低能离子注入植物种子深度的研究

Penetrating depth for ion with low energy implanted in plant seeds

为了研究种子内部空洞大小对注入离子穿行深度的影响,基于注入离子穿行过程的随机性及与植物种子内靶原子碰撞的微观过程,建立注入离子在植物种子内穿行过程的非平衡统计理论模型,求解与广义朗之万方程等价的Fokker-Planck方程,得到穿行深度概率密度分布函数。在此基础上,计算出注入离子与不同靶原子碰撞所走的平均穿行深度并进行比较,分析种子内部涨落的存在、引起的注入离子平均穿行深度的变化及植物种子内部空洞占不同体积比时对注入离子穿行深度概率密度的影响等。以入射能量为30 ke V的N^+注入到植物种子糙米中为例,计算了平均穿行深度,比较了空洞大小对N^+穿行深度的影响。结果表明:糙米种子内部空洞体积越大,N^+的穿行深度越大。

[Background] Low-energy ion implantation is a new biological mutation source possessing the characteristics of high mutation rate and light damage, which extends the ion beam bio-engineering. [Purpose] This paper aims to study the depth of ion implantation in seeds by making better use of ion beam for bio-engineering. [Methods] Considering the size of the void volume, a non-equilibrium statistical theory model was proposed for easy analysis of the penetrating process. The dynamic penetrating process was studied by combining the range theory model of the collision and the non-equilibrium statistical theory model of low-energy ion implanting into plant seeds. Probability density function of penetrating depth was deduced by solving the Fokker-Planck function which is equivalent to the general Langevin equation. [Results] The average penetrating depth of nitrogen ions at projectile energy of 30 keV in brown rice seeds was calculated, and the influence of the cavity inside the seeds on the penetrating depth of ions was analyzed by comparison. [Conclusion] The existence of the cavity inside the plant seeds is an important reason to increase the penetrating depth of implanted ions, the bigger of the cavity, the deeper of the penetration.