Theory of Electronic and Nuclear Wavepacket Dynamic (Application to the structure deformation and electron transfer of molucular in laser field)

为了理解强场中的超快电子动力学，我们开发了一种有效的网格点法，即对偶变换法，用于求解分子电子自由度随时间变化的薛定谔方程。我们已经将这种方法应用于小分子体系，如H_2。振动自由度也被纳入H^+_2的计算中，而不需要采用玻恩-奥本海默近似。在长波长情况下，对于H_2，局域离子（键）态H^+H^-和H^-H^+根据光循环交替出现，通过光循环隧道电离进行。H_2经过单电子电离后，在H_2的平衡核间距离附近生成H^+_2。H^+_2的键距被外加电场拉长。借助从头算分子轨道计算，我们还证明了CO_2阳离子对称双键拉伸等强场动力学的分子结构变形特征。波包方法使强激光场中电子-核相关和双电子动力学的可视化成为可能。电子运动可以通过调节强度、频率和脉冲长度来控制。作为一个例子，我们研究了H_2在短波长（~ 100 nm）下的电子动力学。与长波长的情况相反，电子对是在质子附近产生的，在质子附近偶极相互作用能变得更高。非定常态H^+H^-和H^-H^+交替出现，即使在入射脉冲完全衰减后也有分子固有的周期。原子核间的超快电子跳跃可以用第二个脉冲来控制。使用这种双脉冲方案，我们能够增强或抑制电离。

To understand the ultrafast electronic dynamics in intense fields, we have been developing an efficient grid point method, the dual transformation method, for solving the time-dependent Schrodinger equation for the electronic degrees of freedom of a molecule. We have applied this method to small molecular systems such as H_2. The vibrational degree of freedom is also incorporated in the calculation of H^+_2 without resorting to the Born-Oppenheimer approximation.In a long wavelength case, for H_2, the localized ionic (bond) states H^+H^- and H^-H^+ appear alternately according to the optical cycle, through which tunnel ionization proceeds. After one-electron ionization from H_2, H^+_2 is prepared around the equilibrium internuclear distance of H_2. The bond distance of H^+_2 is then stretched by the applied field. With the help of ab initio molecular orbital calculations, we also demonstrate molecular structure deformations characteristic of intense-field dynamics such as symmetric two-bond stretching of CO_2 cations. The wave packet approach enables visualization of electron-nucleus correlation and two-electron dynamics in intense laser fields.Electronic motion can be controlled by adjusting the intensity, frequency, and pulse length. As an example, we have examined the electronic dynamics of H_2 in a short wavelength case (〜100 nm). Contrary to the long wavelength case, the electron pair is created near the proton at which the dipole interaction energy becomes higher. The nonstationary states H^+H^- and H^-H^+ appear alternately with a period inherent to the molecule even after the incident pulse has fully decayed. Ultrafast electron hopping between the nuclei can be controlled by a second pulse. Using this two-pulse scheme, we are able to enhance or suppress the ionization.