Synthesis and Molecular Properties of Acceptor‐Substituted Squaraine Dyes

A broad series of more than 20 acceptor‐substituted squaraines was synthesized that feature different acceptor functionalities at the central squaraine four‐membered ring. The influence of these acceptor units on the reactivity of semisquaraine precursors and stability of the respective squaraines were explored. Thereby the dicyanovinyl group was found to be the most versatile acceptor group that enabled various modifications at the donor moiety of the squaraine scaffold, leading to an extended series of dicyanovinyl‐functionalized squaraines. The variation of donor units afforded a set of NIR fluorophores that cover a wavelength region from the visible at about 650 nm far into the NIR up to 920 nm with fluorescence quantum yields between 0.93 and 0.11 and outstanding optical brightness. This excellent optical property is related to a rigid molecular scaffold that is fixed in an all‐cis configuration by the additional dicyanovinyl acceptor unit. The change of the molecular symmetry from C_2h to C_2v upon functionalization of the squaraine core with dicyanovinyl acceptor group has been confirmed in solution by electro‐optical absorption (EOA) spectroscopy, revealing permanent ground‐state dipole moments μ_g in the range between 4.3 and 6.4 D. These dipole moments direct an antiparallel packing of the molecules in the solid state according to single‐crystal X‐ray analyses achieved for four dicyanovinyl‐functionalized squaraines. The structural properties, the EOA results, as well as the band shapes of the optical spectra indicate that these polymethine dyes are cyanine‐type chromophores. It is worth noting that the orientation of the dipole moment vectors is orthogonal to the orientation of the transition dipole moment vectors, which is an uncommon but characteristic feature of this rather novel class of polymethine dyes. With regard to applications of these dyes in organic solar cells, their redox properties were also studied by cyclic voltammetry.     

Ab initio investigation of the electronic and vibrational properties for the (CaLi)+ ionic molecule

A wide adiabatic study has been performed for numerous electronic states of CaLi⁺ molecular ion. The adiabatic potential energy curves and their spectroscopic constants (R_e, D_e, ω_e and T_e) have been calculated using an ab initio approach including a nonempirical pseudo-potential for the Ca and Li cores with the core polarisation potentials operator through full configuration interaction (FCI). Thereafter, the energies of vibrational levels and their spacing for all these states have been reported. In addition, the electric dipole moment curves have been investigated for the (1-19) Σ, (1-12) Π and (1-8) Δ electric states. Moreover it lets us check the extreme transition dipole moments (TDM). These behaviours of TDM are more accustomed to estimate the radiative lifetimes for all vibrational levels in 2¹Σ⁺ and 3¹Σ⁺ states. Also, the bound-bound and the bound-free contribution have been calculated precisely and by employing a Franck–Condon (FC) approximation.     

X-ray photoelectron spectroscopy and magnetism of Mn1−xAlxNi alloys

X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), magnetization and magnetic susceptibility of Mn_1−xAl_xNi alloys are reported. A change in the crystallographic structure takes place around x=0.4 from CuAuI to CsCl (B2) structure type. For x0.5 a mixed B2+L2₁ state exists which incorporates antiferromagnetic (B2) and ferromagnetic (L2₁) parts. A direct evidence for the existence of local moments on Mn sites in Mn_1-xAl_xNi alloys is given by the exchange splitting of XPS Mn 3s and Mn 2p3/2 core levels. The gradual filling of the Ni 3d band as the Al concentration increases can be explained by the hybridization of the Ni 3d band and Al 3sp states.     

Evolution of the N = 20 and N = 28 shell closures in neutron-rich nuclei

The isospin dependence of shell closure phenomena is studied for light neutron-rich nuclei within a microscopic self-consistent approach using the Gogny force. Introducing configuration mixing, ³²Mg is found to be dynamically deformed, although the N = 20 spherical shell closure persists at the mean-field level for all N = 20 isotones. In contrast, the N = 28 spherical shell closure is found to disappear for N - Z≥ 10 whereas deformed shell closures are preserved and lead to shape coexistence in ⁴⁴ S. Configuration mixing shows that the ground state of this nucleus is triaxially deformed. The first 2⁺ excitation energy E_x = 1.46 MeV and the reduced transition probability B(E2;0⁺ _gs→ 2⁺ ₁)= 420 e ² fm ⁴ obtained with our approach are in good agreement with experimental data. Received: 26 July 2000 / Accepted: 30 August 2000     

高能X射线聚焦组合透镜的理论研究

X射线聚焦组合透镜是一种利用折射效应对X射线辐射聚焦的新型元件。针对X射线波段的特性,综合考虑折射和吸收效应得出组合透镜的衍射屏函数,并利用衍射理论推导出X射线组合透镜的设计理论。利用统计学理论中一阶、二阶原点矩表征像面处的光学性能,使设计更简洁。该理论方法可方便地推广到双凹折射单元情况。通过数值计算分析了像向处强度分布的二阶中心矩以及焦点处辐射强度随组合透镜结构参最的变化关系,给出了一种铝基X射线组合透镜的结构参量设计结果。对于设计的组合透镜结构参量,计算了当X射线辐射能量分别为0．93 keV．9．89 keV和29．78 keV时,X射线辐射经过组合透镜后的焦点强度分布。     

Rayleigh–Ritz variation method and connected‐moments polynomial approach

We show that the connected‐moments polynomial approach proposed recently is equivalent to the well known Rayleigh–Ritz variation method in the Krylov space. We compare the latter with one of the original connected‐moments methods by means of a numerical test on an anharmonic oscillator. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Theoretical calculation of electron impact widths and shifts of XeII lines

Summary The shifts and widths of prominent XeII transitions are calculated in the semi-empirical approach; a very good agreement with experimental values is obtained. The oscillator strengths were calculated using complete intermediate coefficients after energy matrix diagonalization. The author of this paper has agreed to not receive the proofs for correction.     

Magnetic moments of hindered rotators by off‐center impurity ions

Off‐center impurity ions in solids often perform rotations around their regular lattice sites. Unlike quasifree rotors with rotational line spectra subject to textbook attention in quantum mechanics, the off‐center species are hindered rotors with spectra quantized in rotational bands. These bands occur because of tunneling through barriers arising along the orbital path. For an off‐center ion rotating along a planar orbit, such as the Li⁺ impurity nearest‐neighboring an F center in alkali halide, the hindered rotation will give rise to specific magnetic moments that couple to and quantize external magnetic fields normal to the orbital plane. We present a simple theory and estimates of Li⁺ magnetic dipoles and rotational bands to find conditions for an experimental verification. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Energy dependence of non-linear dynamical features in e^＋e^- collisions

A study of the d.ynamical fluctuation properties at various c.m.energies in e~ e~- collisions is performed using the Monte Carlo method.The results suggest that,after the normalized factorial moments of 3-dimensional phase space are analyzed using an isotropical phase space partition,the NFM describing non- linear dynamical properties show a power-law scaling,i.e.,the dynamical fluctuations in higher dimensional phase space are isotropic.For c.m.energies s~(1/2)≤80 GeV,the scaling exponentsφ_q increase rapidly with the c.m.energy and for c.m.energies s~(1/2)>80 GeV,theφ_q gradually saturate.