16 research outputs found
Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: Atoms Hg and Pb and their compounds
A way to account for correlations between the chemically active (valence) and
innermore (core) electrons in the framework of the generalized relativistic
effective core potential (GRECP) method is suggested. The "correlated" GRECP's
(CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the
external twelve and four electrons of them, correspondingly, should be treated
explicitly in the subsequent calculations with these CGRECP's whereas the
innermore electrons are excluded from the calculations. Results of atomic
calculations with the correlated and earlier GRECP versions are compared with
the corresponding all-electron Dirac-Coulomb values. Calculations with the
above GRECP's and CGRECP's are also carried out for the lowest-lying states of
the HgH molecule and its cation and for the ground state of the PbO molecule as
compared to earlier calculations and experimental data. The accuracy for the
vibrational frequencies is increased up to an order of magnitude and the errors
for the bond lengths (rotational constants) are decreased in about two times
when the correlated GRECP's are applied instead of earlier GRECP versions
employing the same innercore-outercore-valence partitioning.Comment: 12 pages, 4 tables, the text of the paper was significantly improve
QED corrections to the parity-nonconserving 6s-7s amplitude in Cs
The complete gauge-invariant set of the one-loop QED corrections to the
parity-nonconserving 6s-7s amplitude in Cs is evaluated to all orders
in using a local version of the Dirac-Hartree-Fock potential. The
calculations are peformed in both length and velocity gauges for the absorbed
photon. The total binding QED correction is found to be -0.27(3)%, which
differs from previous evaluations of this effect. The weak charge of
Cs, derived using two most accurate values of the vector transition
polarizability , is for and for . The first value
deviates by from the prediction of the Standard Model, while the
second one is in perfect agreement with it.Comment: 4 pages, 1 figure, 2 table
Radiative and correlation effects on the parity-nonconserving transition amplitude in heavy alkaline atoms
The complete gauge-invariant set of the one-loop QED corrections to the
parity-nonconserving (PNC) amplitude in cesium and francium is evaluated to all
orders in using a local form of the Dirac-Fock potential. The
calculations are performed in both length and velocity gauges for the absorbed
photon and the total binding QED correction is found to be 0.27(3)% for Cs
and 0.28(5)% for Fr. Moreover, a high-precision calculation of the
electron-correlation and Breit-interaction effects on the 7 PNC amplitude
in francium using a large-scale configuration-interaction Dirac-Fock method is
performed. The obtained results are employed to improve the theoretical
predictions for the PNC transition amplitude in Cs and Fr. Using an average
value from two most accurate measurements of the vector transition
polarizability, the weak charge of Cs is derived to amount to . This value deviates by
from the prediction of the standard model. The values of the - PNC
amplitude in Fr and Fr are obtained to be 15.49(15) and
14.16(14), respectively, in units of i a.u.Comment: 28 pages, 8 tables, 2 figure
Ground-state hyperfine structure of H-, Li-, and B-like ions in middle-Z region
The hyperfine splitting of the ground state of H-, Li-, and B-like ions is
investigated in details within the range of nuclear numbers Z = 7-28. The
rigorous QED approach together with the large-scale configuration-interaction
Dirac-Fock-Sturm method are employed for the evaluation of the
interelectronic-interaction contributions of first and higher orders in 1/Z.
The screened QED corrections are evaluated to all orders in (\alpha Z)
utilizing an effective potential approach. The influence of nuclear
magnetization distribution is taken into account within the single-particle
nuclear model. The specific differences between the hyperfine-structure level
shifts of H- and Li-like ions, where the uncertainties associated with the
nuclear structure corrections are significantly reduced, are also calculated.Comment: 22 pages, 11 tables, 2 figure
Dual kinetic balance approach to basis set expansions for the Dirac equation
A new approach to finite basis sets for the Dirac equation is developed. It
solves the problem of spurious states and, as a result, improves the
convergence properties of basis set calculations. The efficiency of the method
is demonstrated for finite basis sets constructed from B splines by calculating
the one-loop self-energy correction for a hydrogenlike ion.Comment: 14 pages, 1 tabl
Calculation of T_ odd effects in $"" sup 205_TIF including electron correlation
A method and codes for two-step correlation calculation of heavy-atom
molecules have been developed, employing the generalized relativistic effective
core potential and relativistic coupled cluster (RCC) methods at the first
step, followed by nonvariational one-center restoration of proper
four-component spinors in the heavy cores. Electron correlation is included for
the first time in an ab initio calculation of the interaction of the permanent
P,T-odd proton electric dipole moment with the internal electromagnetic field
in a molecule. The calculation is performed for the ground state of TlF at the
experimental equilibrium, R_e=2.0844 A, and at R=2.1 A, with spin-orbit and
correlation effects included by RCC. Calculated results with single cluster
amplitudes only are in good agreement (3% and 1%) with recent
Dirac-Hartree-Fock (DHF) values of the magnetic parameter M; the larger
differences occurring between present and DHF volume parameter (X) values, as
well as between the two DHF calculations, are explained. Inclusion of electron
correlation by GRECP/RCC with single and double excitations has a major effect
on the P,T-odd parameters, decreasing M by 17% and X by 22%.Comment: 5 pages, REVTeX4 style Accepted for publication in Phys.Rev.Letter