THEORY OF MOLECULAR-ORBITAL AND COMPOUND-NUCLEUS X-RAY-EMISSION IN HEAVY-ION-ATOM COLLISIONS WITH NUCLEAR STICKING

Calculations are made of x-ray emission in head-on 200-MeV (lab) Ni+Ni and 860-MeV (lab) Yb+Yb collisions for various values of the compound nucleus lifetime τ. The K x-ray emission probability is obtained by coherently summing the amplitude for a molecular-orbital x-ray transition from the 2 pσ, 2 pπ, 3 pσ, or 3 pπ to the 1 sσ molecular orbital with the amplitude for a compound-nucleus x-ray transition from the united-atom 2 p or 3 p levels to the 1 s level while the projectile and target nuclei stick. If ωKατ {Mathematical expression}1, where ωKατ is the united-atom transition frequency, only molecular orbital x-rays are observed. If ωKατ {Mathematical expression} 1, compound nucleus x-rays are observed. Independent of the projectile velocity, the atomic number of the combined system, and the mechanism for the creation of the 1 sσ vacancy, the compound-nucleus x-rays become sufficiently sharp at ωKατ ≈ 20 to permit the measurement of the united-atom Kα and Kβ x-ray energies to an accuracy of <±5%. The lifetime of the compound nucleus may be sufficiently long to observe K x-rays of 100≲Zu≲140 in fusion-fission nuclear reactions. © 1979 Springer-Verlag.