结合数值参数优化有效势模型与拟谱-分裂算符方法,研究了强激光场下碱金属原子气的 高次谐波产生过程。基于参数优化有效势特点对演化矩阵进行了处理,保证了演化过程中含时波函数 与闭壳层轨道的正交性。选取波长为3038 nm、强度约1013 W/cm2的中红外激光场作为驱动场,计算了锂、 钠、钾原子的高次谐波谱。研究了长激光脉宽下里德伯态钠原子束缚态跃迁峰对谐波产生的贡献,结果表 明里德伯态与基态的共振会使低阶谐波的强度增加一个量级,验证了该方法描述含时演化过程中电子重俘获过程的可靠性。

By combining the numerical-parameterized optimized effective potential (NPOEP) model and pseudospectral method, the high-harmonics generation(HHG) process of alkaline metal atoms in intense laser field is investigated. The evolution matrix is modified based on the features of NPOEP model. The orthogonality of time-dependent wave function with closed-shell orbit in evolution process is ensured. The mid-infrared laser field with a wavelength of 3038 nm and intensity of about 1013 W/cm2 is chosen as the driving field, and the high-order-harmonic spectra of lithium, sodium and potassium atoms are calculated. Contributions of bound state transition harmonics of Rydberg state sodium atom on harmonic generation are investigated. Results show that the resonance of Rydberg and ground state can make the low-order harmonic intensity increase by one order of magnitude. It is verified that the method is reliable in describing the process of electron recapture during time evolution.