Study Of Double K-shell Ionization Process In Relativistic Ion-atom Collisions

The K-shell hollow atoms are of great scientific values both for fundamental physics and also for various application fields,such as X-ray laser,high energy density physics,molecular imagine,and so on.In view of the difficulties in producing isolated heavy hollow atoms with a high yield,the present thesis proposes a method to produce such atoms in gaseous targets bombarded by relativistic heavy-ions at the storage rings with an internal target,which satisfies the requirements of the isolation condition.The production mechanism,vacancy configurations and decay properties of K-shell hollow Kr and Xe atoms created with the collisions of the corresponding gaseous targets by 52-197 MeV/u Xe⁵⁴⁺ at HIRFL-CSRe were studied.The cross section ratios of double-to-single K-shell ionization were determined from the measurements of the target K X hypersatellites and satellites.Combined with the calculation of the fluorescence yields of the multi-vacancy state atoms,the relative intensities of the K? hypersatellites and satellites showed that the cross-section ratios of double-to single-K-shell ionization,R₂1,for krypton are 14.9–25.2%,and those for xenon are 17.3-27.9%.The ionization probabilities of double electron processes at the collisions were calculated by solving the two-center time-dependent Dirac equations within independent particle approximation.The experimental results demonstrated a linear dependence of R₂1 on ? = Zp/vp as well as the right slope at the range of ?<1 which were well reproduced by the theoretical calculations with the relativistic coupled-channel approach?RCC?.The average numbers of the spectator L-vacancies during the x-ray emission were also deduced from the energy shifts of the K? hypersatellites and satellites.Combined with the simulation of multi-step vacancy rearrangement processes,the values of the average numbers of spectator L-vacancies accompanying double K-shell ionization were deduced.In particular,we find that with increasing the projectile energy the mean L-shell vacancies values accompanying with the K-shell ionization decrease.It was also shown that more spectator L-vacancies were created accompanying double K-shell ionization than single K-shell ionization.The measured intensity ratios of Xe K?1 and K?2 hypersatellites show that they increase with the increase of mean number of the spectator L-vacancies,and agree with the theoretical results of radiative deexcitation from open shell hollow atoms with intermediate coupling states.The present work shows that a heavy ion storage ring,equipped with an internal gas-jet target,is an efficient setup to produce free and heavy K-shell hollow atoms.By utilizing different kinds of projectile ions,K-shell hollow atoms with different additional L-vacancies could be investigated systematically.With the new generation of storage rings which will be available in the near future,the ion beam will be more intensive by three orders of magnitude than present ones,thus factories to produce a large amount of free and heavy K-shell hollow atoms can be expected.