  The most important processes for the creation of S12+ to S14+ ions excited
states from the ground configurations of S9+ to S14+ ions in an electron
cyclotron resonance ion source, leading to the emission of K X-ray lines, are
studied. Theoretical values for inner-shell excitation and ionization cross
sections, including double KL and triple KLL ionization, transition
probabilities and energies for the deexcitation processes, are calculated in
the framework of the multi-configuration Dirac-Fock method. With reasonable
assumptions about the electron energy distribution, a theoretical K$\alpha$
X-ray spectrum is obtained, which is compared to recent experimental data.
