218 research outputs found
Forbidden M1 and E2 transitions in monovalent atoms and ions
We carried out a systematic high-precision relativistic study of the
forbidden magnetic-dipole and electric-quadrupole transitions in Ca+, Rb, Sr+,
Cs, Ba+, Fr, Ra+, Ac2+, and Th3+. This work is motivated by the importance of
these transitions for tests of fundamental physics and precision measurements.
The relative importance of the relativistic, correlation, Breit correction, and
contributions of negative-energy states is investigated. Recommended values of
reduced matrix elements are presented together with their uncertainties. The
matrix elements and resulting lifetimes are compared with other theoretical
values and with experiment where available.Comment: 9 pages, 6 table
Relativistic many-body calculation of energies, lifetimes, polarizabilities, blackbody radiative shift and hyperfine constants in Lu2+
Energy levels of 30 low-lying states of Lu2+ and allowed electric-dipole
matrix elements between these states are evaluated using a relativistic
all-order method in which all single, double and partial triple excitations of
Dirac-Fock wave functions are included to all orders of perturbation theory.
Matrix elements are critically evaluated for their accuracy and recommended
values of the matrix elements are given together with uncertainty estimates.
Line strengths, transition rates and lifetimes of the metastable 5d(3/2) and
5d(5/2) states are calculated. Recommended values are given for static
polarizabilities of the 6s, 5d and 6p states and tensor polarizabilities of the
5d and 6p(3/2) states. Uncertainties of the polarizability values are estimated
in all cases. The blackbody radiation shift of the 6s(1/2)-5d(5/2) transition
frequency of the Lu2+ ion is calculated with the aid of the recommended scalar
polarizabilities of the 6s(1/2) and 5d(5/2) states. Finally, A and B hyperfine
constants are determined for states of 175Lu2+ with n <= 9. This work provides
recommended values of transition matrix elements, polarizabilities and
hyperfine constants of Lu2+, critically evaluated for accuracy, for benchmark
tests of high-precision theoretical methodology and planning of future
experiments.Comment: 9 pages, 10 table
Magic wavelengths for optical cooling and trapping of lithium
Using first-principles calculations, we identify magic wavelengths for the
2s-2p and 2s-3p transitions in lithium. The ns and np atomic levels have the
same ac Stark shifts at the corresponding magic wavelength, which facilitates
state-insensitive optical cooling and trapping. Tune-out wavelengths for which
the ground-state frequency-dependent polarizability vanishes are also
calculated. Differences of these wavelengths between 6Li and 7Li are reported.
Our approach uses high-precision, relativistic all-order methods in which all
single, double, and partial triple excitations of the Dirac-Fock wave functions
are included to all orders of perturbation theory. Recommended values are
provided for a large number of Li electric-dipole matrix elements. Static
polarizabilities for the 2s, 2p, 3s, 3p, and 3d levels are compared with other
theory and experiment where available. Uncertainties of all recommended values
are estimated. The magic wavelengths for the uv 2s-3p transition are of
particular interest for the production of a quantum gas of lithium [Duarte et
al., Phys. Rev. A 84, 061406R (2011)].Comment: 7 pages, 5 figure
Transitions between the -core-excited states in Ir, Ir, and Ir ions for clock applications
Iridium ions near - level crossings are the leading candidates for a
new type of atomic clocks with a high projected accuracy and a very high
sensitivity to the temporal variation of the fine structure constant .
To identify spectra of these ions in experiment accurate calculations of the
spectra and electromagnetic transition probabilities should be performed.
Properties of the -core-excited states in Ir, Ir, and
Ir ions are evaluated using relativistic many-body perturbation theory
and Hartree-Fock-Relativistic method (COWAN code). We evaluate excitation
energies, wavelengths, oscillator strengths, and transition rates. Our
large-scale calculations includes the following set of configurations:
with equal to 3, 2, and 1 for the Ir,
Ir, and Ir ions, respectively. The transitions are
illustrated by the synthetic spectra in the 180 - 200 \AA range. Large
contributions of magnetic-dipole transitions to lifetimes of low-lying states
in the region below 2.5 Ry are demonstrated.Comment: 10 page
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