Harmonic and attosecond pulse enhancement in the presence of noise

<正>In this paper,we theoretically investigate the effect of noise on the photoionization,the generation of the high-order harmonic and the attosecond pulse irradiated from a model He~+ ion.It shows that by properly adding noise fields,such as Gaussian white noise,random light or colored noise,both the ionization probabilities(IPs) and the harmonic yields can be enhanced by several orders of magnitude.Further,by tuning the noise intensity,a stochastic resonance-like curve is observed,showing the existence of an optimal noise in the ionization enhancement process.Finally,by superposing a properly selected harmonic,an intense attosecond pulse with a duration of 67 as is directly generated.     

O + NH反应在3A’’和1A’’势能面上的量子含时波包动力学研究

对于O + NH反应,在3A’’和1A’’ 势能面（Guadagnini R, Schatz G C, Walch S P. Global potential energy surface for the lowest 1A’, 3A’’, and 1A’’ states of HNO [J]. J. Chem. Phys., 1995,10:774）上,我们运用coupled state or centrifugal sudden (CS)近似和close coupling or Coriolis coupled (CC)方法进行了量子动力学计算。通过比较两种方法得到的总的反应几率,我们发现对于两个势能面上的标题反应,CS近似是失效的。我们还讨论了用CS和CC方法得到的速率常数,并进行了结果比较。     

Mechanism of Excited State Double Proton Transfer in 2-Amino-3-Methoxypyridine and Acetic Acid Complex

The excited-state double-proton transfer(ESDPT) mechanism of 2-amino-3-methoxypyridine and acetic acid complex is studied by the density functional theory(DFT) and time-dependent DFT with CAM-B3LYP functional.The complex is connected through two different types of inter-molecular hydrogen bonds. After photo-excitation,both hydrogen bonds get strengthened, which can facilitate the ESDPT reaction. The scanned potential energy curve along the proton transfer coordinate indicates that the ESDPT reaction proceeds in a stepwise pattern.     

O+NH反应在3A″和1A″势能面上的量子含时波包动力学研究

对于O+NH反应,在3A″和1A″势能面(Guadagnini R,Schatz G C,Walch S P.Global potential energy surface for the lowest 1A′,3A″,and 1A″states of HNO [J].J.Chem.Phys.,1995,10:774)上,我们运用coupled state or centrifugal sudden (CS)近似和close coupling or Coriolis coupled (CC)方法进行了量子动力学计算.通过比较两种方法得到的总的反应几率,我们发现对于两个势能面上的标题反应,CS近似是失效的.我们还讨论了用CS和CC方法得到的速率常数,并进行了结果比较.     

Low-energy structure in the ionization of argon: Comparison of experiment with theory

The above-threshold ionization of argon in an intense 70-fs,400-nm linearly polarized laser pulse has been investigated by the velocity map imaging techniques,combined with an attosecond-resolution quantum wave packet dynamics method.There is a quantitative agreement in all dominant features between the experiment and the theory.Moreover,a peak-splitting phenomenon in the first energy peak has been observed at high pulse intensity.Further,through the theoretical analysis,an ac Stark splitting with evident resonant and nonresonant ionization pathways has been found to be the physical reason for the experimental observations.     

"医学影像物理基础"教学内容现代化的一点尝试

介绍了为推进医学影像物理基础课教学内容的现代化，在内容重新组合，新知识的引入，联系实际与教学内容的深化四个方面所进行的尝试。     

0.5 eV时H++D2(v=0,j=0) 反应的微分、积分截面

基于ab initio势能面(KBNN PES)[1],用耦合通道超球坐标理论研究了碰撞能等于0.5 eV时H D2(v=0,j=0)的积分,微分截面.对于反应性碰撞,计算的积分截面表明由于深势阱的存在使得这一绝热反应产物的分布表现出一种近似的统计行为.计算的微分截面反映该体系存在着长寿命的中间络合物;对于非反应性碰撞(传能过程),平动—平动传能过程更有效,且其积分截面随着转动量子数的增大而显著减少.通过反应性碰撞和非反应性碰撞积分截面的比较,发现在低能碰撞情况,非反应性碰撞更容易进行.     

The stereodynamic properties of the F+HO(v,j) → HF+O reaction on~1 A' and ~3A' potential energy surfaces by quasi-classical trajectory calculations:Initial excitation effect(v=1-3, j=0 and v= 0, j=1-3)

The stereodynamic properties of the F ＋ HO （v, j） reaction are explored by quasi-classical trajectory （QCT） calculations performed on the 1At and 3At potential energy surfaces （PESs）. Based on the polarization-dependent differential cross sections （PDDCSs） and the angular distributions of the product angular momentum with the reactant at different values of initial v or j, the results show that the product scattering and product polarization have strong links with initial vibrationalrotational numbers of v and j. The significant manifestation of the normal DCSs is that the forward scattering gradually becomes predominant with the initial vibrational excitation increasing, and the scattering angle of the HF product taking place on the 3At potential energy surface is found to be more sensitive to the initial value of v. The product orientation and alignment are strongly dependent on the initial rovibrational excitation effect. With enhancement in the initial rovibrational excitation effect, there is an overall decrease in the product orientation as well as in the product alignment either perpendicular to the reagent relative velocity vector k or along the direction of the y axis, for which the initial rotational excitation effect is much more noticeable than the vibrational excitation effect. Moreover, the initial rovibrational excitation effect on the product polarization is more pronounced for the 3At potential energy surface than for the 1At potential energy surface.     

用精确的量子力学方法研究N + OD反应的动力学性质

采用close coupling (CC)方法,在3A’’势能面上[Guadagnini R, Schatz G C, Walch S P. Global potential energy surface for the lowest 1A’, 3A’’, and 1A’’ states of HNO [J]. J. Chem. Phys., 1995,10:774],我们利用量子含时波包方法对N + OH的同位素反应—N + OD进行了研究。在0.0-0.8 eV的平动能范围内,选态的反应几率受共振结构支配。利用 -shifting方法计算,我们得到了基态的速率常数,并对分子间的同位素效应进行了研究。     

The stereodynamic properties of the F + HO (v,j)→HF + O reaction on the 1A' and 3A' potential energy surfaces by quasi-classical trajectory: Initial excitation effect (v =1-3, j = 0 and v = 0, j =1-3)

The stereodynamic properties of the F + HO (v, j) reaction are explored by quasi-classical trajectory (QCT) calculations performed on the ¹A' and ³A' potential energy surfaces (PESs). Based on the polarization-dependent differential cross sections (PDDCSs) and the angular distributions of the product angular momentum with the reactant at different values of initial v or j, the results show that the product scattering and product polarization have strong links with initial vibrational-rotational numbers of v and j. The significant manifestation of the normal DCSs is that the forward scattering gradually becomes predominant with the initial vibrational excitation increasing, and the scattering angle of the HF product taking place on the ³A' potential energy surface is found to be more sensitive to the initial value of v. The product orientation and alignment are strongly dependent on the initial rovibrational excitation effect. With enhancement in the initial rovibrational excitation effect, there is an overall decrease in the product orientation as well as in the product alignment either perpendicular to the reagent relative velocity vector k or along the direction of the y axis, for which the initial rotational excitation effect is much more noticeable than the vibrational excitation effect. Moreover, the initial rovibrational excitation effect on the product polarization is more pronounced for the ³A' potential energy surface than for the ¹A' potential energy surface.