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We present high-accuracy calculations of radiative properties such as oscillator strengths and transition probabilities, of the allowed ns ²S1/2 → np ²P1/2, 3/2 transitions and of the forbidden np ²P1/2 → np ²P3/2 transitions in the F- and Cl-like alkali and alkaline-earth ions with the ground state principal quantum number n of the respective ion. For this purpose, we have employed the Dirac–Fock, relativistic second-order many-body perturbation theory and an all-order perturbative relativistic method in the coupled-cluster (CC) theory framework. To test the validity of these methods for giving accurate results, we first evaluated the ionization potentials in the creation processes of these ions and compare them with their experimental values listed in the National Institute of Science and Technology data base. Moreover, both the allowed and forbidden transition amplitudes are estimated using the above three methods and a comparative analysis is made to follow-up the electron correlation trends in order to demonstrate the need of using a sophisticated method like the CC theory for their precise determination. For astrophysical use, we provide the most precise values of the transition properties by combining the experimental energies, which suppresses uncertainties from the calculated energies, using the transition amplitudes from the CC method. These data will be useful in the abundance analysis of the considered ions in the astronomical objects and for the diagnostic processes of astrophysical plasmas. [ABSTRACT FROM AUTHOR]

High-accuracy calculations of the forbidden transition amplitudes for the np 2P1/2 →np 2P3/2 transitions with the ground-state principal quantum number n in singly charged inert gas atoms, which are of astrophysical interest, have been carried out using sophisticated relativistic manybody methods. Using these amplitudes, the line strengths, oscillator strengths and transition probabilities of the above transitions and lifetimes of the np 2P1/2 states are estimated precisely. Most of these transition wavelengths lie in the infrared region, while the corresponding Rn II line is the optical one, and they can be observed in the stellar and interstellar media, where the abundances of these ions have already been identified. The above forbidden transitions can also be very useful for astrophysical plasma diagnostics and can guide experiments to measure the lifetimes of the above np 2P1/2 states. [ABSTRACT FROM AUTHOR]

We have carried out calculations of the relativistic sensitivity coefficients, oscillator strengths, transition probabilities, lifetimes and magnetic dipole hyperfine structure constants for a number of low-lying states in the Zn ii, Si iv and Ti ivions which are abundant in the distant quasars and various stellar plasmas. These spectroscopic data will be very useful for probing temporal variation of the fine structure constant (αe) and in the diagnostic processes of some of the astrophysical plasmas. We have employed all-order perturbative methods in the relativistic coupled-cluster framework using the Dirac–Coulomb Hamiltonian to calculate the atomic wavefunctions of the considered ions. Reference states are constructed with the VN−1 and VN+1 potentials and then the electron–electron correlation effects are taken into account by constructing all possible singly and doubly excited configurations, involving both the core and valence electrons, from the respective reference states. We have also determined one electron affinities and ionization potentials of many excited states in these Zn ii, Si ivand Ti iv ions. Except for a few states we have attained accuracies within 1 per cent for the energies compared with their experimental values. Our calculated sensitivity coefficients are estimated to have similar accuracies as of the calculated energies. Furthermore, combining our calculated transition matrix elements with the experimental wavelengths we evaluate transition probabilities, oscillator strengths and lifetimes of some of the excited states in these ions. These results are compared with the available data in a few cases and found to be in very good agreement among themselves. Using our reported hyperfine structure constants due to the dominant magnetic dipole interaction, it is possible to determine hyperfine splittings approximately in the above considered ions. [ABSTRACT FROM AUTHOR]

Aims. We intend to provide accurate data for the oscillator strengths, transition probabilities, lifetimes, and hyperfine shifts of the atomic energy levels in the fluorine (F)- like Ti, V, Cr, Mn, Co, Ni, Cu, Zn, and Mo ions for the diagnostic of the astrophysical plasma. Furthermore, we propose these ions for probing possible variation in the fine structure constant (αe) by observing their transition lines from the distant astronomical objects. Methods. We have employed an all-order perturbative method in the relativistic coupled-cluster framework using the Dirac-Coulomb Hamiltonian for calculating the atomic wave functions in the considered F-like ions.We adopted the Fock-space formalism to account for the correlation effects among the occupied electrons by allowing all possible singly and doubly excited configurations in two steps: first considering the correlations between the electrons in a closed-shell configuration, and second constructing the openshell configurations of the first three low-lying states in the considered atomic systems by removing the respective electron from the core orbitals. This procedure enormously simplifies the computational complexity and overcomes the need to select important configuration state functions in determining the atomic state functions in contrast to a truncated configuration interaction method. Moreover, corrections from the frequency-independent Breit interaction and the lowest order quantum electrodynamic effects are incorporated self-consistently. Results. We present the calculated ionization potential energies of the electrons that are detached to form the above considered F-like ions. The correctness of our estimated results are ensured by comparing them with the available experimental values and other calculations. From these calculations, we evaluate the relativistic sensitivity coefficients that we propose here to be used for probing possible temporal variation of the fine structure constant (αe) through the precise astrophysical observation of the spectral lines of the transitions involving the above low-lying states. The accuracies of these sensitivity coefficients are appraised from the comparison of our calculated energies with the experimental values. We also present the line strengths by calculating the reduced matrix elements of the allowed transitions and of the M1 and E2 forbidden transitions. By combining our calculated line strengths with the observed wavelengths, we determine the oscillator strengths, transition probabilities, and lifetimes of the first two excited states of the above ions and compare them with the other theoretical calculations. The hyperfine splittings of the states are also presented by calculating their magnetic dipole and electric quadrupole hyperfine structure constants. [ABSTRACT FROM AUTHOR]