Collision between two ortho-positronium (Ps) atoms: A four-body Coulomb problem

Pramana

RAY HASI1 2 3¹ 

[1] Study Centre, S-1/407/6, B.P. Township, Kolkata 700 094, India$$

关键词: Positronium;    elastic collision;    exact exchange;    CM frame;    scattering length;    quenching cross-section;    non-adiabatic effects.;   

DOI  :  

学科分类：物理（综合）

来源: Indian Academy of Sciences

【 摘 要 】

The elastic collision between two ortho-positronium (e.g. $S = 1$) atoms is studied using an {it ab-initio} static exchange model (SEM) in the centre of mass (CM) frame by considering the system as a four-body Coulomb problem where all the Coulomb interaction terms in the direct and exchange channels are treated exactly. A coupled channel methodology in momentum space is used to solve Lippman–Schwinger equation following the integral approach. A new SEM code is developed in which the Born–Oppenheimer (BO) scattering amplitude acts as input to derive the SEM amplitude adapting the partial wave analysis. The $s$-, $p$- and $d$-wave elastic phase shifts and the corresponding partial cross-sections for the spin alignment $S = 0$, i.e., singlet (+) and $S = 2$, i.e., triplet (−) states are studied. An augmented Born approximation is used to includethe contribution of higher partial waves more accurately to determine the total/integrated elastic cross-section $(sigma)$, the quenching cross-section (σq) and ortho-to-para conversion ratio $(sigma/sigma q)$. The effective range theory is used to determine the scattering lengths and effective ranges in the s-wave elastic scattering. The theory includes the non-adiabatic short-range effects due to exchange.

【 授权许可】

Unknown