Excited electronic state calculations by the transcorrelated variational Monte Carlo method: application to a helium atom

We have implemented the excited electronic state calculations for a helium atom by the transcorrelated variational Monte Carlo (TC-VMC) method. In this method, Jastrow-Slater-type wave function is efficiently optimized not only for the Jastrow factor but also for the Slater determinant. Since the formalism for the TC-VMC method is based on the variance minimization, excited states as well as the ground state calculations are feasible. It is found that both the first and the second excitation energies given by TC-VMC are much closer to the experimental data than those given by the variational Monte Carlo method with using the Hartree-Fock orbitals. The successful results in the TC-VMC method are considered to be due to the nodal optimization of the wave functions.     

在发光二极管背光源上极具应用前景的Beta-sialon (Si6-zAlzOzN8-z):Eu2+窄带绿色荧光粉

基于氮化镓的白光发光二极管(LED)是目前一项崭新的背光源技术,广泛应用于宽色域、高光效的液晶显示屏。 在此项技术中,作为关键材料的荧光粉决定着背光单元的色域范围、发光效率和可靠性,因而要求它应具合适的发射波长和窄带发射。 β-sialon:Eu²⁺(sialon:silicon aluminum oxynitride(赛龙))就是一款非常适合背光应用的绿色荧光粉,这得益于其位于525~545 nm发射峰和只有55 nm狭窄的峰宽。 此文回顾和综述了β-sialon:Eu²⁺的合成方法、光谱特性、电子结构、晶体结构、可靠性和它的具体应用。 计算模拟和实验测试结果表明,Eu²⁺位于沿c轴方向的大孔道之中,并与6个最紧邻的(O,N)原子等距离配位。 因而,Eu²⁺的狭窄发射峰源自于Eu²⁺局域结构的高度对称性。 β-sialon:Eu²⁺的发射波长和带宽都能通过组成裁剪,即z值,进行调控;低z值组成能够实现更短波长发射和更窄带宽。 与传统的基于钇铝石榴石(YAG)荧光粉的背光源相比,β-sialon:Eu²⁺再搭配红色荧光粉制备的背光源具有更宽的色域,色域范围可提高15%以上。 其优异的发光性能和高可靠性使得β-sialon:Eu²⁺成为应用于先进显示屏的极其重要的绿色发光材料。     

Sequential Nucleophilic Substitution of Phosphorus Trichloride with Alcohols in a Continuous-Flow Reactor and Consideration of a Mechanism for Reduced Over-reaction through the Addition of Imidazole

We demonstrate a sequential nucleophilic substitution of highly electrophilic and inexpensive phosphorus trichloride with three different alcohols in a continuous-flow reactor. A variety of alcohols including ones that contained acid- and/or basic-labile functionalities were rapidly reacted. A over nucleophilic substitution that occurred during reaction of the second alcohol was suppressed by the addition of imidazole. Density functional theory calculations of the sequential nucleophilic substitutions of alcohols were performed both with and without imidazole, and Berry pseudorotation was suggested as a rate-limiting step in both cases. Herein, we discuss the reasons for the decreased selectivity in the absence of imidazole as well as those for improved selectivity in the presence of imidazole during the second nucleophilic substitution.     

Compensation for reconstructed image distortion using camera model with lens distortion in incoherent digital holography

Optical Review - In incoherent digital holography (IDH), the reconstructed image may be distorted owing to lens aberration, which degrades image quality. A conventional camera lens is designed such...     

Racemic Tartrate/Malate Anions Combine with Racemic Complex Cations to Form Optically Active Ionic Crystals

Spontaneous resolution has attracted continuing attention in various research fields since Pasteur's work on the crystallization behavior of racemic tartrate. Here, a unique example of this phenomenon is reported, involving ionic crystals generated from racemic RR/SS- tartrate or R/S-malate and racemic ΔΔ/ΛΛ-[Ag₃Rh₂(2-aminoethanethiolato)₆]³⁺ (ΔΔ/ΛΛ-[ 1 ]³⁺) in water. RR- and SS-tartrate selectively recognize the ΛΛ and ΔΔ isomers of [ 1 ]³⁺ to produce ionic crystals of (ΛΛ-[ 1 ])₂(RR-tartrate)₃ and (ΔΔ-[ 1 ])₂(SS-tartrate)₃, respectively, which can undergo spontaneous resolution. While spontaneous resolution also occurs when using R/S-malate, R- and S-malate select the opposite isomers of [ 1 ]³⁺ to give ionic crystals of (ΔΔ-[ 1 ])₂(R-malate)₃ and (ΛΛ-[ 1 ])₂(S-malate)₃, respectively. In the presence of S-aspartate, (ΛΛ-[ 1 ])₂(R-tartrate)₃ and (ΔΔ-[ 1 ])₂(S-tartrate)₃ are preferentially crystallized from ΔΔ/ΛΛ-[ 1 ]³⁺ and RR/SS-tartrate at solution pH values of 6 and 10, respectively. This finding provides significant insight into the optical resolution of chemical species by spontaneous resolution and the origin of homochirality in nature.     

Use of state of polarization transparent scheme for polarization shift keying signal as optical phase conjugator to improve the transmission performance

Transmission characteristics of polarization shift keying (PolSK) signal is experimentally demonstrated in this work. Performance degradation due to transmission is improved using optical phase conjugation (OPC) technique. The wavelength converter based on the proposed state of polarization (SOP) transparent scheme for PolSK signal is effective to use it as mid-link optical phase conjugator and which is difficult to achieve using conventional wavelength conversion scheme. It is found that for fiber transmission, the performance of both of the orthogonal SOPs of the PolSK signal is different for their respective chirping characteristics which can be optimized to be similar using proposed OPC technique.     

Synthesis and properties of some novel high birefringence phenylacetylene liquid crystal materials with lateral substituents

We have synthesized and investigated new 3-ring phenylacetylene liquid crystals with high birefringence values (Δn) to improve the nematic temperature range while retaining a high optical anisotropy. In the case of modifying the terminal ring, the introduction of branched alkoxy chains, fluorine or methyl groups shifted the nematic phase to lower temperatures. In order to minimize the influence of the substituent on Δn, the incorporation of lateral methyl groups was chosen as the most profitable method for obtaining wide and low temperature nematic phases. With these results in mind, we studied the effect of the position of the methyl group on the physical properties. The most effective methyl position for improving the nematic temperature range was on the central ring. From the standpoint of obtaining high Δn values and low viscosity, the central ring was also the best position.     

A novel partitioning process for treatment of high level liquid waste using macroporous silica-based adsorbents

To separate the long-life and significant fission product elements from high level liquid waste (HLLW), a novel partitioning process for the treatment of HLLW has been studied experimentally based on column separation technique using macroporous silica-based adsorbents. This process consists of (1) Cs and Rb are removed by the first separation column packed with (calix[4] + dodecanol)/SiO₂–P adsorbent; (2) Sr and Ba are eluted out by the second separation column packed with (DtBuCH18C6 + dodecanol)/SiO₂–P adsorbent; (3) Pd is partitioned by the third separation column packed with MOTDGA–TOA/SiO₂–P adsorbent; (4) Ru, Rh and Mo can be separated by the fourth separation column packed with TODGA/SiO₂–P adsorbent; (5) Am is separated from RE by the fifth column is packed with isobutyl-BTP/SiO₂–P adsorbent. The experimental results indicated that this partitioning process is essentially feasible.