Perturbative, R-matrix, and MCHF treatments for near-threshold dielectronic recombination of Si-like ions

We present results from a variety of dielectronic recombination (DR) calculations for Si-like ions. A perturbative, multi-configurational Breit-Pauli method is used to calculate DR rate coefficients for the entire Si-like isoelectronic sequence. In addition, we have performed R-matrix and multi-configuration Hartree-Fock (MCHF) calculations to investigate the low-lying resonances that dominate the low-energy, near-threshold region in S$^{2+}$. This work is motivated by the astrophysical importance of DR of Si-like S$^{2+}$ in determining the sulfur ionization balance in the Orion nebula, a photoionized plasma corresponding to low-energy electrons. The computed DR rate coefficients comprise part of the assembly of the DR data base required in the modeling of dynamic finite density plasmas.