2016MNRAS.457.3096A

The formation of PO from the radiative association of phosphorus and oxygen atoms has been estimated by accurate quantum chemistry calculations. The radiative association of P and O atoms along the B²Σ⁺ potential energy curve is the most efficient way of producing PO in the X²Π ground state. For temperatures ranging between 300 and 14 000 K, the rate coefficients are found to vary from 1.61 x 10^–24 to 1.99 x 10^–18 cm³/s, respectively. These values indicate that only a very small amount of PO molecules can be formed by radiative association in dense and hot gas close to the photosphere of evolved oxygen-rich stars and other hostile environments.