult to observe with standard spectroscopic methods. One very general
method that has been developed specifically to explore the spectroscopy of
these high-L levels is the RESIS, or Resonant Excitation Stark Ionization
Spectroscopy method. With this technique, high-L Rydberg levels formed by
charge capture in a fast atom or ion beam are resonantly excited upwards by
a laser, and the upper level so populated is then Stark Ionized and the
resulting ion collected with high efficiency. Because the laser transition
is upwards, selection rules do not limit the angular momentum of detected
levels, and many different high-L levels can be detected, resolved by the
small differences between their excitation energies and the hydrogenic
transition energy. Once selectively detected in this way, RF/Optical double
resonance methods can measure the binding energy differences between
adjacent levels with high precision. The binding energies of these high-L
levels are a sensitive indicator of many properties of the positive ion
binding them, such as polarizabilites and permanent electric moments. Since
these properties are otherwise difficult to measure and can be difficult to
calculate with confidence, the information derived from RESIS spectroscopy
can provide tests of advanced theoretical methods and input to applications
involving long-range interactions of atoms or ions. Two recent studies
illustrate the method. One determined the dipole and quadrupole
polarizabilities of the Rn-like Th$^{4+}$ ion by measuring the
binding energy differences between n$=$37 Rydberg levels of
Th$^{3+}$ with L$=$8-15 [1]. Another determined the quadrupole and
hexadecapole moments and dipole and quadrupole polarizabilities of the
Fr-like Th$^{3+}$ ion by mapping out the complex pattern of binding
energies of n$=$28 Rydberg levels of Th$^{2+}$ with L$=$9-12 [2].
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[1] Julie A. Keele, Chris. S. Smith, and S.R. Lundeen, Phys. Rev. A
\textbf{85}, 064502 (2012)\\[0pt]
[2] Julie A. Keele, Chris S. Smith, and S.R. Lundeen, Phys. Rev. A
\textbf{88}, 022502 (2013)
*Supported by the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Science, U.S. Department of Energy.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DAMOP.C8.3