J. D. Molitoris

K-vacancy production in high-energy U+U and U+Pb collisions at small impact parameters

Projectile and targetK-vacancy production probabilities in 4.6-, 5.8- and 7.3-MeV/a.m.u. U+U and U+Pb collisions are reported for impact parameters between 10 and 85 fm. These probability measurements are compared with available theory.

Compound elastic cross sections in the isobaric analog resonances 88Sr(p,p0) at 5.06 MeV and 86Sr(p,p0) at 6.02 MeV

We have measured the K-shell ionization probability PK across the isobaric analog resonances in the elastic channel of the reactions 88Sr(p,p0)88Sr at 5.06 MeV and 86Sr(p,p0)86Sr at 6.02 MeV. The dependence of PK on the beam energy for two scattering angles 90° and 155° is analysed in the framework of the theory developed by Anholt et al. taking into account the effect of compound-nucleus scattering. A compound elastic cross section (dσdω)CE = 40 ± 10 mb/sr at the peak of the resonance is deduced in the reaction 88Sr + p at 5.06 MeV, while the experimental results agree with a negligible value of (dσdω)CE for the resonance in 86Sr + p at 6.02 MeV.

Small impact parameter studies of 2pσ vacancy production in high-Z heavy-ion-atom collisions

K-shell ionisation probabilities were measured for impact parameters between about 10 and 100 fm in collisions between Xe40+ and Sn, Sm, Au and Th. The present data are compared with measurements of ionisation probabilities and total 2p sigma cross sections for other collisions with united-atom atomic numbers up to Zu=184. Also, comparison is made with theories of direct ionisation from the 2p sigma molecular orbital and with a proposed theory involving the two-step transfer of projectile M vacancies into the 2p sigma molecular orbital. The bulk of the high-Z data are in better agreement with the direct ionisation theory.

K-shell ionization in 7.5- and 8.6-MeV/a.m.u. U+U collisions at very small impact parameters

K-vacancy production probabilities in elastic 7.5- and 8.6-MeV/a.m.u. U+U collisions are reported for impact parameters less than 15 fm. In 7.5-MeV/a.m.u. U+U collisions the ionization probability rises above the trend indicated by larger impact parameter measurements, increasing to 1.8 vacancies per collision at the smallest impact parameter. The measured probabilities for 8.6-MeV/a.m.u. collisions increase to a maximum value of slightly less than 2 vacancies per collision at the smallest impact parameters. The data is compared to previous results and existing theory.