低能离子与三原子分子碰撞的俘获解离实验研究

The dissociative ionization of molecules by ion collision is of importance in many areas of science and technology, for example, in studies of astrophyscial plasma, planetary aerospheres and radiation damage of biological tissues. In the low energy ion collision, electron capture dissociation dominates. Previous studies on simple diatomic molecules such as H2 and D2 showed that two-step picture of electron capture and dissociation of molecular ion is no longer valid, and the kinetic energy releases (KER) of fragments are dependent not only on the dissociative energy of molecular ion, but also on the collision process. As for triatomic molecules, there are many channels of electron capture dissociation and the competition between different dissociation channels may occur. The influence of collision process on the dissociation dynamics will become complex. To our best knowledge, there is no report on relevant research. In this project, experiments on triatomic molecules such as N2O and NO2 will be carried out by a collision of low-energy ions offered by the 320-keV platform with highly charged ions in Lanzhou. The fragment ions and the scattered projectile can be measured in coincidence by using reaction microscope. The KER and three-dimensional momentum distributions of fragments, as well as the charge states and momentum of the scattered projectile can be obtained. Various species of ions with different energies and different charge states will be used to explore the influence of collision process on the dissociation dynamics of molecular ions.

离子与分子碰撞的电离解离在天体等离子体、行星大气层及生物组织辐射损伤等研究领域有着重要作用。在低能离子碰撞中，俘获解离过程占据主导。研究表明简单的双原子分子（如：H2, D2）的碰撞俘获和解离的两步机制不再成立，分子解离碎片的动能不仅与解离能有关，还与碰撞过程有关。而对于多原子分子，俘获解离存在多种通道，不同解离通道之间还存在竞争，碰撞过程对解离过程的影响会变得相对复杂，据我们所知，目前还没有相关研究报道。本项目拟用兰州重离子国家实验室320kV高电荷态离子综合研究平台提供的低能离子束与三原子分子（如：N2O, NO2）碰撞，利用反应谱仪对碰撞俘获解离过程产生的分子碎片离子和散射炮弹离子进行运动学完全测量，获得碎片离子的动能和三维动量分布，以及散射炮弹的电荷态和动量，研究碰撞过程对分子离子解离过程的影响，探索不同能量、不同电荷态和不同种类的炮弹离子对分子离子解离通道的调制作用。

离子与分子碰撞的电离解离在天体等离子体、行星大气层及生物组织辐射损伤等研究领域有着重要作用。在低能离子碰撞中，俘获解离过程占据主导。研究表明简单的双原子分子（如：氢分子）的碰撞俘获和解离的两步机制不再成立，分子解离碎片的动能不仅与解离能有关，还与碰撞过程有关。而对于多原子分子，俘获解离存在多种通道，不同解离通道之间还存在竞争，碰撞过程对解离过程的影响会变得相对复杂，据我们所知，目前还没有相关研究报道。我们基于兰州重离子国家实验室的320 kV高电荷态离子综合研究平台，利用56 keV/u的Ne4+ 和Ne8+离子、5.7keV/u和7.2keV/u的 Xe15+离子，与三原子分子N2O、CO2和OCS进行碰撞，通过反应谱仪对碰撞俘获解离过程产生的分子碎片离子和散射炮弹离子进行运动学完全测量，获得了碎片离子的动能和三维动量分布，以及散射炮弹的电荷态和动量；识别了二价和三价分子离子的所有两体解离通道，以及三价分子离子的三体直接库仑爆炸过程和两种顺序解离过程，并通过多电荷态分子离子的库仑爆炸成像，获得了分子的键长和键角；此外，还研究了碰撞过程对分子离子解离过程的影响；分析了不同能量、不同电荷态和不同种类的炮弹离子对分子离子解离通道的作用。本项目获得的实验数据和研究结果将有助于相关理论计算方法的验证，以及较为复杂的多原子分子电离解离研究。