亚稳Ar(~3P_(0.2))原子与NH_3分子碰撞传能分解动力学研究

本文利用流动余辉技术研究了亚稳态Ar(~3P_(0,2))原子与多原子NH_3分子的碰撞传能过程.实验得到了碰撞解离产物NH分子初生态A~3Ⅱ和C~1Ⅱ的振动和转动分布;首次测得了产物分子N_2(C~3Ⅱ_u)的相对振动布居及其生成速率常数.     

转动传能中NH2()精细结构态变化的研究

利用高分辨光谱技术他NH2（A~2A1,090)423(F1/F2) 在单次碰撞条件下的精细态色散光光谱,发现NH2（A~2A1)在与团壳层分子碰撞传能过程中,母能级的自旋－转动耦合守恒,从实验上直接证实了在开壳层－ 壳层分子碰撞过程中电子自旋为一旁观者的假设;由于长程作用力造成子能级有保持原来自旋－转动耦合的倾向。     

碰撞诱导振动能量转移：Cs2[B1∏u(v′=5)]+ N2→Cs2[B1∏u(v′=4，6)]+ N2

利用激光诱导荧光方法研究了Cs2[B1∏u(v′=5)]与N2的碰撞能量转移。脉冲激光激发Cs2基态至[B1∏u(v′=5)]态,池温保持在410K ,N2气压在1.5×102Pa至2.5×103Pa之间变化。荧光中含有直接荧光和碰撞转移荧光成分,记录直接荧光B1∏u(v′=5)→X1∑+g(v〞=0)的时间分辨强度。从荧光强度的对数值给出的直线斜率得到B1∏u(v′=5)→X1∑+g(v〞=0)的有效寿命,由Stern-Volmer方程,得到B1∏u(v′=5)→X1∑+g(v〞=0)的辐射寿命为（45±9）ns。B1∏u(v′=5)态与N2碰撞的猝灭总截面为（9.8±1.5）×10-15cm2。用类似的方法得到B1∏u(v′=4,6)能级的辐射寿命。在不同的N2气压下,测量B1∏u(v′=5,4,6)→X1∑+g(v〞=0)的时间积分荧光强度,首次得到v′=5→v′=4及v′=5→v′=6的碰撞转移截面分别为(3.9±0.8)×10-15cm2和(4.1±0.8)×10-15cm2。     

转动传能中的量子干涉--干涉角和转动量子数的关系

沙国河等人在CO(A1∏(v=0)~e3∑-(v=1))体系与He,Ne和Ar碰撞诱导转动传能中首次观测到了量子干涉效应,并测量了干涉度。从理论上进一步研究原子-双原子分子体系碰撞诱导转动传能中量子干涉效应与转动量子数以及能量间隔的关系是十分必要的。我们考虑长程相互作用势,应用一级玻恩近似和直线轨迹近似,分别计算了CO(A1∏(v=0)~e3∑-(v=1))体系和He,Ne,Ar碰撞诱导转动传能中不同转动量子数以及不同能量间隔下的干涉角,得到了干涉角随转动量子数和能量间隔的变化趋势。这些结果对设计、分析这种类型的实验有一定的指导意义。     

Cs(6D5/2)+H2→CsH[ X1Σ+(v,J)]+H转动分辨总截面的测量

利用泵浦-检测方法,在样品池条件下,研究了Cs(6D5/2)与H2反应碰撞传能过程。利用激光感应荧光（LIF）光谱技术,确定了CsH[X1Σ+(v,J)]振转能级上的布居分布,转动态分布与热统计分布基本一致.Cs激发态原子密度由激光能量吸收得到.记录A1Σ+(v',J+1)→X1Σ+(v,J)的时间分辨荧光,从荧光强度的对数值给出的直线斜率确定(v',J+1)→(v,J)的自然辐射率,结合(v,J)→(v',J+1)吸收系数的测量,得到反应生成物CsH[X1Σ+(v,J)]态的分子密度.由速率方程分析,给出反应截面(v,J),对J求和,得到(v)[10-16cm2单位]分别为（0.64±0.19）（v=0）和（0.58±0.17）（v=1）.     

反应物NO的振动激发对反应C(3P)+NO(X2Π)→CO(X1Σ+)+N(2D)立体动力学性质的影响

采用准经典轨线方法研究碰撞能为0.23 eV时,反应物分子NO在不同初始振动态(v=0～3)下发生在两个电子态(2A″和2A′)势能面上反应C(3P)+NO(X2Π)→CO(X1Σ+)+N(2D)的立体动力学性质.计算反应产物的转动角动量矢量分布(P(θr)和P(?r))以及微分散射截面(P00(ωt),(P)20(ω...     

Na2(A1∑+u，v=8~b3Π0u，v=14)-Na体系碰撞诱导转动传能的微分干涉角

对原子-双原子体系碰撞诱导转动传能进行了进一步的理论研 究. 在含时一级波恩近似的基础上考虑各向异性相互作用势，计算了 单-叁重混合态的Na2(A1∑+u，v=8~b3Π0u，v=14)体系与Na碰撞 的微分干涉角(b·?和b??)，得到了微分干涉角与碰撞参数的关系，对 其碰撞量子干涉作出了定量准确的描述.     

Na2(A1∑u+,v=8～b3Ⅱ0u,v=14)-Na体系转动传能的碰撞量子干涉效应

沙国河及其工作组于1995年发表了CO A1Π(v=0)～e3∑-(v=1)与He1,Ne及其它碰撞伴的碰撞过程中转动传能的碰撞量子干涉现象,并得到了积分干涉角,陈等从理论和实验上发现了Na2(A1∑u ,v=8～b3Π0u,v=14)体系与Na(3s)碰撞的碰撞量子干涉现象,孙等计算了其积分干涉角,但是对微分干涉角没有过多的计算.本文作为对原子-双原子体系碰撞诱导转动传能的进一步理论研究,在含时一级波恩近似的基础上考虑各向异性相互作用势和长程相互作用势,计算了单叁混合态的Na2(A1∑u ,v=8-bΠ0u,v=14)体系与Na碰撞的微分干涉角,并得到了微分干涉角与碰撞参数的关系,此理论模型对理解和进行分子束实验是非常重要的.     

Collision-induced Rotational Energy Transfer in an Atom-Diatom System

通过对原子-双原子体系碰撞诱导转动传能的理论研究,在含时一级波恩近似的基础上考虑各向异性相互作用势和长程相互作用势,计算了单叁混合态的CO A1Ⅱ(v=0)～e3∑-(v=1)和He、Ne、Ar碰撞的微分干涉角,并得到了微分干涉角与碰撞参数的关系.     

K(5P)与H2的反应碰撞和电子-振动能量转移

K(5P)与H2反应生成KH(v′′=0-3)振动态,测量了各振动态的转动分布,转动玻尔兹曼温度为455K,而振动温度为1604K,这个接近池温的转动温度和很高的振动温度是共线碰撞机制的有力证据.利用高分辨率瞬时吸收技术得到各振动能级上转动态的布居分布,从而得到反应碰撞转移速率系数,对于v′′=0、1、2、3,分布别为(3.45±0.86)×10-13、(1.35±0.34)×10-13、(6.28±1.57)×10-14和(2.35±0.59)×10-14cm3s-1. 同时研究了K(5P)-H2的电子-振动能量转移,利用相干反斯托克斯拉曼散射（CARS）探测H2的振动态分布.扫描CARS谱发现v=1、2、3上有布居. 由CARS峰值得到H2（0,1）、（1,1）、（2,1）、（3,1）和（3,3）布居之比. H2(0,1)布居由450K的转动分布得到,因而得到（1,1）、（2,1）、（3,1）和（3,3）态的布居,从而获得K(5P)-H2(1,1)、（2,1）、（3,1）和（3,3）的电子-振转速率系数分别是（1.1±0.3）×10-13、（9.3±2.5）×10-14、（4.2±1.1）×10-14和（3.8±1.0）×10-14cm3s-1.     

氨团簇(NH3)2的异构化研究

本文在密度泛函理论的基础上,利用B3LYP/6-31G(d)方法研究了(NH3)2的两种同分异构体2a和2b之间的异构化过程,结果表明由2a异构化到2b要跨过1.39kcal/mol的反应势垒,而从2b异构化到2a的反应势垒为0.606kcal/mol.     

Phase Transition in the Compound NH3(CH2)5NH3TlCl5

Penthylene diammonium pentachlorothallate(III) exhibits a phase transition at 316 K <artwork name="GPHT21157eu1"> This transition has been characterized by optical birefringence, dielectric measurements differential scanning calorimetry and spectroscopic measurements on polycrystalline samples. The space group and the cell parameters of phase I were determined by X-ray diffraction from single crystals. Phase I has space group P2₁2₁2₁, with Z = 4, a = 7.696(3), b = 13.2890(17) and c = 13.503(18) Å. The transition is both displacive and order-disorder involving mainly conformational changes of the organic chain [NH₃(CH₂)₅NH₃]²⁺ coupled with distortion of the TlCl₆ octahedra. This behaviour and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds.     

A shock-tube study of NH3 and NH3/H2 oxidation using laser absorption of NH3 and H2O

Ammonia (NH₃) is an attractive carbon-free fuel, yet its low reactivity presents many challenges for direct use in combustion applications. These combustion challenges could be resolved by mixing NH₃ with more reactive fuels such as hydrogen (H₂). To further contribute to NH₃ and NH₃/H₂ kinetics—which arguably still requires much improvement—new experiments were conducted over a wide range of temperatures (1474–2307 K), near-atmospheric pressure, several NH₃/O₂ mixtures (equivalence ratios varying from 0.56 to 2.07), and near-stoichiometric NH₃/H₂/O₂ mixtures with NH₃:H₂ ratios of 80:20 and 50:50. During these experiments, laser absorption diagnostics near 10.4 µm and 7.4 µm were simultaneously employed to measure NH₃ and H₂O time histories, respectively. Characteristic parameters, such as NH₃ half-life time and H₂O induction delay time, were extracted from the time-history profiles, and these parameters present stringent speciation targets for mechanism validation. After an assessment of most modern kinetics models, three, most accurate, mechanisms were compared against the experimental results. Only one model was able to partially reproduce the pure NH₃ experiments, yet none of the models were capable of predicting the NH₃/H₂ experiments. Reaction pathway analysis showed that NH₃ oxidation proceeds via forming NH₂ then followed three different routes to form N₂. Importantly, the models considered showed different levels of importance for each route. Sensitivity analysis showed that the NH₃/H₂ experiment is mostly sensitive to NH₃+OH⇄NH₂+H₂O. Interestingly, this reaction showed no sensitivity for the NH₃/O₂ experiments. Overall, the models exhibited significantly slower reactivity than the NH₃/H₂ experiments, and the kinetics analysis showed that the start of this reactivity is governed by the levels of H-atoms in the early stages of the experiments. At these early stages of the experiments, propagation and branching reactions in the H₂/O₂ system are the main contributors to generating H radicals, along with the reaction NH₃+H⇄NH₂+H₂ which proceeds in its reverse direction.     

81Br NQR Study of [NH3(CH2) n NH3]CdBr4 (n = 4 and 5) and [NH3(CH2) n NH3]ZnBr4 (n = 5 and 6)

⁸¹Br NQR frequencies and differential scanning calorimetry (DSC) were measured as a function of temperature. [NH₃(CH₂)₄ NH₃]CdBr₄ (1) and [NH₃(CH₂)₅NH₃]CdBr₄ (2) showed a doublet and quartet ⁸¹Br NQR spectrum, respectively. [NH₃(CH₂)₅NH₃]ZnBr₄ (3) and [NH₃(CH₂)₆NH₃]ZnBr₄ (4) exhibited a four-line ⁸¹Br NQR spectrum. From the NQR results, it is inferred that (1) and (2) consist of infinite two-dimensional sheets of corner-sharing CdBr₆ octahedra, whereas (3) and (4) have isolated [ZnBr₄]²⁻ tetrahedra. All of the crystals except (1) showed at least one structural phase transition above 380 K.     

Optical properties of the proton conductor (NH2(CH3)2)2CoCl4

Based on the data from optical-spectral studies of (NH₂(CH₃)₂)₂CoCl₄ crystals, the existence of high-temperature phase transitions at 419, 380, 352, and 313 K is confirmed. It was shown that with the exception of the first transition, they are related to a considerable extent to rearrangement of the network of hydrogen bonds and are not accompanied by, considerable deformation of the lattice. In this connection the character of the electron-phonon interaction remains unchanged in the entire temperature range of the measurements. The (NH₂(CH₃)₂)₂CoCl₄ structure at room temperature is close to that of the ordered low-temperature phases of such isomorphous crystals as β-K₂SO₄. I. Franko State University, L’vov, Ukraine, 8, Kirill and Mefodii St., UA-290005, L’vov. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 412–418, May–June, 1998.     

Structural phase transition in elpasolite-like (NH4)2KWO3F3

A new chemical compound, (NH₄)₂KWO₃F₃, was synthesized. The Rietveld-refined crystal structure was found to be cubic at room temperature and to belong to the elpasolite family (space group ). The heat capacity and unit cell parameters were studied within a broad temperature range. A second-order phase transition was found to occur at 235.4 K and to be well described in terms of phenomenological theory. Hydrostatic pressure broadens the temperature interval of stability of the cubic phase (dT₀/dp = −10.8 K GPa⁻¹). A possible model of structural ordering based on a comparison of the entropy parameters and electron density distribution in oxygen and fluorine atoms is discussed.     

Magnetic transitions in NiBr2 6NH3 and NiCl2 6NH3 up to 75 koe

The field dependence of the magnetic susceptibility of powdered NiBr₂ 6NH₃ and NiCl₂ 6NH₃ was measured up to 75 koe at temperatures above and below T_N. The anomalies found are discussed in terms of other magnetic data known for these salts.     

Vibrational Spectra of Cd(NH3)2Cl2 with 2H Isotopic Substitution

The infrared and Raman spectra of the cadmium diammindichloride complexes with ²H isotopic substitution, have been measured. A normal coordinate analysis for the isotopic compounds has been carried out based on a Local Symmetry Force Field (LSFF). The results sup port the experimental assignments.     

Magnetic susceptibility of the compound (CH2)10(NH3)2FeCl4

The magnetic susceptibility of the compound (CH₂)₁₀(NH₃)₂FeCl₄ is measured in the temperature range from liquid nitrogen temperature up to room temperature. The effect of thermal and magnetic history on the data obtained is also discussed. It is shown that the compound is antiferromagnetic with a Néel temperature of 93 K but it appears that the antiferromagnetic intra-layer exchange interaction co-exists with a weak ferromagnetic interlayer interaction.     

Optical studies of the ferroelastic phase transitions in Rb3H(SeO4)2, (NH4)3H(SO4)2 and (NH4)3H(SeO4)2

Optical observations of growth twins and ferroelastic domains and measurements of the rotation of the optical indicatrix were carried out for Rb₃H(SeO₄)₂ and (NH₄)₃H(SO₄)₂ using an optical microscope. Taking into account the symmetry reduction from the rhombohedral (Rm) to the monoclinic phase (B2/a) the occurrence of domains and growth twins can be well described. The orientations of oblique ferroelastic walls are well determined by the spontaneous strains ^s e ₁₁ and ^s e ₂₃ at room temperature.