Biosignature Line Ratios of [P II] in Exoplanetary and Nebular Environments

Being the backbone element of DNA, phosphorus is a key component in the search for life in the Universe. To aid in its detection, we present line emissivity ratios for the five lowest-lying forbidden [P II] transitions among levels 3s²3p² (³P₀, ³P₁, ³P₂, ¹D₂, ¹S₀) within wavelengths range of 0.44-70 µm where several lie within the spectroscopic domain of observation of James Webb Space Telescope. These line ratios have been obtained using a new collisional-radiative-recombination (CRR) model that incorporates a new scheme for the total level-specific (e+ion) recombination rate coefficients from the unified method of Nahar and Pradhan. CRR implements electron impact excitation (EIE) rate coefficients calculated from the accurate Breit-Pauli R-Matrix method. We will report its effect compared to that obtained using only electron impact excitation and spontaneous radiative decay rates. We find that (e + ion) recombination has a significant impact on all line ratios, and represents a major improvement in the physical accuracy of emission line models.