Relativistic and Coulomb autoionisation in low-lying excited states of fluorine

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Abstract
By applying a state-specific many-electron approach to the Breit-Pauli Hamiltonian, the authors have computed the relativistic autoionisation rate of the F 1s22s2p4(1S)3s 2S state whose lifetime was measured recently by the beam-foil technique and found to be tau =0.31+or-0.1*10-9 s. They find Gamma =1.7*109 s-1, which is about three times the theoretical prediction for the radiative transition rate to the ground state. The sum of the two contributions yields tau =0.45*10-9 s. Another Rydberg state F 2s22p4(1D)3d 2P, has a Coulomb autoionisation rate of 4.8*1011 s-1. However, its relativistic mixing with 3s 2S is very small and thus does not affect its lifetime. The present calculation has taken into account the following major effects: relaxation of orbitals of different states, non-orthonormality, electron correlation in initial and final states, core (K-shell)-valence interactions via the two-body spin-orbit operator, valence-valence relativistic interactions and term-dependent continuum orbitals.