The Iron Project: R-matrix collision strengths and line emissivity ratios for Fe-peak elements - Mn III

The Iron Project is focused on R-matrix close coupling calculations for

Fe-peak elements for astrophysical and laboratory applications.

An outstanding feature of these high-accuracy computations is the

extensive autoionizing resonance structures that manifest themselves in

atomic processes. For electron impact excitation resonances in collision

strengths result in considerable enhancement of Maxwellian averaged 

collision strengths or rate coefficients specific at temperatures.

Manganese is an important element in cosmological evolution of the

universe as it is produced in supernovae Type Ia together with Fe in 

binary explosions of white dwarfs which form from low mass stars over 

long timescales of Gyrs. However, Fe is also produced in massive star core collapse Type II 

supernovae that happen on much shorter timescales of Myrs. Therefore, the 

abundance ratio Mn/Fe is a chronometer of galaxy evolution, nucleosynthesis 

and star formation. In this work relativistic Breit-Pauli R-matrix calculations have been 

carried out for electron impact excitation (EIE) of doubly ionized Manganese

that has not been previously studied. 

The coupled channel calculations include a wavefunction that includes 38 

excited levels of Mn III dominated by electronic configurations 3d⁵ and

3d⁴4s, and 33 bound channel configurations of Mn II for additional correlation.

EIE collision strength for forbidden transitions among those levels are studied. Their emissivity

line ratios are computed using computed collision strengths and radiative

decay A-values. Based on this work, certain lines of Mn III are predicted to be useful

temperature-density diagnostics, as well as determinant of cosmic Mn abundance.