辅助光对NaCl(OH-)和KCl(Na+,OH-)晶体中的类F2+型色心激光输出的影响

文中报进了有关辅助光对NaCl(OH^-):(F₂⁺)_H及KCl(Na⁺,OH^-):(F₂⁺)_AH色心激光输出功率影响的主要研究结果。初步探讨了辅助光作用的物理机制。     

X形色心激光谐振腔参数的确定及类F2+型色心激光运转

文中,针对X形谐振腔的特点及结合纵向泵浦理论,分析了X形谐振腔几何参数的确定条件和模式匹配条件;根据有关NaCl(OH^-):(F₂⁺)_H和KCl(Na⁺,OH^-):(F₂⁺)AH色心激光的主要研究结果,分析了提高色心激光输出效率的可能途径.     

质子化corroles的结构和电子光谱的密度泛函理论研究

用电子密度泛函理论研究了N-质子化corrole(H₄Cor⁺)和meso位芳基取代质子化corroles(H₄TPC⁺、H₄TpFPC⁺和H₄TdCPC⁺)的几何构型、内消旋反应机理以及电子光谱. 结果表明,这些化合物均有两种稳定构型(势能面极小),一个为C₂对称性的S1(最稳定构型),另一为C₁对称性的S2,其中S1的能量比S2低约15.8～18.5 kJ/mol.S1和S2的corrole环都呈现明显的面外扭曲变形. 手性S1的两个对映异构体之间的转化是一个以S2为中间态的多步过程. 用TDDFT计算了它们的紫外可见电子吸收光谱和圆二色谱(ECD). 与H₄Cor⁺相比,H₄TPC⁺、H₄TpFPC⁺和H₄TdCPC⁺的紫外可见吸收都发生了明显红移,且它们的Q带都因芳基取代基与corrole环之间的π-π共轭而明显增强. 计算表明,质子化corrole的若干相邻电子跃迁的旋转强度符号相反,表明ECD谱可能是研究其电子跃迁的有用工具.     

胸腺嘧啶低能量VUV光解离路径的实验和理论研究

利用同步辐射真空紫外光电离质谱和理论计算研究了胸腺嘧啶的光解离反应路径, 通过改变光子能量得到不同的质谱信号, 光子能量在12.0 eV时主要的碎片有m/z=98 (C₄H₆N₂₄O⁺)、97 (C₄H₅N₂O⁺)、84 (C₃H₄N₂O⁺或C<     

环戊酮光电离解离的实验和理论研究

本文介绍了真空紫外光电离质谱结合理论计算研究环戊酮单分子的光电离解离过程. 在9.0∽15.5 eV能量范围内，测量了环戊酮离子及其碎片离子的光电离效率曲线. 通过光电离效率曲线，将环戊酮分子的电离能确定为9.23±0.03 eV，并确认碎片离子为：C₅H₇O⁺，C₄H₅O⁺，C₄H₈⁺，C₃H₃O⁺，C₄H₆⁺，C₂H₄O⁺，C₃H₆⁺，C₃H₅⁺，C₃H₄⁺，C₃H₃⁺，C₂H₅⁺， C₂H₄⁺. 利用量子化学计算方法，在ωB97X-D/6-31+G(d,p)理论水平基础上，提出了C₅H₈O⁺的解离机制. 通过对环戊酮解离路径的分析，发现开环和氢迁移过程为环戊酮离子解离的主要路径.     

甲基环己烷在9∽15.5 eV能量区的真空紫外光电离研究

利用具有同步辐射源的反射式飞行时间质谱仪，研究甲基环己烷的真空紫外光电离和光解离. 观测到母体离子C₇H₁₄⁺和碎片离子C₇H₁₃⁺，C₆H₁₁⁺，C₆H₁₀⁺，C₅H₁₀⁺，C₅H₉⁺，C₄H₈⁺，C₄H₇⁺和C₃H₅⁺的光电离效率曲线. 测定甲基环己烷的电离能为9.80±0.03 eV，通过光电离效率曲线确定其碎片离子的出现势. 在B3LYP/6-31G(d)水平上对过渡态、中间体和产物离子的优化结构进行表征，并使用G3B3方法计算其能量. 提出主要碎片离子的形成通道. 分子内氢迁移和碳开环是甲基环己烷裂解途径中最重要的过程.     

氮化钒的选态双色可见紫外共振增强光电离和脉冲场光电子研究 (cited: 4)

对气态氮化钒(VN)分子在光子总能量为56900～59020 cm^-13∏0, v'=0)的单转动态, 然后再被紫外激光电离．这样的双色激光模式可以测量电子态、振动态和转动态都被选择和解析的氮化钒阳离子VN⁺(X²△; v⁺=0, 1, 2)光谱． 通过对转动解析的PFI-PE光谱模拟分析, 确定J⁺=3/2为基态离子态的最低转动能级, 从而确认VN⁺的基态电子态为²△_3/2．通过对VN+(PFI-PE)光谱的分析得到如下物理量的精确数值：VN⁺(X²△_3/2)的绝热电离能为IE(VN)=56909.5±0.8 cm^-1(7.05588±0.00010 eV),振动常数ω_e⁺=1068.0±0.8 cm^-1,反常振动常数ω_e⁺χ_e⁺=5.8±0.8 cm^-1;VN⁺(X²△_3/2)的转动常数B_e⁺=0.6563±0.0005 cm^-1,α_e⁺=0.0069±0.0004 cm^-1,平衡键长为1.529 ?;VN⁺(X²△_5/2)的转动常数B_e⁺=0.6578±0.0028 cm^-1,α_e⁺=0.0085±0.0028 cm^-1,平衡键长为1.527 ?;X²△_5/2,3/2自旋轨道耦合常数A=153.3±0.8 cm^-1     

金属氢超导性能的研究

 本文用强耦合超导理论研究了金属氢的一些超导性能，求出了具有超导性的金属氢的同位素效应值，热力学临界磁场，比热和T_c，H_c及Δ对有效声子谱α²F(ω)的泛函导数：dT_c/dα²F(ω)，dH_c/dα²F(ω)和d(2Δ/k_BT_c)/dα²F(ω)等与ω的关系曲线，说明超导性的一些参数与金属氢的电子-声子作用的关系。     

异戊二烯解离光电离理论研究

利用CBS-QB3理论计算方法研究了异戊二烯的可能解离通道.获得了主要碎片离子C₅H₇⁺,C₅H₅⁺,C₄H₅⁺,C₃H₆⁺,C₃H₅⁺,C₃H₄⁺,C₃H₃⁺的C₂H₃⁺的结构以及这些解离通道的解离能，并给出了相应的过渡态和中间体的结构和位垒.得到的异戊二烯电离势及主要碎片离子的出现势均与实验值符合的较好.最后，通过理论和实验结果的对比讨论了各通道的解离机理.     

锰氧化物团簇正离子与硫化氢反应的实验与理论研究 (cited: 2)

采用激光溅射法制备了同位素标记的氧化锰团簇正离子Mn_m¹⁸O_n⁺,并研究了其在快速流动反应管中与硫化氢在热碰撞条件下的反应,氧化锰团簇正离子与硫化氢反应前后的质量分布与强度变化由飞行时间质谱仪检测．实验表明,绝大多数氧化锰团簇正离子可与硫化氢发生氧-硫交换反应产生水分子,反应通式为：Mn_m¹⁸O_n⁺+H₂S→Mn_m¹⁸O_n-1S⁺+H₂¹⁸O．通过密度泛函理论计算了氧化锰团簇正离Mn₂O₂⁺、Mn₂O₃⁺和Mn₂O₄⁺与H₂S反应的机理,结果显示,在这些反应体系中氧-硫交换反应通道同时具有热力学和动力学优势,印证了实验中观察到的现象．气相团簇研究发现的氧-硫交换反应与相关凝聚相体系反应结果一致     

Complex dynamics of correlated electrons in molecular double ionization by an ultrashort intense laser pulse

With a semiclassical quasistatic model we achieve insight into the complex dynamics of two correlated electrons under the combined influence of a two-center Coulomb potential and an intense laser field. The model calculation is able to reproduce experimental data of nitrogen molecules for a wide range of laser intensities from the tunneling to the over-the-barrier regime, and predicts a significant alignment effect on the ratio of double over single ion yield. The classical trajectory analysis allows us to unveil subcycle molecular double ionization dynamics.     

Bifurcation of ion momentum distributions in sequential double ionization by elliptically polarized laser pulses

Using a fully classical model, we have studied sequential double ionization (SDI) of argon driven by elliptically polarized laser pulses at intensities well in the over-barrier ionization region. The results show that the width of the ion momentum along the major elliptical axis increases with the ellipticity while that in the laser propagation direction decreases with the ellipticity. The ion momentum in the minor elliptical axis bifurcates from one peak structure to three-peak, then to four-peak, finally to six-peak structure. Analysis shows that this ellipticity dependence of the ion momentum distribution is a result of the subcycle nature of the ionization dynamics in SDI. By changing the ellipticity and wavelength of the driving pulses, this subcycle ionization dynamics is more observable. This provides a simple and efficient way to study the subcycle ionization dynamics in strong field processes.     

Density oscillations in laser produced plasma decelerated by external magnetic field

This paper presents the dynamics as well as the stability of laser produced plasma expanding across the magnetic field. Observation of some high frequency fluctuations superimposed on ion saturation current along with structuring in the pin hole images of x-ray emitting plasma plume indicate the presence of instability in the plasma. Two type of slope in the variation of x-ray emission with laser intensity in the absence and presence of magnetic field shows appearance of different threshold intensity of laser corresponding to each magnetic field at which this instability or density fluctuation sets on. This instability has been identified as a large Larmor radius instability instead of classical Rayleigh-Taylor (R-T) instability.     

Dynamics simulation on interaction of intense laser pulses with atomic clusters

Under classical particle dynamics, the interaction process between intense femtosecond laser pulses and icosahedral noble-gas atomic clusters was studied. Our calculated results show that ionization proceeds mainly through tunnel ionization in the combined field from ions, electrons and laser, rather than the electron-impact ionization. With increasing cluster size, the average and maximum kinetic energy of the product ion increases. According to our calculation, the expansion process of the clusters after laser irradiation is dominated by Coulomb explosion and the expansion scale increases with increasing cluster size. The dependence of average kinetic energy and average charge state of the product ions on laser wavelength is also presented and discussed. The dependence of average kinetic energy on the number of atoms inside the cluster was studied and compared with the experimental data. Our results agree with the experimental results reasonably well.     

Spatial control of recollision wave packets with attosecond precision

We propose orthogonally polarized two-color laser pulses to steer tunneling electrons with attosecond precision around the ion core. We numerically demonstrate that the angles of birth and recollision, the recollision energy, and the temporal structure of the recolliding wave packet can be controlled without stabilization of the carrier-envelope phase of the laser, and that the wave packet's properties can be described by classical relations for a point charge. This establishes unique mapping between parameters of the laser field and attributes of the recolliding wave packet. The method is capable of probing ionic wave packet dynamics with attosecond resolution from an adjustable direction and might be used as an alternative to aligning molecules. Shaping the properties of the recollision wave packet by controlling the laser field may also provide new routes for improvement of attosecond pulse generation via high harmonic radiation.     

Effects of Atomic Coherence and Injected Classical Field on Chaotic Dynamics of Non-degenerate Cascade Two-Photon Lasers

Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.     

Effects of Atomic Coherence and Injected Classical Field on Chaotic Dynamics of Non-degenerate Cascade Two-Photon Lasers

Based on the cascade two-photon laser dynamic equation derived with the technique of quantum Langevin operators with the considerations of coherently prepared three-level atoms and the classical field injected into the cavity, we numerically study the effects of atomic coherence and classical field on the chaotic dynamics of a two-photon laser. Lyapunov exponent and bifurcation diagram calculations show that the Lorenz chaos and hyperchaos can be induced or inhibited by the atomic coherence and the classical field via crisis or Hopf bifurcations.     

激光场中一维和三维氢分子离子模型经典动力学行为的比较

应用经典轨迹方法,采用辛算法数值求解激光场中的一维和三维氢分子离子(H2 )的Hamilton正则方程,得到氢分子离子在激光场作用下的经典轨迹,并比较分析氢分子离子一维模型与三维模型的存活、解离、电离和库仑爆炸等动力学行为,以及电子的运动情况的相似之处.数值结果表明,采用一维模型能近似定性反映氢分子离子的动力学行为,并且简便可行.     

Peculiarities of the rotational dynamics of an ensemble of diatomic homonuclear molecules in a strong laser field

The rotational dynamics of an ensemble of molecules in a laser field has been studied. The results obtained within the framework of the quantum-mechanical and classical approaches have been compared. The features of the rotational dynamics connected with the non-classical character of the system have been described. It was taken into account that before the interaction with a laser pulse the ensemble was in a thermodynamically equilibrium mixed state. The case of an ultrashort laser pulse has been considered as well.     

辐射场的起伏对囚禁离子的量子相干性的影响

研究了囚禁离子与一随机相位的驻波场相互作用时的量子动力学行为,讨论了辐射场的起伏对囚禁离子的量子崩塌-回复特性的影响.对于相位扩散模型获得了这个问题的解析解.