飞秒强激光场中大尺寸氩团簇爆炸机理的实验研究  

Experimental study on explosion mechanism of large agron clusters in intense laser pulses

作　　者：李邵辉[1,2] 王成[1] 刘建胜[1] 王向欣[1] 李儒新[1] 倪国权[1] 徐至展[1] 

机构地区：[1]中国科学院上海光学与精密机械研究所强光实验室 [2]汕头大学物理系,汕头515063

出　　处：《物理学报》2005年第2期636-641,共6页Acta Physica Sinica

基　　金：国家重点基础研究专项基金 (批准号 :G19990 75 2 0 0 );国家自然科学基金 (批准号 :2 9890 2 10 )资助的课题~~

摘　　要：利用飞行时间谱 ,研究了在飞秒强激光场 (6 0fs,2× 10 1 6 W cm2 )作用下 ,大尺寸氩原子团簇Arn(n— =3× 10 3— 3× 10 6 原子 每团簇 )的电离爆炸过程 ,测量了团簇爆炸所产生的氩离子的平均能量与团簇尺寸 (气体背压 )的关系 .实验发现 ,随着气体背压的升高 (团簇尺寸增大 ) ,氩离子的平均能量也相应升高 .通过分析两个不同几何尺寸锥形超声喷嘴所产生团簇爆炸后的离子能量 ,结合Hagena团簇尺寸规律 ,发现在激光参数保持不变的情况下 ,离子的平均能量由团簇尺寸唯一确定 .分析表明 ,团簇尺寸在 3× 10 5原子 每团簇以下时 ,团簇膨胀的主要机理是库仑爆炸 .随着团簇尺寸的进一步增大 ,团簇膨胀机理将由库仑爆炸向流体动力学膨胀过渡 ,在 3× 10 5<n— <3× 10 6 范围 ,氩团簇爆炸为两者共同作用的结果 .By using time-of-flight spectroscopy, the ionization and explosion of large argon clusters ( (n) over bar = 3 x 10(3) - 3 x 10(6)) in the intense femtosecond pulsed laser field (60 fs,2 x 10(16) W/cm(2)) has been studied, and the dependence of average energy of ions emitted from argon clusters on the gas backing pressure has been measured. By comparing the average ion energies obtained with two different supersonic conical nozzles and considering the Hagena's scaling law of clusters, we have found that the average ion energy is determined by the cluster size when the laser parameters are kept unchanged. The experimental results indicated that when the cluster size is less than 3 x 10(5) atoms per cluster, the Coulomb repulsion force is the dominating factor in the expansion mechanism. Beyond this size, for 3 x 10(5) < (n) over barn < 3 x 10(6), the expansion is the result of the combined effect of both the Coulomb repulsion force and the hydrodynamic force, and the latter will play the dominating role for increasing cluster size.

关 键 词：团簇 强激光场 平均能量 库仑爆炸 飞行时间谱 氩原子 飞秒 激光参数 大尺寸 氩离子 

分 类 号：O4-33[理学—物理]