K-vacancy production in symmetric heavy-ion collisions

Recent calculations of Thorson and co-workers for ${\mathrm{H}}^{+}$ + H ionization mechanisms and the Briggs-Macek scaling law for $K$-vacancy production in symmetric heavy-ion collisions are used to show the following: (1) If Fano-Lichten-type electron promotion is inhibited because of the absence of a $2p$ vacancy, i.e., if $Z>\mathrm{}10\mathrm{}$, $K$ vacancies in symmetric collisions are produced mainly by $2p\sigma$ electron excitation to vacant bound and unbound molecular-orbital states. (2) The direct $1s\sigma$ excitation cross section to vacant bound and unbound states can be obtained experimentally. The relationship between atomic and molecular-orbital Coulomb excitation cross sections is discussed.