电离效率对激光电离团簇的高价离子产物的影响  

The influence of ionization efficiency on the multiply charged ions produced by laser-clusters interaction

作　　者：曲丕丞[1,2] 王卫国[2] 赵无垛[2,3] 张桂秋[1] 李海洋[2] 

机构地区：[1]山东师范大学化学化工与材料科学学院,济南250014 [2]中国科学院大连化学物理研究所,分子反应动力学国家重点实验室,大连116023 [3]中国科学院研究生院,北京100049

出　　处：《物理学报》2012年第18期101-106,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11004190,21077101);国家重大科学仪器设备开发专项(批准号:2011YQ05006903,2011YQ05006904);辽宁省自然科学基金(批准号:201102220)资助的课题~~

摘　　要：纳秒激光与团簇相互作用产生高价离子逐渐成为分子物理界的热点之一,为了深入研究团簇电离的本质,本文以分子结构相似、元素组成相同的苯、环己烯和环己烷的分子团簇为对象,利用飞行时间质谱研究了其与5 ns的532 nm激光相互作用时电离产物的价态和强度分布.结果表明:这三种化合物多光子电离效率苯>环己烯>环己烷,但其高价离子的价态和比值苯是最低的,环己烷的碳离子最高价态为4价,C^(3+)和C^(2+)的比值为1.1;环己烯电离产物C^(3+)和C^(2+)的比值降低为0.6;苯团簇的最高价态只有3价,C^(3+)和C^(2+)的比值约为0.4.引起这种现象的原因可以归结于高的多光子电离效率会导致团簇多位点的电离,引起团簇在电子加热到发生碰撞电离之前发生解离,减小了团簇的尺寸,进而减少了离子发生碰撞电离产生高价离子的反应时间,最终阻碍了高价态离子的产生.The productions of multiply charged ions in the interactions of intense nanosecond laser pulse with clusters have aroused broad interests in molecular physics. Benzene, cyclohexene and cyclohexane clusters are chosen to study the effect of multiphoton ionization （MPI） efficiency on the relative intensity of multiply charged ions, as they possess similar molecular structures and the same element constitutions. They are ionized with a 5 ns Nd-YAG nanosecond laser. The carbon charge state produced by cyclohexene and cyclo- hexane is about 4; while by benzene is only about 3. The ratios of Ca＋/C2~ for cyc/ohexane, cyclohexene and benzene are 1.1, 0.6 and 0.4, respectively. The relative MPI efficiencies of three molecules are measured to be in the magnitude sequence of benzene 〉 cyclohexene 〉 cyclohenane by diffusion beam. Higher MPI efficiency of molecules can cause more than one molecules to be ionized at the edge of laser pulse, the Coulomb repelling force between adjacent ions leads clusters to early split into small size ones, which will prevent the production of the highly charged ions.

关 键 词：团簇 高价离子 多光子电离 苯 

分 类 号：O561[理学—原子与分子物理]