Electron impact excitation rates for transitions in Mg V

TL;DR

This paper reports detailed calculations of energy levels, radiative rates, and collision strengths for Mg V, an astrophysically important ion, using advanced computational methods, and compares results with previous data to identify discrepancies.

Contribution

It provides new, comprehensive atomic data for Mg V, including energy levels, radiative rates, and collision strengths, with improved accuracy and resolution of resonances.

Findings

Results generally agree with previous data but show significant discrepancies for many transitions.

Resonance effects are carefully resolved to improve collision strength calculations.

Data covers temperatures up to 10^6 K for astrophysical modeling.

Abstract

Energy levels, radiative rates (A-values) and lifetimes, calculated with the GRASP code, are reported for an astrophysically important O-like ion Mg~V. Results are presented for transitions among the lowest 86 levels belonging to the 2s$^2$2p$^4$, 2s2p$^5$, 2p$^6$, and 2s$^2$2p$^3$3$\ell$ configurations. There is satisfactory agreement with earlier data for most levels/transitions, but scope remains for improvement. Collision strengths are also calculated, with the DARC code, and the results obtained are comparable for most transitions (at energies above thresholds) with earlier work using the DW code. In thresholds region, resonances have been resolved in a fine energy mesh to determine values of effective collision strengths ($\Upsilon$) as accurately as possible. Results are reported for all transitions at temperatures up to 10$^6$~K, which should be sufficient for most astrophysical applications. However, a comparison with earlier data reveals discrepancies of up to two orders of magnitude for over 60\% of transitions, at all temperatures. The reasons for these discrepancies are discussed in detail.