Vibrational relaxation and electronic mutation of metastable nitrogen molecules generated by nitrogen atom recombination on cobalt and nickel

The recombination of nitrogen atoms on polycrystalline samples of cobalt and nickel produces metastable electronically excited nitrogen molecules, probably N₂(W³Δ_u), which are collisionally transferred to the N₂(B³Πg) state. Information about vibrational relaxation of the metastable state by N₂(X¹Σ⁺_g) is inferred from composition dependent changes in the observed first positive emission spectrum [N₂9A³Σ⁺_g)−N₂(B³Π_g] with the aid of multilevel, steady-state, kinetic model.     

Vibrational relaxation in liquid nitrogen

The time constant for the collisional deactivation of the υ = 1 vibrational level of N₂ is found to be 1.5 ± 0.5 s in liquid nitrogen of 99.9995% purity of 78 K. This result is consistent with a simple binary collision theory of vibrational relaxation for liquids.     

Solvent effects on non-resonant vibrational deactivation: N2(ν = 1) deactivated by CH4 in liquid Ar/liquid N2 mixtures

New measurements have been made of rate constants for the vibrational deactivation of N₂(ν = 1) by CH₄ in liquid Ar/liquid N₂ mixtures. The ratio of the liquid phase rate constants, k_L,M for the liquid mixture over k_L,Ar for liquid argon solution, varies non-linearly with composition. The results imply a saturation effect which occurs when one solvent N₂ molecule is present in the first solvation shell of the excited molecule. It is proposed that this is due to the formation of a N₂(ν = 1) … N₂ collision complex.     

褐煤中有机氮的赋存形态分布和分子结构特征

利用X射线光电子能谱(XPS)分析了先锋褐煤(XL)、小龙潭褐煤(XLT)和胜利褐煤(SL)及其萃取残渣表面有机氮的形态分布。结果表明,三种萃取残渣表面五种有机氮的含量分布各异,但均以吡咯型氮为主。考察了在300℃下Na OH催化的褐煤萃取残渣的超临界甲醇解反应,XL、XLT和SL萃取残渣超临界甲醇解所得石油醚可溶物的收率分别为46.0%、43.8%和47.6%(质量分数)。用傅里叶变换离子回旋共振质谱(FTICR/M S)分析石油醚可溶物中的含氮化合物(NCCs)。结果表明,NCCs主要包括N_1、N_1O_1-N_1O_5、N_2、N_2O_1-N_2O_4、N_3O_2和N_5O_2-N_5O_4类化合物。根据不饱和度和碳原子数的分布推测了NCCs的分子结构特征,表明绝大部分NCCs含羟基和羧基等含氧官能团,氮原子主要以吡咯、吡啶和氨基的形式存在于芳环结构中,以1-3个芳环的结构为主。褐煤中的-C-O-桥键的断裂是生成NCCs的一个重要路径。     

N2O+离子B2П态的光谱与光解离动力学

用一束波长为360.55 nm的激光直接作用于超声射流的N₂O分子束, 通过(3+1)共振增强多光子电离(REMPI)过程制备纯净的N₂O⁺(X²П(0,0,0))母体离子, 再用另一束波长在243-278 nm范围的激光将母体离子激发至B²П态后解离. 扫描解离激光波长, 监测NO⁺离子碎片的强度, 从而获得N₂O⁺离子B²П态的光致碎片激发(PHOFEX)谱. 通过拟合转动分辨光谱, 得到了相应的转动常数和自旋分裂常数, 从而区分了A²Σ⁺态高振动能级和B²П态带源的贡献, 明确了N₂O⁺离子B²П态的光谱"带头"位置(37154 cm^-1), 并将获得的振动光谱初步归属为B²П(v₁,v₂,v₃)←X²П的振动跃迁序列. 通过对NO⁺碎片离子的飞行时间质谱峰形的分析, 还获得了解离过程中释放的平均平动能, 并结合电子激发态势能面, 讨论了N₂O⁺离子B²П态的解离机理.     

先锋褐煤可溶有机质中含氮化合物的组成和结构特征

先锋褐煤在高压釜中用等体积的甲醇/甲苯溶剂300℃下热溶得到热溶物和热溶残渣,利用X射线光电子能谱（XPS）分析了先锋褐煤及其热溶残渣中氮的形态,利用气相色谱/质谱（GC/MS）和电喷雾傅里叶变换-离子回旋共振质谱（ESI FT-ICR MS）分析了热溶物中含氮化合物的组成和结构特征。研究表明,先锋褐煤中氮形态含量顺序为季氮 > 吡啶氮 > 吡咯氮,而季氮在热溶过程中更易溶出。GC/MS共检测出热溶物中20种含氮化合物,并且大部分为胺类化合物。ESI FT-ICR MS检测出热溶物中300多种含氮化合物,大部分含氮化合物含一个或三个氮原子。含一个氮原子的含氮化合物主要以N₁O₁、N₁O₂和N₁O_xS_1-2类化合物为主,而含三个氮原子的含氮化合物主要以N₃O_xS_1-2（x=1-12）类化合物为主。含一个氮原子的含氮化合物的等效双键数和碳数随氧原子数增加而增加。     

Lifetime measurements of the excited states of N2 AND N2 by laser-induced fluorescence

Absorption and fluorescent scattering of nitrogen laser radiation by a low-pressure RF laboratory plasma (n_e = 10¹² cm⁻³) has been observed for the first negative system of N₂⁺. A 67±1 ns lifetime of N₂⁺ (B ²Σ_u⁺) was experimentally measured from the laser-induced fluorescence. In addition, enough collisionally excited N₂ (B ³Π_g) was produced to observe laser-induced fluorescence for the second positive system of N₂. The lifetime of N₂ (C ³Π_u) was found to be 41±2 ns. The measured lifetimes are in good agreement with published values calculated from theory.     

The interaction of formohydroxamic acid with nitrogen: FTIR matrix isolation and ab initio studies

Argon matrix infrared spectra of the complexes formed between formohydroxamic acid, HCONHOH (FHA) and nitrogen have been recorded. The experimental results indicate formation of two isomeric complexes in which the nitrogen atom of the N₂ molecule is attached to the NH or OH groups of FHA. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the MP2 level with the 6-311++G(2d,2p) basis set. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data.     

Vibrational disequilibrium in a low-pressure Na-Catalyzed CO---N2O Flame

A high-resolution emission spectrum of a low-pressure Ar-diluted CO + N₂O → CO₂ + N₂ flame catalyzed by Na metal vapor has been obtained and examined for vibrational disequilibrium. Emission in the 1900-2400 cm⁻¹ spectral region, which includes the fundamental and “hot” bands of CO, CO₂(ν₃), and N₂O(ν₃), was recorded with high resolution and the CO emission was analyzed in detail to determine vibrational and rotational temperatures which were found to be unequal, T_v = 2050°K and T_R = 1100°K. An examination of vib-vib and vib-trans energy transfer mechanisms results in the conclusion that an excess of 14% of the chemical energy is preferentially deposited in the resonantly-coupled N₂, CO, CO₂ (ν₃), and N₂O(ν₃) vibrational modes. It is further observed that CO vibrational levels for ν > 4 are excessively populated, presumably due to quenching of Na*(3p) by CO; the flame is accompanied by intense Na D-line chemiluminescence.     

Raman spectroscopy on high-pressure fluids of molecular oxygen and nitrogen

High-pressure Raman scattering experiments of O₂ and N₂ were carried out at 296 K and at pressures up to 10 and 6 GPa, respectively, and the pressure dependence of vibrational spectra of O₂ was studied on the basis of molecular interactions in comparison with N₂. An appreciable contribution of the attractive interaction to the vibrational frequency was observed for fluid O₂. The linewidth of the spectra for fluid O₂ showed a sharp increase with increasing pressure, and the fluid–solid transition was observed at 5.9 GPa with a sudden drop of the linewidth.     

Angular distributions of N2 in the photodissociation of N2O adsorbed on a partially oxidized Si(100) surface at 95 K

The time-of-flight distributions of the N₂ photofragment produced in the UV photodissociation of N₂O adsorbed on a partially oxidized Si(100) surface at 95 K have been measured as a function of the desorption angle. Photoinduced electron transfer initiates the dissociation of N₂O to produce an adsorbed oxygen atom and energetic N₂ desorbing from the surface. Interestingly, the angular distribution of N₂ originating from chemisorbed N₂O molecules is peaked at ≈ 32° from the surface normal. The results are discussed on the basis of bonding geometry and photodissociation dynamics of N₂O.     

FTIR studies of the CH3CN–BF3 complex in solid Ar, N2, and Xe: Matrix effects on vibrational spectra

FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N₂ and Xe matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several significant vibrational bands were also observed in N₂ and Xe. The observed frequency shifts on complexation, Δν, were qualitatively in good agreement with the computational results, which were calculated at the B3LYP/6-311++G(d,p) level using the optimized geometry of the C_3v eclipsed conformation. The observed magnitudes of Δν for most of the complex bands were larger than the calculated values. The BF₃ symmetric deformation mode is an exception. The observed frequency shits for this mode were smaller than the calculated values, especially in N₂. This suggests that even an inert matrix can significantly affect the vibrational spectrum of the complex.     

A CASSCF/icMRCI study of the electric field gradient in low-lying electronic states of N2/N2

The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X²Σ_g⁺ and B²Σ_u⁺ electronic states of the nitrogen molecule cation using the internally contracted multireference configuration interaction (icMRCI) method. The EFG’s and potential energy functions (PEF’s) are used to estimate the ¹⁴N nuclear quadrupole coupling constants (NQCC’s) in the two electronic states as functions of vibrational and end-over-end rotational quantum numbers. The dependences of the computed constants on the basis set and reference configuration space are investigated. Since no counterpart for comparison of the calculated NQCC’s exists, the N₂⁺ results are supported by analogous calculations on the X¹Σ_g⁺ and A³Σ_u⁺ states of N₂, for which established data are available. The overall good quality of the icMRCI wave functions is further corroborated by a favorable agreement of spectroscopic constants derived from the corresponding PEF’s and experimental data. Variations of the EFG with internuclear separation are explained in terms of wave function composition, and used for gaining specific insight into the chemical bonding in N₂⁺ and N₂.     

A comprehensive computational study of N2H–XH, N2H–X2, and N2H–XY(YX) (X=Y=F, Cl, and Br) proton bound complexes

The results of theoretical studies on structures and energetics are presented for proton-bound complexes N₂H⁺–XH, N₂H⁺–X₂, and N₂H⁺–XY(YX) (X=Y=F, Cl, and Br). In all the monocations complexes, the halogen atom shares a proton with N₂. The calculated energetic results show that the stability decreases when descending in the corresponding periodic table column. The possible proton transfer dissociation processes of N₂H⁺+XH, N₂H⁺+X₂, and N₂H⁺+XY systems into XH₂⁺, X₂H⁺, XYH⁺, and YXH⁺ and molecular N₂ are calculated to be endothermic for share of the processes. The NBO results show that the largest intermolecular charge transfer is found in the Br bonded complexes.     

The chemical production of electronically excited states in the H/NF2 system

A mixture of NF₃ and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF₂. When H₂, D₂, or CH₄ are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH₃. The latter free radicals can react with NF₂, probably by an elimination reaction to produce electronically excited NF: NF₂(²B₁) + H(D, CH₃) → HF^*(DF^* + NF(a¹Δ). A vibrational-to-electronic energy transfer process between the products of this reaction then produces the next higher state of NF: HF(ν 2) + NF(a¹Δ) → HF(ν−2) + NF(b¹Σ⁺). A similar transfer process has also been found between the electronically excited a¹Δ states of O₂ and NF: O₂(a¹Δ) + NF(a¹Δ) → O₂(X³Σ⁻) + NF(b¹Σ⁺). The H or D atoms but not the CH₃ radicals are then found to react with either NF(a¹Δ) or NF(X³Σ⁻) to produce electronically excited N(₂D) atoms, which in turn react with the NF(a¹Δ) molecules to produce N₂(B³Π_g). The observed nitrogen first positive radiation has been demonstrated to be produced entirely by this reaction mechanism rather than by the N(⁴S) recombination that accounts for the Rayleigh afterglow. In addition, the occurrence of the reaction N(₂D) + N₂O → NO(B²Π_r) + N₂ (X¹Σ⁺_g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A³Π), which has not been previously reported.     

Determination des constantes de dissociation ionique du chlorure de nitrosyle et de N2O4 dans le sulfolane

Determination of the ionic dissociation constants of nitrosyl chloride and dinitrogen tetroxide in sulpholane.

A silver chloride—silver electrode is used to study electrochemical systems involving nitrosyl chloride and dinitrogen tetroxide in sulpholane: Ag↓ + NOCl AgCl↓ + NO⁺ + e^- and Ag↓ + NOCl + NO^-₃ AgCl↓ + N₂O₄ + e^- The dissociation constants of these two NO⁺ donors determined in this way are: K_(NOCl) = 10^-11.8 mol l^-1 and K_(N2O4) = 10^-7.2 mol l^-1. A titration of N₂O⁴ solutions alone or in the presence of nitric acid is described. This titration is possible in mixtures which contain up to 90% (w/w) nitric acid.     

溴代烷烃与活性氮的反应发光研究

在流动余辉装置上, 利用N₂空心阴极放电制备活性氮, 研究了活性氮与溴代烷烃(CHBr₃、CH₂Br₂、C₂H₅Br、C₄H₉Br) 反应的化学发光.上述所有反应中, 在550～750 nm波段均观察到了较强的NBr (b¹Σ+→X³Σ^-)跃迁发射谱. 同时在活性氮与CHBr₃和CH₂Br₂的反应中, 在流动管下游还观察到了CN (A²π, B²π→X²Σ⁺)的发射谱. 验证性的实验表明, 激发态NBr (b¹Σ⁺)是由二步过程形成: N(⁴S)与溴代烷烃反应生成NBr (X³Σ^-), 再通过N₂ (A ³Σ_u⁺)分子能量转移到激发态NBr (b¹Σ⁺); 而激发态的CN是通过N(⁴S) + CBr→CN(A, B) + Br过程形成的.     

白石湖煤THF萃取物中硫、氮化合物赋存形态

采用四氢呋喃(THF)对白石湖煤进行索氏萃取,萃取液在四氟硼酸银存在下与碘甲烷反应,转化成甲基磺酸盐。采用电喷雾电离(ESI)傅里叶变换离子回旋共振质谱(FT-ICR MS)对甲基硫盐和含氮化合物进行了表征,结合硫、氮化学发光检测器(GC-SCD和GC-NCD)分析,研究THF萃取物中硫、氮化合物形态。结果表明,THF萃取物中主要是S_1、S_2、N_1、N_1O_1类化合物,含量较高的硫、氮化合物分别是二苯并噻吩类化合物及咔唑类化合物。     

Energy distributions of CO produced in an acetone-containing discharge

Tunable infrared diode laser absorption (TDLAS) and Fourier transform infrared absorption spectroscopies (FTIR) have been utilized to characterize the translational, rotational and vibrational distributions of CO in an acetone/argon DC plasma at total pressures ranging from 4 to 5 Torr and currents of 0.1–0.3 A. A broad vibrational distribution of CO was observed with gradually decreasing intensities from the fundamental band to v=12←11. When nitrogen was added to the plasma, the distribution is narrower, due to the efficient energy transfer between CO and N₂ molecules. The measured translational temperature in such plasmas ranged from 400–550 K. The rotational distribution can generally be fitted to a Boltzmann distribution within each vibrational level although the rotational temperature is highest for the lowest vibrational quantum number.