Relativistic many-body calculations of excitation energies, oscillator strengths, transition rates, and lifetimes in samariumlike ions

Abstract

The unique atomic properties of samariumlike ions, not yet measured experimentally, are theoretically predicted and studied in this paper. Excitation energies, oscillator strengths, transition probabilities, and lifetimes are calculated for (5s 2 + 5p 2 + 5d 2 + 5s5d + 5s5g + 5p5f )-(5s5p + 5s5f + 5p5d + 5p5g) electric dipole transitions in Sm-like ions with nuclear charge Z ranging from 74 to 100. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 4f 14 Dirac-Fock potential. First-order perturbation theory is used to obtain intermediate coupling coefficients, and the second-order RMBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order E1 matrix elements to achieve agreement between length-form and velocity-form amplitudes. The resulting transition energies and transition probabilities, and lifetimes for Sm-like W 12+ are compared with results obtained by the relativistic Hartree-Fock approximation (COWAN code) to estimate contributions of the 4f -core-excited states. Trends of excitation energies and oscillator strengths as the function of nuclear charge Z are shown graphically for selected states and transitions. This work provides a number of yet unmeasured atomic properties of these samariumlike ions for various applications and as a benchmark for testing theory.

Tungsten spectroscopy in the EUV range observed at a high-temperature superconducting electron-beam ion trap

“…Moreover, our results are in better agreement with the RMBPT2 results, and most of the excitation energies agree within 2%. We would like to point out that in spite of the fact that the ground state suggested from our calculations is the same as the ones given by Kramida and Shirai's and Safronova et al's works [28,30], this is only a tentative identification. The level splitting of the 4f 12 5s 2 5p 2 configuration is very sensitive to the computational model, and the inclusion of more correlation might push the lowest level in this configuration below the 4f 14 5s 2 1 S0 level.…”

“…We also compared our computational results with available data in [30]. The differences between our RCI results and the various results from [30], i.e., first-order relativistic many-body perturbation theory (RMBPT1), secondorder relativistic many-body perturbation theory (RMBPT2), and COWAN (a Hartree-Fock relativistic method) values of excitation energies, are 1%-5%, 0%-3%, and 1%-4%, respectively. Moreover, our results are in better agreement with the RMBPT2 results, and most of the excitation energies agree within 2%.…”

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

“…Within the frame of the tungsten collisions project reviewed in this communication, processes described by Equations (1)- (5) were studied for selected charge states by experiments which were partially accompanied by theory. In addition to information about the collision processes listed above, cross sections and rate coefficients for charge transfer ( [18,19] and references therein), electron-impact excitation ( [20,21] and references therein) together with spectroscopic information ( [22] and references therein) on tungsten ions in all charge states are needed for plasma diagnostics. Spectroscopic observations and further collisional data are becoming available now and are summarized in several contributions to the present Special Issue of ATOMS on "Atomic Data for Tungsten".…”

Hyperfine induced transition probabilities from $4{f}^{14}5s5p{}^{3}{{\rm{P}}}_{0,2}^{o}$ states in Sm-like ions

“…The 4f 14 5s5p 3 P 0,2 states are not metastable as the 5s5p 3 P 0,2 states in other divalent atomic systems. However, the energy difference between 4f and outmost 5s or 5p orbitals increases with Z, because the 4f shell is more tightly bound for ions with the higher degree of ionization [24]. In Fig.…”

“…Here, we focus on the influence of HITs on lifetimes of the metastable 4f 14 5s5p 3 P 0,2 states in Sm-like ions. The ground state of neutral Sm (Z = 62) is [Kr]4d 10 5s 2 5p 6 4f 6 6s 2 7 F 0 , and the ground states of Sm-like ions change several times with increasing atomic number due to the competition between 4f , 5s, 5p and 6s orbitals, eventually turn into the [Kr]4d 10 4f 14 5s 2 1 S 0 state for W 12+ (Z = 74) and heavier ions [24]. The scheme of the low-lying levels calculated in the Dirac-Hartree-Fock (DHF) approximation for W 12+ are shown in Fig.…”