Theoretical study of antiparticle collisions and exotic-atom formation

(1)采用大尺度超球面紧密耦合方法研究了原子对正电子的散射。对于氦原子靶，我们采用了一种基于准单电子原子近似的模型势，该模型势非常准确地再现了电离势。在原子分离极限下，所有与n=1-4的氦原子态和n=1-5的正电子态相关的绝热通道函数都完全耦合。所得的地层截面与实测值吻合较好，是目前理论值中最接近的。在电子被正电子散射的情况下，明确地研究了包括自旋-自旋相互作用在内的超精细结构跃迁。我们还研究了正电子负离子的feshbach型共振，并系统地制表了宽能区内的能量位移和宽度。(2)采用基于伪态展开的大尺度冲击参数紧密耦合方法，研究了反质子与更多氦原子和氦离子碰撞时反质子氦的形成。精确计算了n=38附近的高激发态，为波函数角部的分解提供了一种新方法。俄歇衰变的能量特征值和寿命与测量结果非常吻合。用离散化的伪连续态来表示电离通道，分析了第一阶段的反质子俘获。为了比较，还系统地计算了质子撞击散射。(3)结合介子催化聚变研究，研究了氢同位素间的介子转移。发现激发态的转移截面比基态的大几百倍。这是由简并激发态的大偶极矩引起的远距离相互作用引起的。发现了菲什巴赫型共振，其截面受到很大影响。少

(1) Positron scattering by atoms was studied by means of a large-scale hyperspherical close-coupling method. For the helium atom target we employ a mdel potential which reproduces the ionizaiton potential very accurately on the basis of the quasi single-electron atom approximaiton. All the adiabatic channel functions are coupled fully that are associated with the helium atomic states with n=1-4 and positronium states with n=1-5 in the separated -atom limit. The obtained formation cross sections agree well with the measured values and the present results are the bast among available theoretical values so far. In the case of electron scattering by positronium, hyperfine-structure transitions are studied including the spin-spin interactions explicitly. We also studied Feshbach-type resonances of the positronim negative-ion and tabulated systematically the energy shifts and widths in a wide energy region.(2) Formation of antiprotonic helium was studied in the collisions of antiproton with … More helium atoms and helium ions using a large-scale impact-parameter close-coupling method based on the pseudo state expansion. Highly excited states around n=38 are calculated accurately developing a new method for the decomposition of angular parts of wave functions. The energy eigenvalues and the life times of Auger decays agree excellently with measurements. The antiproton trapping in the first stage is analyzed representing ionization channles in terms of discretized pseudo continuum states. Proton-impact scattering was also calculated ststematically for comparison.(3) Muon transfer between hydrogen isotopes was studied in connection with the muon-catalyzed fusion reseach. The transfer cross sections from excited states are found to be larger than that from the ground state by several hundreds times. This is caused by the long-range interaction induced by the large dipole moment of the degenerate excited states. Feshbach-type resonaces are found and the cross sections are influenced considerably. Less