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We perform an experimental study on high-order harmonic generation (HHG) of aligned acetylene molecules induced by a 35-fs 800-nm strong laser field, by using a home-built HHG spectrometer. It is observed that the molecular HHG probability declines with increasing the laser ellipticity, which is in consistence with the deduction from the well-known tunneling-plus-rescattering scenario. By introducing a weak femtosecond laser pulse to nonadiabatically align the molecules, we investigated the molecular orbital effect on the HHG in both linearly and elliptically polarized driving laser fields. The results show that the harmonic intensity is maximum for the molecular axis aligned perpendicularly to the laser electric field. It indicates that both the highest occupied molecular orbitals (HOMO) and HOMO-1 contribute to the strong-field HHG of acetylene molecules. Our study should pave the way for understanding the interaction of molecules with ultrafast strong laser fields.  相似文献   
2.
Bo Yan 《中国物理 B》2021,30(11):114213-114213
We experimentally investigated the high-order harmonic generation (HHG) from aligned O2 and N2 molecules in a linearly polarized laser field, and presented the dependence of the harmonic spectrum on the driving laser intensity and molecular alignment angle. The minimum position of HHG of O2 varies with changing the laser intensity, which is caused by multi-orbital interference. However, the location of the observed minimum structure in N2 harmonic spectrum remained unchanged upon changing the laser intensity. The mechanism of the spectral minimum for N2 case is regarded as a Cooper-like minimum in HHG associated with the molecular electronic structure. This work indicates that harmonic spectroscopy can effectively uncover information about molecular structure and electron dynamics.  相似文献   
3.
李霞  任海振  马日  陈建新  杨宏  龚旗煌 《中国物理》2004,13(9):1564-1568
Femtosecond laser-induced dissociation and Coulomb explosion of polyatomic molecule C_2H_6 were systematically investigated using a time-of-flight mass spectrometer and a chirped pulse amplifier laser. With the laser intensity varying from 2.4×10^{15}W/cm^{2} to 1.2×10^{16}W/cm^2, strong molecular ions C_2H_n^+ (n=0-6) and atomic ions C^{m+} (m=1-3) signals were observed. The double-peak structure of atomic ions indicated the occurrence of Coulomb explosion. Compared with the nearly isotropic distribution of C^{+}, highly charged ions C^{m+} (m=2-3) exhibited a sharply anisotropic angular distribution, which was attributed to the geometric alignment.  相似文献   
4.
We studied the ionization and dissociation of polyatomic molecule methane in an intense femtosecond laserfield with wavelength of 810 nm and intensities ranging from 1.4×10~(14)to 2.6×10~(15) W/cm~2 by massspeetroscopy.Abundant fragment inos were observed in addition to the strong parent ion.The effect offrequency chirp was investigated and it was found that the negatively chirped pulses dramatically enhancedthe dissociation probability,which might be used to control the dissociation pathways.  相似文献   
5.
基于高次谐波产生的极紫外偏振涡旋光   总被引:1,自引:0,他引:1       下载免费PDF全文
突破传统涡旋光场束缚,发展短波极紫外涡旋光场是实现阿秒脉冲偏振控制的有效途径.本研究利用自制的平场光栅光谱仪和超快时间保持的单色仪,以800 nm,35 fs高斯或具有偏振奇点的涡旋光脉冲驱动诱导氩原子产生高次谐波,分别获得相应的高次谐波光谱以及谐波谱单阶光源的分布.实验结果表明,基于高次谐波产生实现近红外波段的涡旋光束特性转移到极紫外波段,优化后的极紫外涡旋可以实现每秒108光子数输出.同时发现极紫外波段的涡旋场和高斯场高次谐波产生具有相似相位匹配机制.基于高次谐波产生的极紫外波段的偏振涡旋光为探究和操控原子分子量子态的含时演化动力学以及形成阿秒矢量光束提供了重要的方法和技术手段.  相似文献   
6.
采用单参考与多参考耦合簇理论结合相关一致高斯基组计算研究了7~7Li_2~((0,±1))分子体系的电子基态的势能曲线,计算考虑了体系所有电子的关联效应与相对论效应,拟合得到了体系的光谱常数,并获得了电子基态的振动-转动能级信息.计算得到的中性与阳离子体系的光谱常数与实验值符合得很好;对于阴离子体系,平衡核间距的计算仍需进一步改进,其他光谱常数符合较好.计算结果表明,中性和阳离子体系基态波函数具有明显的单参考组态特点,而阴离子分子基态应采用多参考组态波函数描述.对于基态的振动-转动能级,与现有实验值符合得很好;尽管各种计算方法对阴离子基态的平衡核间距计算结果仍有差异,但振动能级间隔的结果相互符合得很好.本文的研究可为Li_2分子体系基态,尤其是光谱学信息很少的阴离子体系的电子结构与光谱的精确研究提供了有用的光谱信息.  相似文献   
7.
By using a heated molecular beam in combination with a time-of-flight mass spectrometer, we experimentally study the ionization of vibrational-hot carbon disulfide(CS_2) molecules irradiated by a linearly polarized 800-nm 50-fs strong laser field. The ion yields are measured in a laser intensity range of 7.0 × 10~(12) W/cm~2–1.5 × 10~(14) W/cm~2 at different molecular temperatures of up to 1400 K. Enhanced ionization yield is observed for vibrationally excited CS_2 molecules.The results show that the enhancement decreases as the laser intensity increases, and exhibits non-monotonical dependence on the molecular temperature. According to the calculated potential energy curves of the neutral and ionic electronic states of CS_2, as well as the theoretical models of molecular strong-field ionization available in the literature, we discuss the mechanism of the enhanced ionization of vibrational-hot molecules. It is indicated that the enhanced ionization could be attributed to both the reduced ionization potential with vibrational excitation and the Frank–Condon factors between the neutral and ionic electronic states. Our study paves the way to understanding the effect of nuclear motion on the strongfield ionization of molecules, which would give a further insight into theoretical and experimental investigations on the interaction of polyatomic molecules with strong laser fields.  相似文献   
8.
The kinetic energy release of fragment ions produced by the interaction of femtosecond laser pulse radiation with diatomic and linear triatomic molecules N_2, CO, CO_2 and CS_2 is investigated. In the case of linear polarization, angles at which the kinetic energy release of ions has the maximum value are different from the alignment of molecules though the kinetic energy release of fragment atomic ions depends on the angle between the laser polarization vector and the detection axis of the time-of-flight. For the diatomic molecules, the critical internuclear distance in multielectron dissociative ionization with a circularly polarized light is larger than that with a linearly polarized light. For linear triatomic molecules, our data indicate that a concerted Coulomb explosion process is a universal phenomenon in the interaction of molecules with intense laser fields, even in the circularly polarized regime. During two C-O (or C-S) bonds breaking simultaneously, the C ion obtained larger energy in circular polarization than that in the linear polarization. Different variations of kinetic energy release between the diatomic and the linear triatomic molecules are discussed.  相似文献   
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