中文摘要：

利用脉宽为25ns的脉冲Nd：YAG532nm的激光，在10^10-10^44W／cm^2的强度下，用飞行时间质谱对丙酮团簇的激光电离过程进行了研究．观察到了较强的O^1＋（q=2—4）和C^q＋1（q=1-4）高价离子信号，这些高价离子C^4＋,C^3＋.C^2＋,O^4＋,O^3＋,O^2＋的最大概然平动能分别为240eV，70eV，30eV，90eV，80eV，40eV．高价离子的强度和平动能随激光强度的增大而增大．我们提出一个多光子电离引发，逆韧致吸收加热。电子碰撞电离模型来解释高价离子的产生．

英文摘要：

The photoionization of acetone seeded in helium is studied by time-of-flight mass spectrometry using a 25 ns, 532 nm Nd： YAG laser with intensity in the range of 10^10-10^11 W/cm^2 . Multiply charged ions of O^p＋1 （p = 2-4） and C^q＋1 （ q = 2-4） of tens of eV have been observed when the laser beam irradiates the most dense part of the pulsed molecular beam. The intensity and the kinetic energy of the multiply charged ions increase with the increasing of the laser energy. An electron re-scattering and re-colliding ionization model is proposed to explain the appearance of the multiply charged ions under such low laser intensity.