Channel switching effect in photodissociating N2O+ ion at 312.5 nm

A experimental observation is presented on the N2O+ photodissociation process, which exhibits a complete channel switching effect in a narrow energy range. The N2O+ ions, prepared at the X2Pi (000) state by (3+1) multiphoton ionization of neutral N2O molecules at 360.6 nm, were excited to different vibrational levels in the A2Sigma+ state in a wavelength range of 275-328 nm. Based on the estimates of total released kinetic energies from the time-of-flight mass spectrum, it was found that the dissociation pathway of N2O+ (A2Sigma+), NO+ (X1Sigma+) + N(4S) with lower dissociation limit, changes abruptly and completely to NO+ (X1Sigma+) + N(2D) with higher dissociation limit, in a excitation energy range of merely 250 cm(-1) at lambda approximately 312.5 nm. This phenomenon was explained by competition between the two dissociation pathways across the special excitation energy region.     

二氯甲烷同步辐射光电离的动力学研究

采用VUV同步辐射光源，在超声射流冷却条件下研究了二氯甲烷（CH2Cl2）光电离及其解离电离的动力学过程，测得CH2Cl2的电离能（IP）为11．32士0．01eV．通过对CH2Cl2光解离电离过程产生的碎片离子的出现势（AP）的测定，并结合有关中性分子的热力学数据，估算出该体系中有关离子的标准生成焓、中性分子和离子型分子中的键能及母体离子的解离能（DE）等一系列热力学数据．对CH2Cl2分子VUV光解离电离通道进行了细致的分析．     

A Characterization of the Standard Tori in C2 as Compact Lagrangian ξ-Submanifolds*

In this paper, the authors give a characterization theorem for the standard tori S¹(a) × S¹(b), a, b > 0, as the compact Lagrangian ξ-submanifolds in the two-dimensional complex Euclidean space C² , and obtain the best version of a former rigidity theorem for compact Lagrangian ξ-submanifold in C² . Furthermore, their argument in this paper also proves a new rigidity theorem which is a direct generalization of a rigidity theorem by Li and Wang for Lagrangian self-shrinkers in C².     

氮原子与卤代甲烷反应的直接氢抽提过程研究

利用B3LYP理论研究了N(~4S)+CH_3X(X = H, F, Cl)反应体系的直接氢抽提过 程,分别得到了各反应物、产物和过渡态的优化构型和谐振频率。同时应用了6- 31G(d), 6-311+G(d,p)和6-311+ + G(2d,2p)基组,考察其大小对反应体系中各物 种构型及能量的影响。理论计算表明,随着基组的增加,反应势垒逐渐降低,反应 吸热减少。对比取代甲烷的情形,结果表明反应过程中卤素原子具有典型的诱导效 应,降低了抽提势垒。     

四波混频过程中差频与和频的竞争研究

Tunable intense Vacuum Ultraviolet (VUV) laser was generated by two-photon resonant four wave difference frequency mixing (ω-=2ωUV-ωT) in Xenon. In the experiment some resonance attenuations of the VUV were observed at certain difference frequencies. These attenuations occur when the sum frequencies ω+=2ωUV+ωT coincide with excited ns (n=10,11) and nd (n=8~13) states. The third order linear susceptibility χ(3)（2ωUV+ωT;ωUV,ωUV+ωT） is reasonably increased by the double resonance enhancement, so the conversion efficiency of sum frequency mixing can be very high and the power of the pump laser is decreased and thus the difference frequency output is attenuated.     

Effect of Vibrational Angular Momentum on the Lifetime of CS21B2(1Σ)State

Predissociation lifetimes of totally 13 vibrational levels in the 1B2 state of jet-cooled CS2 have been determined by simulating the rotational band contours of the PHOFEX spectrum in the range of 209. 5 ～ 216 nm, where the PHOFEX spectrum was obtained by monitoring the laser-induced fluorescence of CS fragment via the Q band head excitation of（A 1Π,v' = 0）&（X 1Σ + ,v" = 0）transition. In order to investigate the influence of vibrational angular momentum quantum number K of the excited 1B2 （ 1Σ + U ）state,the nozzle was heated to increase the hot-band transition intensities. The results indicate that,for levels with the same vibrational quantum number but different K numbers in the 1B2 （ 1Σ + u ）state of CS2 ,the lifetime decreases with the increasing of quantum number K, suggesting that the dissociation could be accelerated by K number.     

射流冷却的OCS分子高分辨VUV吸收光谱研究

以双光子共振四波混频差频产生的高分辨、可调谐真空紫外激光(VUV)为光源,在151～156nm内测量了超声射流冷却的OCS分子1Σ+-1Σ+电子跃迁带的吸收光谱.由于采用射流冷却和高分辨激光,得到与前人吸收谱测量结果不同的光谱线线形,观察到两个呈现明显非对称结构的振动峰,通过Fano线型拟合,获得了这两个振动峰的半高峰宽和非对称参数q值,与前人光碎片激发谱测量结果基本一致.实验中,为了消除VUV激光强度波动的影响,通过记录参比光的方法,有效地提高了吸收光谱的信噪比,使得吸收测量的灵敏度达到1%左右.     

CS21B2(1Σ+u)态预离解产物CS的振转布居研究

用一束波长为 2 10 .2 7nm的激光将CS2 分子激发至预离解态1B2 (1Σ+ u) ,用另一束激光通过激光诱导荧光 (LIF)方法检测碎片CS ,在 2 5 0 .5～ 2 86 .5nm获得了CS碎片A1Π←X1Σ+ 振转分辨的激发谱 .通过对光谱强度的分析 ,获得了CS碎片v″ =0～ 8的振动布居和v″=1,4～ 8振动态的转动布居 .结果发现 ,碎片CS的振动布居呈双模结构 ,分别对应于CS2 分子1B2 (1Σ+ u)态的两个解离通道 ,即CS(X1Σ+ ,v″=0～ 9) +S(3 PJ)和CS(X1Σ+ ,v″ =0～ 1)+S(1B2 ) .由此得到两个解离通道的分支比S(3 PJ) :S(1B2 )为 5 .6± 1.2 .与前人 193nm处的研究结果相比 ,2 10 .2 7nm激发更有利于S(3 PJ)通道的生成 .此外 ,实验还发现CS的转动布居不满足热平衡分布 ,为两个Boltzmann分布的合成     

Minimal 2-spheresin S~n with Fixed Area

Ｍｉｎｉｍａｌ２┐ｓｐｈｅｒｅｓｉｎＳｎｗｉｔｈＦｉｘｅｄＡｒｅａＬｉＸｉｎｇｘｉａｏ（李兴校）（ＨｅｎａｎＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｘｉｎｘｉａｎｇ，Ｈｅｎａｎ，４５３００２）ＡｂｓｔｒａｃｔＦｏｒｍｉｎｉｍａｌ２－ｓｐｈｅｒｅｓＳ２ｉｎｔ...     

Extracellular Expression of L-Aspartate-α-Decarboxylase from Bacillus tequilensis and Its Application in the Biosynthesis of β-Alanine

Applied Biochemistry and Biotechnology - L-aspartate-α-decarboxylase was extracellularly expressed to enhance its production for β-alanine biosynthesis. L-aspartate-α-decarboxylase...