Theoretical study of electronic transitions in relativistic heavyion collisions
Project/Area Number  02640288 
Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
物理学一般

Research Institution  University of Tsukuba 
Principal Investigator 
TOSHIMA Nobuyuki Univ. Tsukuba Appl.Phys. Assoc.Prof, 物理工学系, 助教授 (10134488)

Project Period (FY) 
1990 – 1992

Project Status 
Completed(Fiscal Year 1992)

Budget Amount *help 
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1992 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1991 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1990 : ¥1,400,000 (Direct Cost : ¥1,400,000)

Keywords  relativistic / coupledchannel / boundary condition / Thomas peak / secondBorn / ポジトロン散乱 / 2次ホルン / イオン衝突 / トマス過程 / 相対論的衝突 / クロン境界条件 
Research Abstract 
It is known from the study of Toshima and others that special account of the longrange of Coulomb interactions is not needed in the nonrelativistic coupledchannel approach. We have shown that this is not the case for relativistic ionatom collisions and distortedwave formalism must be used even for coupledchannel method in order to make the transition matrix welldefined. It was demonstrated by numerical calculations based on the distortedwave method that the cross sections for the system U^<92+>+U^<91+> change more than a factor of two by this effect. The symmetric eikonal approximation, which is a symmetrized version of the traditional eikonal theory, has been used widely because of the simplicity of the formula. We pointed out from both analytic and numerical calculations that the symmetric eikonal formula does not satisfy the correct coulomb boundary conditions and it gives unphysically large spinflip cross sections owing to this defect. It is widely known that the secondor
… More
der contribution becomes dominant at high energies for electron capture processes. As a result the differential cross section shows a sharp peak at a critical angle and this peak is called the Thomas peak. Although the dominance of the secondorder term implies the inadequacy of the perturbation theory itself, all of the theoretical studies for the Thomas mechanism were based on the perturbation theory. We developed a new coupledchannel code based on Gausstype orbital expansion and succeeded in producing the Thomas peak by nonperturbative method for the first time. By this study it was demonstrated that the Thomas peak is shifted to smaller scattering angle side and a thirdorder process is contributing significantly owing to a multiscattering effect. Besides we carried out the classical trajectory Monte Carlo calculation for the Thomas mechanism and showed that the Thomas peak is unexpectedly missing in the pure classical treatment. Exact calculation of the secondBorn terms was also realized for the first time for rearrangement collisions into exited states and destructive and constructive interference effects were reported. Less

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Research Products
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