【摘要】 用波长为800nm,脉宽为160fs,强度范围为7.6×1013～1.4×1014W·cm-2的强激光使甲烷分子解离,并用质谱仪检测产生的离子.母体离子在较低的激光强度(7.6×1013W·cm-2)下出现;当激光强度增加到8.0×1013W·cm-2时,CH3+开始出现;CH2+、CH+和C+离子出现的阈值分别为1.0×1014W·cm-2,1.4×1014W·cm-2和1.4×1014W·cm-2.这些现象表明甲烷的解离是一个顺序过程.质谱图中没有多电荷离子,因此排除了发生库仑爆炸的可能.以线偏振激光作用于甲烷,只有H+离子有各向异性的角度分布,暗示分子中的化学键是被激光外场拉断的,且初级产物离子H+是沿着激光电场的方向飞出.提出的准双原子分子模型较好地解释了实验结果.更多还原

【Abstract】 Methane molecules were irradiated by a laser beam in the intensity range of 7.6 ×1013～1.4×1014 W·cm-2 (800 nm, 160 fs). A time of flight mass spectrometer was coupled to the laser system. The parent ionscan be seen at low laser intensity of 7.6×1013 W·cm-2. When the laser intensity increases to 8 .0×1013 W·cm-2, ions appear. The appearance of the , CH+, C+ ions are at the laser intensities of 1.0×1014 W·cm-2,1.4×1014 W·cm-2 and 1.4×1014 W·cm-2, respectively. The facts show that dissociation of methane is a step wise process. Coulomb explosion does not happen during the dissociation because no multi electron ions are found in the mass spectra. Only H+ ion yield has anisotropic angular distribution when methane isirradiated by a linearly polarized laser. This fact implies that the chemical bonds in the molecule are pulled off by the laser field and that the H+ ion flies along the direction of the laser electronic field. The quasi diatomic molecule model we proposed can explain the experimental results satisfactorily.更多还原