Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpectroscopic LSJ notation for atomic levels obtained from relativistic calculations
98
0
0.0
(
0
)
Added by
Gaigalas Gediminas Habil. dr.
Publication date
2004
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Today, relativistic calculations are known to provide a very successful means in the study of open-shell atoms and ions. But although accurate atomic data are obtained from these computations, they are traditionally carried out in jj-coupling and, hence, do often not allow for a simple LSJ classification of the atomic levels as needed by experiment. In fact, this lack of providing a proper spectroscopic notation from relativistic structure calculations has recently hampered not only the spectroscopy of medium and heavy elements, but also the interpretation and analysis of inner-shell processes, for which the occurrence of additional vacancies usually leads to a very detailed fine structure. Therefore, in order to facilitate the classification of atomic levels from such computations, here we present a program (within the Ratip environment) which help transform the atomic wave functions from jj-coupled multiconfiguration Dirac-Fock computations into a LS-coupled representation. Beside of a proper LSJ assignment to the atomic levels, the program also supports the full transformation of the wave functions if required for (nonrelativistic) computations.
rate research
Read More
This work establishes a high-precision relativistic theoretical model: start from studying finite speed of light effect based on a coordinate transformation, and further extend the research methods to analyze the overall relativistic effects. This model promotes the development of testing General Relativity with atomic interferometry.
Using the multiconfiguration Dirac-Hartree-Fock and the relativistic configuration interaction methods, a consistent set of transition energies and radiative transition data for the main states of the $2s^2 2p^4$, $2s 2p^5$, $2p^6$, $2s^2 2p^3 3s$, $2s^2 2p^3 3p$, $2s^2 2p^3 3d$, $2s 2p^4 3s$, $2s 2p^4 3p$, and $2s 2p^4 3d$ configurations in O-like Ions between Ar XI ($Z = 18$) and Cr XVII ($Z = 24$) is provided. Our data set is compared with the NIST compiled values and previous calculations. The data are accurate enough for identification and deblending of new emission lines from hot astrophysical and laboratory plasmas. The amount of data of high accuracy is significantly increased for the $n = 3$ states of several O-like ions, where experimental data are very scarce.
This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d8 4d levels of astrophysical interest in singly ionized nickel. Radiative lifetimes of seven high-lying levels of even parity in Ni II (98400 -100600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects. A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194 - 520 nm depopulating even parity 3d8 4d levels. The new calculated gf-values are, on the average, about 20 % higher than a previous calculation by Kurucz (http://kurucz.harvard.edu) and yield lifetimes within 5 % of the experimental values.
The thermal friction force acting on an atom moving relative to a thermal photon bath is known to be proportional to an integral over the imaginary part of the frequency-dependent atomic (dipole) polarizability. Using a numerical approach, we find that blackbody friction on atoms either in dilute environments or in hot ovens is larger than previously thought by orders of magnitude. This enhancement is due to far off-resonant driving of transitions by low-frequency thermal radiation. At typical temperatures, the blackbody radiation maximum lies far below the atomic transition wavelengths. Surprisingly, due to the finite lifetime of atomic levels, which gives rise to Lorentzian line profiles, far off-resonant excitation leads to the dominant contribution to the blackbody friction.
We continue the analysis of quantum two-particle bound systems we have started in (Kholmetskii, A.L., Missevitch, O.V. and Yarman, T. Phys. Scr., 82 (2010), 045301), where we re-postulated the Dirac equation for the bound electron in an external EM field based on the requirement of total momentum conservation, when its EM radiation is prohibited. It has been shown that the modified expression for the energy levels of hydrogenic atoms within such a pure bound field theory (PBFT) provides the same gross and fine structure of energy levels like the standard theory. Now we apply the PBFT to the analysis of hyperfine interactions and show the appearance of some important corrections to the energy levels (the 1S-2S interval and hyperfine spin-spin splitting in positronium, 1S and 2S-2P Lamb shift in hydrogen), which remedies considerably the discrepancy between theoretical predictions and experimental results. In particular, the corrected 1S-2S interval and the spin-spin splitting in positronium practically eliminate the available up to date deviation between theoretical and experimental data. The re-estimated classic 2S-2P Lamb shift as well as ground state Lamb shift in the hydrogen atom lead to the proton charge radius rp=0.837(8) fm (from 2S-2P Lamb shift), and rp=0.840(24) fm (from 1S Lamb shift), which corresponds to the latest estimation of proton size via the measurement of 2S-2P Lamb shift in muonic hydrogen, i.e. rp=0.84184(67) fm. We also emphasize the universal character of PBFT, which is applicable to heavy atoms, too, and analyze 2S-2P interval in Li-like uranium. We show that the corrections we introduced provide a better correspondence between the calculated and experimental data than that furnished by the standard approach. The results obtained support our principal idea of the enhancement of the bound EM field in the absence of EM radiation for quantum bound systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
