Electric-dipole, electric-quadrupole, magnetic-dipole, and magnetic-quadrupole transitions in the neon isoelectronic sequence

Excitation energies for $2l-{3l}^{\prime }$ hole-particle states of Ne-like ions are determined to second order in relativistic many-body perturbation theory (MBPT). Reduced matrix elements, line strengths, and transition rates are calculated for electric-dipole $\mathrm{}\left(E1\mathrm{}\right),$ magnetic-quadrupole $\mathrm{}\left(E2\mathrm{}\right),$ magnetic-dipole $\mathrm{}\left(M1\mathrm{}\right),$ and magnetic-quadrupole $\mathrm{}\left(M2\mathrm{}\right)\mathrm{}$ transitions in Ne-like ions with nuclear charges ranging from $Z=11\mathrm{}$ to 100. The calculations start from a ${1s}^2{2s}^2{2p}^6$ closed-shell Dirac-Fock potential and include second-order Coulomb and Breit-Coulomb interactions. First-order many-body perturbation theory (MBPT) is used to obtain intermediate-coupling coefficients, and second-order MBPT is used to determine the matrix elements. Contributions from negative-energy states are included in the second-order $E1,$ $M1,$ $E2,$ and $M2\mathrm{}$ matrix elements. The resulting transition energies are compared with experimental values and with results from other recent calculations. Trends of $E1,$ $E2,$ $M1,$ and $M2\mathrm{}$ transition rates as functions of nuclear charge Z are shown graphically for all transitions to the ground state.