Photoionization and Recombination of Astrophysically Important ION Cl II

Photoionization of Cl II $\rightarrow$ e + Cl III is of importance in nebular models since it determines the fractional abundance of [Cl III]. Intensity ratios of collisionally excited forbidden [Cl III] lines are electron density diagnostics, analogous to the prominent [S II] lines. I will present extensive relativistic calculations using Breit-Pauli R-Matrix (BPRM) method aimed at obtaining photoionization cross section up to high energies, and unified recombination cross sections including radiative and di-electronic components (RR and DR). The configuration interaction expansion of the target wavefunctions comprise of $3s^22p^3$, $3s3p^4$, $3s^23p^23d$, $3s^23p^24s$, $3s^23p^24p$, $3s^23p^24d$, $3s^23p^25s$, $3p^33d$, $3s^23p3d^2$, $3p^5$. The preliminary photoionization cross sections of the 8 lowest levels, $3s^23p^4(^3P_{0,1,2},^1D_2, ^1S_0$, $3s3p^3(^3P_{0,1,2}$ of Cl II are compared with the existing measured values at ALS and found to reproduce all features in the observed spectrum.