Field-induced alignment of oxygen and nitrogen by intense femtosecond laser pulses.
Field-induced alignment of oxygen and nitrogen by intense femtosecond laser pulses.
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DOI：
10.1021/jp062391v
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
Juan Huang;Chengyin Wu;N. Xu;Q. Liang;Zhifeng Wu;Hong Yang;Q. Gong
中科院分区：
文献类型：
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作者：
Juan Huang;Chengyin Wu;N. Xu;Q. Liang;Zhifeng Wu;Hong Yang;Q. Gong
在10（13）~ 10（15）W/cm ~ 2的激光强度下，对O_2和N_2的场致取向进行了实验研究。当激光强度低于这些分子的电离阈值时，分子的诱导偶极矩与激光电场之间的相互作用使分子沿激光偏振方向沿着。在激发激光熄灭后，瞬态对准周期性地恢复。因此，宏观合奏的高度对齐的O2和N2分子在无场条件下获得。当激光强度超过这些分子的电离阈值时，发生多电子电离和库仑爆炸。利用两束线偏振的激光脉冲，发现激光脉冲的上升沿使分子在电离前沿激光偏振方向沿着排列，从而导致爆炸碎片的角分布具有很强的各向异性。这些结果表明，在定性比较这些分子与其伴随原子的离子产率时，应考虑到对齐的程度。
Field-induced alignment of O2 and N2 was experimentally studied with laser intensities varying from 10(13) to 10(15) W/cm2. When the laser intensity was below the ionization threshold for these molecules, the interaction between the induced dipole moment of molecules and the laser electric field aligned the molecules along the laser polarization direction. After extinction of the exciting laser, the transient alignment revived periodically. Thus macroscopic ensembles of highly aligned O2 and N2 molecules were obtained under field-free conditions. When the laser intensity exceeded the ionization threshold for these molecules, multielectron ionization and Coulomb explosion occurred. Using two linearly polarized laser pulses with crossed polarization, we demonstrated that the rising edge of the laser pulse aligned the molecules along the laser polarization direction prior to ionization, which resulted in strong anisotropic angular distributions of exploding fragments. These results suggest that the degree of alignment should be taken into account when qualitatively comparing the ion yield of these molecules with their companion atoms.