对称和不对称分子谐波辐射与其结构的内在关系  

Internal Relationship between Symmetrical and Asymmetric Molecular Harmonic Radiation and Its Structure

作　　者：于术娟 刘竹琴[1] 曹冬梅[1] 刘艳峰[1] 李雁鹏 YU Shujuan;LIU Zhuqin;CAO Dongmei;LIU Yanfeng;LI Yanpeng(College of Physics and Electronic Information,Yan'an University,Yan'an,Shaanxi 716000,China)

机构地区：[1]延安大学物理与电子信息学院,陕西延安716000

出　　处：《光子学报》2022年第3期347-356,共10页Acta Photonica Sinica

基　　金：国家自然科学基金(No.11904310);延安市专项基金(No.2019-03)。

摘　　要：通过数值和解析相结合的方法研究了对称和不对称分子谐波辐射与其结构的内在关系。首先应用虚实演化法得到了对称分子H^(+)_(2)和不对称分子HeH^(2+)的基态波函数的数值表达式,从基态波函数出发,计算了束缚-连续态跃迁偶极矩,并与纯解析方法得到的跃迁偶极矩进行了比较。结果表明:对于对称分子H^(+)_(2),用虚实演化方法计算得到的基态波函数显著改善了奇次偶极矩和奇次谐波谱的一致性;对于不对称分子HeH^(2+),得到的基态波函数显著改善了奇偶偶极矩最小值和奇偶谐波极化最大值之间的一致性;结果验证了高次谐波谱与跃迁偶极矩之间的一一对应关系。通过跃迁偶极矩可重构分子轨道,从而深入了解对称分子高次谐波与对称分子轨道之间的相互关系及不对称分子奇偶高次谐波与不对称分子轨道之间的相互关系。For symmetric molecules,only odd harmonics are emitted.In particular,the high-order harmonic spectrum shows a significant minimum which corresponds to the minimum in the dipole moment of the bound-continuous state transition.For asymmetric molecules,both odd and even harmonics are emitted.However,in many cases,the striking minimum disappears in the odd or even harmonic spectrum.Fortunately,when the minimum cannot be read from the harmonic spectra directly,it can be probed through the polarization measurement of the odd-even high-order harmonic generation.Specifically,the position of the minimum in the odd or even dipole corresponds to the harmonic order for the maximal ellipticity of the odd or even harmonics.However,for symmetric molecules H^(+)_(2),the minimum in the transition dipole is not completely consistent with the minimum of the harmonic spectra.For asymmetric molecules HeH^(2+),the prediction of the dipole minimum by the polarization measurement does not always agree well with the theoretical evaluation.In some cases,a remarkable difference is also observed.This remarkable difference may arise from other mechanisms beyond the description of the simple model,or the inaccurate calculation of dipole moment may be caused only by some rough approximate in relevant theoretical treatments.In this paper,this question is explored by improving the calculation of the dipole moment.The intrinsic relationship between harmonic radiation and the structure of symmetric and asymmetric molecules is studied by a combination of numerical and analytical methods.First,the numerical expressions of the ground state wave functions of symmetric and asymmetric molecules are obtained using the virtual time evolution method.Starting from the accurate ground state wave functions of symmetric and asymmetric molecules,the bound-continuous state transition dipole moments are calculated.The term proportional to the nuclear separation is further subtracted from the transition dipole moment.For symmetric molecules H^(+)_(2),the calculate

关 键 词：高次谐波 跃迁矩阵元 数值法 解析法 对称分子 不对称分子 

分 类 号：O562[理学—原子与分子物理]