Effects of the electron correlation and Breit and hyperfine interactions on the lifetime of the 2p${}^5$3s states in neutral neon

In the framework of the multiconfiguration Dirac-Hartree-Fock method, we investigate the transition properties of four excited states in the $2p^{5}3s$ configuration of neutral neon. The electron correlation effects are taken into account systematically by using the active space approach. The effect of higher-order correlation on fine structures is shown. We also study the influence of the Breit interaction and find that it reduces the oscillator strength of the ${}^3{P}_1^o{-}^1{S}_0$ transition by 17%. It turns out that the inclusion of the Breit interaction is essential even for such a light atomic system. Our ab initio calculated line strengths, oscillator strengths and transition rates are compared with other theoretical values and experimental measurements. Good agreement is found except for the ${}^3{P}_2^o{-}^1{S}_0$ M2 transition for which discrepancies of around 15% between theories and experiments remain. In addition, the impact of hyperfine interactions on the lifetimes of the ${}^3{P}_0^o$ and ${}^3{P}_2^o$ metastable states is investigated for the ${}^{21}$Ne isotope (I=3/2). We find that hyperfine interactions reduce the lifetimes drastically. For the ${}^3{P}_0^o$ state the lifetime is decreased by a factor of 630.