中文摘要：

利用伪谱法数值求解碱金属Na原子在中红外激光场中的含时薛定谔方程,在计算中使用了精确的原子模型势函数,通过该模型势能够得到与实验一致的束缚态能级,从而能够研究Na原子处在激发态时发射高次谐波的特点.研究结果表明,在过垒电离区域,当Na原子初态处于4s或5s激发态时发射的高次谐波在阈值之下具有超连续的特点,通过叠加阈值以下到阈值附近的高次谐波,能够得到中心频率从可见光高频波段到中紫外的单个脉冲.通过分析原子的电离概率及谐波的时频特性表明,在过垒电离区域原子发射低阶谐波的过程与隧穿区域发射的过程有所不同.

英文摘要：

The time-dependent Schrodinger equation of alkali metal Na atom in an infrared laser field is solved numerically by using the pseudo-spectral method.In the calculation,an accurate model potential of Na atom is used.The bound state energy levels,which are consistent with experimental data,are obtained with the potential,so that we can study the characteristics of high-order harmonic generation for emission of the exited stated of Na atom.Our results show that the high-order generation spectrum of emission of 4s,and 5s excited states of Na atom is super-continuum in the over-barrier ionization regime.By superposed certain orders harmonics below threshold,a single pulse can be obtained with the central frequency from high frequency of visible light to the ultraviolet band.Through the calculated ionization probability of Na atom and the time-frequency analysis by wavelet transform of the superposed harmonics,it reveals that the emission process of low-order harmonic generation in over-barrier ionization regime is different from in the tunnel ionization regime.