Isotope shift in the electron affinity of lithium (original) (raw)
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The Journal of Chemical Physics, 2007
Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of 7 Li and 7 Li −. The nuclear motion has been explicitly included in the calculations ͑i.e., they have been done without assuming the Born-Oppenheimer ͑BO͒ approximation͒. An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed. This led to a noticeable improvement of the previously determined variational upper bound to the nonrelativistic energy of Li −. The Li energy obtained in the calculations matches those of the most accurate results obtained with Hylleraas functions. The finite-mass ͑non-BO͒ wave functions were used to calculate the ␣ 2 relativistic corrections ͑␣ =1/c͒. With those corrections and the ␣ 3 and ␣ 4 corrections taken from Pachucki and Komasa ͓J. Chem. Phys. 125, 204304 ͑2006͔͒, the electron affinity ͑EA͒ of 7 Li was determined. It agrees very well with the most recent experimental EA.
Relativistic calculations of the isotope shifts in highly charged Li-like ions
Physical Review A, 2014
Relativistic calculations of the isotope shifts of energy levels in highly charged Li-like ions are performed. The nuclear recoil (mass shift) contributions are calculated by merging the perturbative and large-scale configuration-interaction Dirac-Fock-Sturm (CI-DFS) methods. The nuclear size (field shift) contributions are evaluated by the CI-DFS method including the electron-correlation, Breit, and QED corrections. The nuclear deformation and nuclear polarization corrections to the isotope shifts in Li-like neodymium, thorium, and uranium are also considered. The results of the calculations are compared with the theoretical values obtained with other methods. arXiv:1410.7071v1 [physics.atom-ph]
Charge radii and ground state structure of lithium isotopes: Experiment and theory reexamined
Physical Review C, 2011
Changes in the nuclear charge radii of lithium isotopes were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. We discuss the choice of the reference isotope for absolute charge radii determinations in the lithium isotopic chain and report a new value for the charge radius of 6 Li, based on the analysis of the world scattering data. A summary of the lithium nuclear charge radii obtained in this way is presented. Additionally, new calculations in fermionic molecular dynamics for the lithium isotopes were performed. We summarize the status of the lithium nuclear charge radii, magnetic dipole and electric quadrupole moments from experimental investigations and compare them to the results of various microscopic and three-body nuclear models.
Isotope shift in the electron affinity of
2013
The specific mass shift in the electron affinity between 35 Cl and 37 Cl has been determined by tunable laser photodetachment spectroscopy to be −0.51(14) GHz. The isotope shift was observed as a difference in the onset of the photodetachment process for the two isotopes. In addition, the electron affinity of Cl was found to be 29 138.59(22) cm −1 , giving a factor of 2 improvement in the accuracy over earlier measurements. Many-body calculations including lowest-order correlation effects demonstrates the sensitivity of the specific mass shift and show that the inclusion of higherorder correlation effects would be necessary for a quantitative description.
Calculations on theS2ground state of the lithium atom
Physical Review A, 1986
Extensive variational. calculations on the S ground state of the lithium atom are reported. %ith use of a 352-term Hylleraas-type expansion, the nonrelativistic ground-state energy of 5 Lit is determined to be-7.478058 a.u. , which lies approximately 3 cm above empirical estimates of the nonrelativistic ground-state energy. This variational upper bound to the ground-state energy is the lowest to our knowledge reported to date in the literature. A number of expectation values, including the individual energy terms, the Fermi-contact interaction, the electron density at the nucleus, and the moments (rP), n =1-3, and (r;J), n =1,2, are also evaluated. The general rates of convergence of the calculation are discussed. The role played by the two doublet spin eigenfunctions is examined, and the importance of including both of these functions for the accurate calculation of the Fermi-contact interaction is discussed.
CI calculations for ground and the lowest core-excited states of Li and Li−
Physica B-condensed Matter, 2019
Large scale, accurate non-relativistic configuration interaction (CI) calculations for the ground and core excited states of Li (2 S, 4 P°and 4 P) and Li − (1 S, 5 P and 5 S°) corrected for relativistic and mass polarization effects. Priori selected CI and CI by parts techniques are implemented to approximate both the large scale wavefunction and the solution of large CI eigenvalue problem respectively. Systematic studies of energy and electron affinity convergence with respect to CI excitation level are reported. The calculated value of electron affinity of the ground 1 S state is 618.05(5) meV in excellent agreement with experiment. Calculations on excited states reveal more accurate values of the positions of 5 P and 5 S°states of Li − , lying 505.86(5) meV and 291.20(5) meV below 4 P°and 4 P states respectively of Li. Transition energies and wavelength of the electric dipole decay 4 P → 4 P°of Li and 5 S°→ 5 P of Li − , show reasonably good agreement with available theoretical and experimental data.
Relativistic and QED corrections to the g factor of Li-like ions
Physical Review A, 2004
Calculations of various corrections to the g factor of Li-like ions are presented, which result in a significant improvement of the theoretical accuracy in the region Z = 6 -92. The configuration-interaction Dirac-Fock method is employed for the evaluation of the interelectronic-interaction correction of order 1/Z 2 and higher. This correction is combined with the 1/Z interelectronic-interaction term derived within a rigorous QED approach. The one-electron QED corrections of first in α are calculated to all orders in the parameter αZ. The screening of QED corrections is taken into account to the leading orders in αZ and 1/Z.
Relativistic calculations of isotope shifts in highly charged ions
Physical Review A, 2003
Relativistic calculations of the isotope shifts of energy levels in highly charged Li-like ions are performed. The nuclear recoil (mass shift) contributions are calculated by merging the perturbative and large-scale configuration-interaction Dirac-Fock-Sturm (CI-DFS) methods. The nuclear size (field shift) contributions are evaluated by the CI-DFS method including the electron-correlation, Breit, and QED corrections. The nuclear deformation and nuclear polarization corrections to the isotope shifts in Li-like neodymium, thorium, and uranium are also considered. The results of the calculations are compared with the theoretical values obtained with other methods. arXiv:1410.7071v1 [physics.atom-ph]
Accurate calculations for the autoionizing states of the lithium atom
Physics Letters A, 1998
The nonrelativistic energies of the core-excited doublets of the lithium atom are calculated by using a full core plus correlation method. Relativistic and mass-polarization effects on the energy are evaluated as first-order perturbation theory by using the Pauli-Breit operators. In most cases, our results are in close agreement with experiments.
Journal of Chemical Physics, 2019
Attosecond and femtosecond spectroscopies present opportunities for the control of chemical reaction dynamics and products, as well as for quantum information processing; we address the somewhat unique situation of core-ionization spectroscopy which, for dimeric chromophores, leads to strong valence charge localization and hence tightly paired potential-energy surfaces of very similar shape. Application is made to the quantum dynamics of core-ionized Li 2 +. This system is chosen as Li 2 is the simplest stable molecule facilitating both core ionization and valence ionization. First, the quantum dynamics of some model surfaces are considered, with the surprising result that subtle differences in shape between core-ionization paired surfaces can lead to dramatic differences in the interplay between electronic charge migration and charge transfer induced by nuclear motion. Then, equation-of-motion coupled-cluster calculations are applied to determine potential-energy surfaces for 8 core-excited state pairs, calculations believed to be the first of their type for other than the lowest-energy core-ionized molecular pair. While known results for the lowest-energy pair suggest that Li 2 + is unsuitable for studying charge migration, higher-energy pairs are predicted to yield results showing competition between charge migration and charge transfer. Central is a focus on the application of Hush's 1975 theory for core-ionized X-ray photoelectron spectroscopy to understand the shapes of the potential-energy surfaces and hence predict key features of charge migration.