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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]