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1.
Absorption and fluorescent scattering of nitrogen laser radiation by a low-pressure RF laboratory plasma ( ne = 10 12 cm −3) has been observed for the first negative system of N 2+. A 67±1 ns lifetime of N 2+ (B 2Σ u+) was experimentally measured from the laser-induced fluorescence. In addition, enough collisionally excited N 2 (B 3Π g) was produced to observe laser-induced fluorescence for the second positive system of N 2. The lifetime of N 2 (C 3Π u) was found to be 41±2 ns. The measured lifetimes are in good agreement with published values calculated from theory. 相似文献
2.
A mixture of NF 3 and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF 2. When H 2, D 2, or CH 4 are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH 3. The latter free radicals can react with NF 2, probably by an elimination reaction to produce electronically excited NF: NF 2( 2B 1) + H(D, CH 3) → HF *(DF * + NF(a 1Δ). 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(a 1Δ) → HF(ν−2) + NF(b 1Σ +). A similar transfer process has also been found between the electronically excited a 1Δ states of O 2 and NF: O 2(a 1Δ) + NF(a 1Δ) → O 2(X 3Σ −) + NF(b 1Σ +). The H or D atoms but not the CH 3 radicals are then found to react with either NF(a 1Δ) or NF(X 3Σ −) to produce electronically excited N( 2D) atoms, which in turn react with the NF(a 1Δ) molecules to produce N 2(B 3Π 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) + N 2O → NO(B 2Π r) + N 2 (X 1Σ +g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A 3Π), which has not been previously reported. 相似文献
3.
The electric field gradients (EFG’s) at the nucleus are calculated as a function of internuclear separation in the X 2Σ g+ and B 2Σ 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 N 2+ results are supported by analogous calculations on the X 1Σ g+ and A 3Σ u+ states of N 2, 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 N 2+ and N 2. 相似文献
4.
The A 2Π u-X 2Π g electronic emission spectrum of I 2+ has been recorded at a low rotational temperature in a crossed molecular beam/electron beam apparatus. Six vibrational sequences with five or more members have been assigned to progressions in ν′, giving ω′ e = 122±8 cm −1, but a full vibrational analysis has not been possible. It is not known whether this is due to the relatively poor resolution (≈5 cm −1) at which the spectrum has been recorded or because the A 2Π u state is perturbed in one or both spin-orbit components. Existing data on the A state of I 2+ are reviewed. 相似文献
5.
The recombination of nitrogen atoms on polycrystalline samples of cobalt and nickel produces metastable electronically excited nitrogen molecules, probably N 2(W 3Δ u), which are collisionally transferred to the N 2(B 3Πg) state. Information about vibrational relaxation of the metastable state by N 2(X 1Σ +g) is inferred from composition dependent changes in the observed first positive emission spectrum [N 29A 3Σ +g)−N 2(B 3Π g] with the aid of multilevel, steady-state, kinetic model. 相似文献
6.
The results of theoretical studies on structures and energetics are presented for proton-bound complexes N 2H +–XH, N 2H +–X 2, and N 2H +–XY(YX) (X=Y=F, Cl, and Br). In all the monocations complexes, the halogen atom shares a proton with N 2. The calculated energetic results show that the stability decreases when descending in the corresponding periodic table column. The possible proton transfer dissociation processes of N 2H ++XH, N 2H ++X 2, and N 2H ++XY systems into XH 2+, X 2H +, XYH +, and YXH + and molecular N 2 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. 相似文献
7.
Medium-resolution spectra of the N 2 b 1Π u-X 1Σ g+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Π u state: Δν 0 = 0.50 ± 0.05 cm −1, Δν 1 = 0.28 ± 0.02 cm −1, Δν 2 = 0.65 ± 0.06 cm −1, Δν 3 = 3.2 ± 0.5 cm −1, Δν 4 = 0.60 ± 0.07 cm −1, and Δν 5 = 0.28 ± 0.02 cm −1. From these linewidths, predissociation lifetimes τ ν were obtained: τ 0 = 16 ± 3 ps, τ 1 > 150 ps, τ 2 = 10 ± 2 ps, τ 3 = 1.6 ± 0.3 ps, τ 4 = 9 ± 2 ps, and τ 5 > 150 ps. Band origins and rotational constants for the b 1Π uν = 0 and 1 levels were determined for the 14N 2 and 14N 15N molecules. 相似文献
8.
Rotational-state distributions of the CO + (A–X, B–X) and N 2+(B–X) emissions produced by the collisions of He(2 3S) with CO and N 2 were studied in the collision energy ( ER range 100–200 meV. The rotational populations of the emitting states can be fitte by single Boltzmann temperatures ( TR. The TR (320 ± 30 K) for the ν′ = 3 and 4 levels of the CO + (A 2Π) state are nearly independent of, or slightly increase with, ER, while TR for the CO +(B 2Σ +, ν′ = 0) state increases rapidly with ER.The TR (430 ± 20 K) for the N 2+(B 2Σ +, ν′ = 0) state is nearly independent or slightly decreases with increasing ER. Interactions providing these trends are discussed. 相似文献
9.
The fraction FΣ of excited-state oxygen formed as b 1Σ g+ was determined for a series of triplet-state photosensitizers in CCl 4 solutions. FΣ was determined by monitoring the intensities of (a) O 2(b 1Σ g+) fluorescence at 1926 nm (O 2(b 1Σ g+)→O 2(a 1Δ g) and (b) O 2(a 1 Δ g) phosphorescence at 1270 nm (O 2(a 1Δ g) → O 2(X 3Σ g−)). Oxygen excited states were formed by energy transfer from substituted benzophenones and acetophenones. The data indicate that FΣ depends on several variables including the orbital configuration of the lowest triplet state and the triplet-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely to influence FΣ strongly by CT-mediated mixing of various sensitizer-oxygen states. 相似文献
10.
Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH 3CHSH + (1 +), trans-CH 3CHSH + (2 +), and CH 3SCH 2+ (3 +): 1 +→CH 3++ trans-HCSH (1); 1 +→CH 3+ trans-HCSH + (2); 1 +→CH 4+HCS + (3); 1 +→H 2+ c-CH 2CHS + (4); 2 +→H 2+CH 3CS + (5); and 3 +→H 2+ c-CH 2CHS + (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol −1, respectively. Loss of CH 4 from 1 + (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol −1 and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol −1 and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H 2. Formation of CH 3CS + from 2 + (reaction (5)) by loss of H 2 proceeds through protonation of the methine (C H) group, followed by dissociation of the H 2 moiety. Its energy barrier is 276 kJ mol −1. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H 2 1,1-elimination from 3 + (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH 3SCH 2+ and has a critical energy of 269 kJ mol −1. 相似文献
11.
The radiative lifetimes of nine vibrational levels of the C 3( 1Π u) radical were obtained from decay time studies of the C 3( 1Π u → 1Σ +g) fluorescence induced by a tunable dye laser. The lifetimes of the different vibronic levels were found to be constant within the experimental error limits, namely, τ o = (200 ± 10) ns. The collisional deactivation of the C 3( 1Π u) states by helium gives rate constants between 2.5 and 4 in 10 −11 cm 3 molecule −1 s −1 units. 相似文献
12.
Two-centre model potential calculations have been carried out for the 2Σ +g,u and 2Π g,u states of Li +2, Na +2, K +2, Rb +2 and Cs +2. Comparison with other model potential calculations suggests that reliable potential curves have been obtained. The results indicate the usefulness of calculating diatomic energies by the method proposed. 相似文献
13.
The mechanism of the H 2NO( 2B 1)→NO( 2Π)+H 2 reaction has been examined using ab initio molecular orbital methods. Ground-state and first-excited-state potential surfaces were plotted at the FOCI/cc-pVTZ level of theory as functions of two appropriate internal degrees of freedom. A conical intersection was found on the Cs pathway that is symmetric with respect to the plane perpendicular to the molecular plane of C2v H 2NO( 2B 1). It is therefore considered that trajectories that start from H 2NO( 2B 1) towards the product region detour around the conical intersection, pass through the neighborhood of the transition state that is located at the saddle point on the Cs pathway, and finally reach the products, NO( 2Π)+H 2. Thus we can explain the mechanism of the H 2NO( 2B 1)→NO( 2Π)+H 2 reaction, which has remained unclear to date. 相似文献
14.
A theoretical study of the NaC 3+ and NaC 3H + systems has been carried out. Predictions have been made for some of the molecular properties, which could help in their possible experimental detection. The predicted global minimum for NaC 3+ is the linear isomer 1s ( 1Σ). The lowest-lying triplet state is a three-membered ring 3t ( 3B 2), lying about 27.1 kcal/mol higher in energy than the predicted global minimum at the G2(P) level. In the case of NaC 3H +, there are two isomers that lie close in energy: a linear species, 1d ( 2Π), and a three-membered ring, 4d ( 2A′). The most reliable levels of theory employed predict that 1d ( 2Π) is the global minimum, whereas 4d ( 2A′) is predicted to lie 5.3 kcal/mol higher in energy at the G2(P) level. In any case it seems that both structures could be accessible to experimental detection. Low ionization potential and high proton affinities are obtained for the most stable NaC 3 isomers. Therefore, if present in the interstellar medium, NaC 3 should be easily ionized and would react quite easily to give the protonated species. 相似文献
15.
The Ca( 1D 2, 3P J) + CH 3 → CaI(A,B) + CH 3 reactions system has been studied by measuring its chemiluminescence under beam-gas conditions. Absolute values of the state-to-state reaction cross-sections were determined at low collision energy
. In addition, the electronic branching ratio and product energy disposal have been determined for each metastable reaction. The major changed observed in the chemiluminescence when comparing the Ca( 1D 2) reaction versus that of Ca( 3P J) is the total yield associated with the former reaction. To the best of our spectral resolution neither the electronic branching ratio e.g. CaI(A)/CaI(B) nor the internal CaI energy disposal change significantly as the metastable Ca( 1D 2)/Ca( 3P J) ratio is varied. In spite of the fact that the Ca( 3P J) reaction is less exoergic, the CaI product appears with a higher fraction of internal energy than that of Ca( 1D 2) reaction. Thus, the fraction of the total energy appearing in CaI internal energy amounts to 57.5% in the Ca( 3P J) reaction while it is 19.3% only for the Ca( 1D 2) reaction. This difference is discussed in the light of a distinct mechanism associated with the attack of the excited Ca atom into the C---I bond. No significant chemiluminescence yield was found for the energetically open CaCH *3 channels. The product chemiluminescence polarization was also measured as a function of the metastable concentration. A significant degree of polarization was found depending upon the specific electronic excitation. The analysis of the polarization emission associated to the parallel CaI(X 2Σ+ ← B 2Σ+) emission led into a strong polarization of the product rotational angular momentum. The comparison of the product rotational alignment for the kinematically identical Ca(1D2, 3PJ, 1P1) + CH3 → CaI* (B2Σ+) + CH3 reaction system showed that the CaI rotational polarization diminishes in the 3PJ → 1D2 → 1P1 sequence, e.g. as the reaction exothermicity increases. In addition the degree of polarization associated with other emission bands as for example CaI(X 2Σ+ ← A 2Π1/2) indicates the presence of a parallel transition which was been interpreted as mixing of Hund's case (a) and (c) appropriate for this heavy CaI diatom produced with a high rotational excitation. 相似文献
16.
Single and multiple photon processes are identified in the 193 nm excimer laser photolysis of CS 2. CS(X 1Σ +, υ = 1 to 5, J = 5 to 45) is observed by dye laser induced fluorescence of the A 1Π ↔ ; X 1Σ + transition, following the single photon 193 nm photolysis of CS 2. Multiple photon 193 nm generation of CS fragment emission from 620 to 170 nm is also reported. A partial assignment of the emission spectrum identifies fluorescence from the CS A′ 1Σ + and A 1Π states. 相似文献
17.
A laser pulse-and-probe method has been used to determine the nascent vibrational populations in NO( v=0–4) and O 2( v=6–11) formed in the thermal reaction: O( 3P) + NO 2 → O 2( v) + NO( v). A frequency-tripled Nd: YAG laser is used to photolyse NO 2, diluted tenfold in Ar, and laser-induced fluorescence spectroscopy in the NO A 2Σ +-X 2Π and O 2 B 3Σ −u -X 3Σ −g electronic band system is used both to follow the kinetics of individual vibrational states and to determine the nascent vibrational distributions. The majority of the NO product is formed in v = 0 and the average vibrational yield is ≈ 4.6%. The O 2 populations fall monotonically from v = 6 to 11 in a distribution close to what is expected on prior grounds. Based on a surprisal analysis, the average vibrational energy yield in O 2 is ≈ 26%. The nature of the reaction dynamics is discussed. 相似文献
18.
采用溶胶-凝胶法制备了不同含量钨修饰的MnO x-Fe 2O 3催化剂,重点考察WO 3的引入对NH 3-SCR反应中N 2选择性的影响,通过XRD、BET、XPS、H 2-TPR、Raman和In situ DRIFTS等手段对催化剂的物理化学性质进行表征。结果表明,钨的引入显著提高NH 3-SCR的N 2选择性,当WO 3质量分数为15%时,具有最佳的NH 3-SCR催化性能,且在50-250℃条件下N 2O浓度始终低于0.003%。这主要是由于适量WO 3的引入,导致催化剂物相由α-Fe 2O 3向γ-Fe 2O 3转变,并与锰相互作用形成新的无定型MnWO 4,获得较大的比表面积;使得Mn 4+/(Mn 3++Mn 4+)比例减少但Fe 2+及表面化学吸附氧(O α)含量增加,从而降低催化剂氧化性;增强催化剂表面的Lewis酸性位点的含量及强度,增强NH 3的吸附,促进了SCR反应,同时抑制了NO 2深度氧化形成硝酸盐物种,降低硝酸盐物种还原产生的副产物N 2O含量,从而显著提高WO 3-MnO x-Fe 2O 3催化剂在NH 3-SCR中的N 2选择性。 相似文献
19.
Thionitrosyl hexafluoroarsenate, [NS][AsF 6], reacted with caesium azide, [Cs][N 3], to form S 2N 2 which polymerized to give (SN) x. The structures of the following likely intermediate species were calculated at correlated MP2/6–31G(d,p) level of theory (relative energies in kcal mol −1): thionitrosyl azide, N 3---N=S (37.8), thiazyl azide, N 3---SN (39.2) and cyclic N 4S (0.0). ‡ 相似文献
20.
The paper reports results of a study on the specific adsorption of F −, Cl −, Br −, I −, ClO 3−, BrO 3−, IO 3− and IO 4− on hydrous γ-Al 2O 3. The isotherms of the anion adsorption and the adsorption dependencies on pH and the ionic strength of the solution have been determined under the equilibrium conditions. According to the degree of affinity to γ-Al 2O 3, the anions can be ordered as: I −3− −−3−3−4−−. It has been established that the sorption of IO4− and F− involves the formation of surface complexes in the inner co-ordination sphere, whereas that of Cl−, Br−, I−, ClO3−, BrO3− and IO3− takes place through formation of ion pair complexes in the outer co-ordination sphere. In the dynamic system, the exchange isoplanes and elution curves have been determined for selected anions on columns filled with Al2O3. It has been shown that γ-Al2O3 can be used for isolation and concentration of IO3− from natural waters in order to decrease the limit of the ions determination to 2 μg l−1. Using differential pulse voltammetry (DPV), after isolation and concentration on γ-Al2O3, the content of iodates has been determined in mineral, marine and tap water doped with these ions. 相似文献
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