纳秒强激光场中甲醇光电离产生高价离子的研究

利用25ns脉冲Nd YAG 532nm的激光，在1011 W·cm-2的光场强度下，利用飞 行时间质谱对He, N2, Ar载气条件下甲醇的激光电离过程进行了研究.发现当利用氩作为 载气时，除观察到一般多光子电离所产生的离子和碎片离子外，还观察到很强的Cq+(q=2-4)和Oq+(q=2—4)高价离子.这些离子都有很高的平动能，通 过改变载 气种类和压力以及使用不同延迟条件的脉冲电场的实验，可以认为这些高价离子来源于含甲 醇团簇的库仑爆炸过程.这些实验结果为发展库仑爆炸理论研究提供新思路.关键词：甲醇纳秒激光高价离子库仑爆炸

Generation of multi-charged ions in laser-induced ionization of methanol under intense nanosecond laser fields

The photoionization of methanol seeded in He, N2, Ar gases by an inten se 25ns Nd YAG 532nm laser has been studied by time of flight mass spectrome try . At the laser intensity about 1011W·cm-2, strong multi charged io ns Cq+(q=2—4) and Oq+(q=2—4) appeared in the mass spectra apart from the ions coming from multi photon ionization (MPI) process when Ar w as used as a carrier gas. From the simulation, we can find the vel ocity of multi charged ions is distributed in Gaussian shape with a FWHM of 6 4×104 m/s. From the experimental results of changing carrier gases and changi ng the delay time of the pulsed electric field, the conclusion can be drawn that th ose multi charged ions come from the Coulomb explosion of methanol cluster ions .