Radiative association of P+(3P) and O(3P) for the PO+ formation

Abstract

Phosphorus (P) is essential for the development of life since it is a fundamental element in many important biological molecules. Due to its biogenic importance, many astrochemists have begun to investigate the possibility of the P-bearing species formed in interstellar environments. Radiative association (RA) is a possible way for the formation of the phosphorus monoxide ion (PO+) in interstellar and related environments. Laboratory measurements are almost impossible to carry out, so theoretical calculations are essential for investigating such formation mechanism of PO+. The quantum mechanical method is used to obtain its cross sections and rate coefficients. Thirty contributing processes for the computation of the total rate coefficient are considered, including 22 transition dipole processes and 8 permanent dipole processes. The total rate coefficient varies little over the entire temperature range of 1-10000 K and its magnitude is of the order of (4∼8) × 10−17 cm3·s−1. The 2 1Σ+ →X 1Σ+ transition process dominates the formation of PO+ by RA over the entire temperature range considered here. The C 1Π →X 1Σ+ and 2 3Σ+ →a 3Σ+ are also relatively important, but their rate coefficients are about an order of magnitude smaller than that of the 2 1Σ+ →X 1Σ+ channel. The obtained cross sections and rate coefficient can be used to model the P astrochemistry in the interstellar medium.