HeH^(2+)分子多通道谐波发射的理论研究

Theoretical exploration of multi-channel harmonic emission of the HeH^(2+) molecule

利用非波恩奥本海默近似模型,理论研究了强激光场下HeH^(2+)分子发射高次谐波的特点.计算结果表明,HeH^(2+)分子的谐波截止能量要大于经典预言值.理论分析表明,延伸的谐波截止能量是由于激发态激光诱导电子跃迁所产生的多通道电子电离-回碰过程所导致的.随后利用双色空间非均匀激光场机制,谐波截止能量进一步延伸,形成了1个由单一量子路径贡献而成的482 eV的超长平台区.该辐射能量相当于单色激光场场强被增强了3倍的结果 .并且高振动激发态会产生强度更高的谐波光谱.最后,通过适当的叠加谐波平台上的谐波,可获得一系列脉宽在30 as的超短X射线光源.

Molecular harmonic generation Born- Oppenheimer time -dependent Sc from HeH2＋ has been theoretically investigated by solving the non - hrt^dinger equation. The results show that the harmonic cutoff of the HeH2＋ is larger than the classical value of the cutoff energy. Theoretical analyses show that the multi - channel i- onization- recombination processes caused by the laser -induced electron transfer are responsible for the har- monic extension. Further, by using the two - color spatially inhomogeneous field scheme, the harmonic cutoff is further enhanced, resulting in a 482 eV supercontinuum with the single quantum path contribution. The extended harmonic cutoff corresponds to a 3.0 dB enhanced field in comparison with the single - color field. Moreover, we found that the intense harmonics can be generated from higher initial vibrational state. Finally, by superposing a properly selected harmonics, a series of attosecond X - ray sources with durations of sub - 30 as can be obtained.