High harmonic spectroscopy of electron localization in the hydrogen molecular ion
High harmonic spectroscopy of electron localization in the hydrogen molecular ion
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DOI：
10.1088/0953-4075/47/20/204015
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发表时间：
2014-10-28
影响因子：
1.6
通讯作者：
Martin, Fernando
中科院分区：
文献类型：
--
作者：
Morales, Felipe;Riviere, Paula;Martin, Fernando
激光脉冲与中心对称介质（如各向同性原子气体）的相互作用会产生谐波发射，该发射只包含入射场的奇次谐波。这个结果是介质的中心对称性和振荡电场的时间对称性的结果，E(t + pi/omega(l))= -E(t)，其中omega(l)是激光频率。在取向异核分子的情况下，空间对称性不再成立，奇偶谐波都是允许的。本文通过求解H-2（+）、D-2（+）和T-2（+）的时变薛定谔方程，证明了在同核分子中，对于足够长的红外（IR）激光脉冲，偶阶谐波产生也是可能的。均匀谐波的出现是电子-核耦合动力学的特征，反映了强激光场引发的场致电子局域化，破坏了系统的空间对称性。因此，对不同持续时间脉冲产生的均匀谐波的分析可能为更复杂的无取向分子系综中相关的电子-核动力学和电荷迁移提供信息。
Interaction of a laser pulse with a centrally symmetric medium, such as an isotropic gas of atoms, leads to the generation of harmonic emission which contains exclusively odd harmonics of the incident field. This result is the consequence of both the central symmetry of the medium and the temporal symmetry of the oscillating electric field, E(t + pi/omega(l))= -E(t), where omega(l) is the laser frequency. In the case of oriented heteronuclear molecules, the spatial symmetry no longer holds and both odd and even harmonics become allowed. Here we show, by solving the time-dependent Schrodinger equation for H-2(+), D-2(+), and T-2(+), that even-order harmonic generation is also possible for sufficiently long infrared (IR) laser pulses in homonuclear molecules. The appearance of even harmonics is a signature of the coupled electron-nuclear dynamics and reflects field-induced electron localization initiated by the strong laser field, which breaks the spatial symmetry in the system. The analysis of even harmonics generated by pulses of different durations might therefore provide information on correlated electron-nuclear dynamics and charge migration in more complex un-oriented molecular ensembles.