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1.
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
2.
The CS(A 1Π → X 1Σ +) emission spectra resulting from the energy transfer reaction of Ar( 3P 2) + CS 2 under single collision condition have been obtained. The relative vibrational populations of the nascent product CS(A 1Π, υ′) have been determined by means of spectral simulation. A population inversion is found at υ′ = 1. The population data are approximately represented by a distribution predicted from the impulsive half collision model. The dynamics and energetics of CS(A) formation has been discussed in detail. 相似文献
3.
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
4.
Saddle point geometries and barrier heights have been calculated for the H abstraction reaction HO 2( 2A″)+H( 2S) → H 2( 1Σ +g)+O 2( 3Σ −g) and the concerted H approach-O removing reaction HO 2 ( 2A″)+H( 2S) → H 2O( 1A 1)+O( 3P) by using SDCI wavefunctions with a valence double-zeta plus polarization basis set. The saddle points are found to be of C s symmetry and the barrier heights are respectively 5.3 and 19.8 kcal by including size consistent correction. Moreoever kinetic parameters have been evaluated within the framework of the TST theory. So activation energies and the rate constants are estimated to be respectively 2.3 kcal and 0.4×10 9 ℓ mol −1 s −1 for the first reaction, 20.0 kcal and 5.4.10 −5 ℓ mol −1 s −1 for the second. Comparison of these results with experimental determinations shows that hydrogen abstraction on HO 2 is an efficient mechanism for the formation of H 2 + O 2, while the concerted mechanism envisaged for the formation of H 2O + O is highly unlikely. 相似文献
5.
Classical trajectory calculation has been performed for the H+H→H 2/Si(100)-(2×1) reaction by the 3D Generalized Langevin Equation (GLE) approach. The implementation of the 3D GLE approach to the H+H→H 2/Si(100)-(2×1) reaction is presented. Reaction probabilities are calculated for given surface temperatures and given collision energies. We also calculated vibrational and rotational distributions of product H 2 molecules from the reaction. About 80% of the product hydrogen molecules are in the ground vibrational state and the remaining 20% of the products are in the excited states. The rotational state shows non-Boltzmann distribution which can be seen in the direct collision process. Vibrational and Rotational distributions are strongly related to the impact parameter. The vibrational distribution is correlated with the x-component of the impact parameter and reflects the dimer nature of the silicon (2×1) surface. Details of the dynamics involving vibrational and rotational transitions are discussed. 相似文献
6.
Absolute kinetic energy distributions and yields associated with ground state 3P and excited state 1D oxygen atoms have been obtained for O − anion electron stimulated desorption from condensed O 2 in the electron energy range 6–15 eV. The observed yields are understood as resulting essentially from dissociative electron attachment reactions via the two lowest 2Σ +g O −2 resonance states through adiabatic and non-adiabatic transitions to the limits O −( 2P) + O( 3P) and O −( 2P) + O( 1D). The kinetic energy distributions show the prominent role of electron multiple collision processes and post-dissociation interactions of the O − anions in the condensed phase. 相似文献
7.
The 3 ν 1 + ν 3 vibrational overtone spectrum of 13CH 4 is recorded under Doppler-limited resolution conditions using a titanium sapphire laser-based photoacoustic spectrometer. Data at two temperatures, 100 and 293 K, are presented. The observed spectral congestion is qualitatively similar to that observed for 12CH 4, but the detailed ro-vibrational structure of the two isotope variants is completely different. The data reflect the complicating influences of tetrahedral fine structure and vibrational state mixing. 相似文献
8.
The reactions of the half-sandwich molybdenum(III) complexes CpMo(η 4-C 4H 4R 2)(CH 3) 2, where Cp=η 5-C 5H 5 and R=H or CH 3, with equimolar amounts of B(C 6F 5) 3 have been investigated in toluene. EPR monitoring shows the formation of an addition product which does not readily react with Lewis bases such as ethylene, pyridine, or PMe 3. The analysis of the EPR properties and the X-ray structure of a decomposition product obtained from dichloromethane, [CpMo(η 4-C 4H 6)(μ-Cl)(μ-CH 2)(O)MoCp][CH 3B(C 6F 5) 3], indicate that the borane attack has occurred at the methyl position. 相似文献
9.
The product isolated from the reaction of (μ-H) 2Os 3(CO) 9(PPh 3) with ethylene is shown to be the ethylidene complex (μ-H) 2Os 3(CO) 9(PPh 3)(μ-CHCH 3) (1) rather than the ethylene complex (μ-H)(H)Os 3(CO) 9(PPh 3)(C 2H 4), as previously claimed. The characterization of 1 is based on a combination of 1H and 13C NMR results. The 1H NMR data (δ 6.84 (1 H D), 2.53 (3 H C), J(CD) = 7.4 Hz) establish the presence of the ethylidene moiety, whereas detailed analysis of the 1-D and 2-D 13C NMR spectra of 13CO-enriched 1 indicates the relative positions of the ethylidene, hydride, and phosphine ligands on the triosmium framework. 相似文献
10.
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
11.
The mechanism of the transformation of (η 5-C 5H 5) 2NbCl 2 to (η 5-C 5H 5) 2NbH 3 by hydridoaluminate reducing agents has been investigated. Results suggest disproportionation of a niobium(IV) hydrite, leading to the trihydride product and a niobium(III) hydridoaluminate, (η 5-C 5H 5) 2NbH 2AlR 2, which in turn is converted to the trihydride on hydrolysis. (η 5-C 5H 5) 2NbH 2AlH 2 has been isolated; deuterium labelling shows that hydrogens exchange between ring and metal-bridging positions in this molecule. 相似文献
12.
The reactions of the diruthenium carbonyl complexes [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)]X (X=BF 4− (1a) or PF 6− (1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-(L,L)) 2]X n ((L,L)=acetate (O 2CMe), 2,2′-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)] + either migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)] + (1) with 2,2′-bipyridine produces [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe) 2] (2), [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe)(η 2-bpy)] + (3), and [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-bpy) 2] 2+ (4). Alternatively compound 2 can be prepared from the reaction of 1a with MeCO 2H–Et 3N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone–Et 3N produces [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe)(η 2-acac)] (5) and [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-acac) 2] (6). Compound 2 can also react with acetylacetone–Et 3N to produce 6. Surprisingly [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-quin) 2] (7) was obtained stereospecifically as the only one product from the reaction of 1b with 8-quinolinol–Et 3N. The structure of 7 has been established by X-ray crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere π–π face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV–vis spectrum. 相似文献
13.
The complex [MoW(μ-CC 6H 4Me-4)(CO) 2(η 7-C 7H 7)(η 5-C 2B 9H 10Me)] reacts with diazomethane in Et 2O containing EtOH to afford the dimetal compound [MoW(OEt)(μ-CH 2){μ-C(C 6H 4Me-4)C(Me)O}(η 7-C 7H 7)(η 5-C 2B 9H 10Me)]. The structure of this product was established by X-ray diffraction. The Mo---W bond [2.778(4) Å] is bridged by a CH 2 group [μ-C---Mo 2.14(3), μ-C---W 2.02(3) Å] and by a C(C 6H 4Me-4)C(Me)O fragment [Mo---O 2.11(3), W---O 2.18(2), Mo---C(C 6H 4Me-4) 2.41(3), W---C(C 6H 4Me-4) 2.09(3), Mo---C(Me) 2.26(3) Å]. The molybdenum atom is η 7-coordinated by the C 7H 7 ring and the tungsten atom is η 5-coordinated by the open pentagonal face of the nido-icosahedral C 2B 9H 10Me cage. The tungsten atom also carries a terminally bound OEt group [W---O 1.88(3) Å]. The 1H and 13C-{ 1H} NMR data for the dimetal compound are reported and discussed. 相似文献
14.
The XeOSeF 5+ cation has been synthesized for the first time and characterized in solution by 19F, 77Se and 129Xe NMR spectroscopy and in the solid state by X-ray crystallography and Raman spectroscopy with AsF 6− as its counter anion. The X-ray crystal structures of the tellurium analogue and of the Xe(OChF 5) 2 derivatives have also been determined: [XeOChF 5][AsF 6] crystallize in tetragonal systems, P4/ n, a=6.1356(1) Å, c=13.8232(2) Å, V=520.383(14) Å 3, Z=2 and R1=0.0453 at −60°C (Te) and a=6.1195(7) Å, c=13.0315(2) Å, V=488.01(8) Å 3, Z=2 and R1=0.0730 at −113°C (Se); Xe(OTeF 5) 2 crystallizes in a monoclinic system, P2 1/ c, a=10.289(2) Å, b=9.605(2) Å, c=10.478(2) Å, β=106.599(4)°, V=992.3(3) Å 3, Z=4 and R1=0.0680 at −127°C; Xe(OSeF 5) 2 crystallizes in a triclinic system,
, a=8.3859(6) Å, c=12.0355(13) Å, V=732.98(11) Å 3, Z=3 and R1=0.0504 at −45°C. The energy minimized geometries and vibrational frequencies of the XeOChF 5+ cations and Xe(OChF 5) 2 were calculated using density functional theory, allowing for definitive assignments of their experimental vibrational spectra. 相似文献
15.
The quasiclassical trajectory calculation of the I + HI collision is performed in order to study the exchange and endothermic reaction channels. The rate constant of the exchange reaction I′ + HI → HI′ + I is found to be equal to 7.7 × 10 11 cm 3/mol s at room temperature of 300 K. The study of the endothermic reaction I + HI → H + I 2 shows that it takes place only in configurations with large bend angles. Due to the non-collinear character of this reaction its threshold (2 eV) exceeds significantly the threshold of the minimal energy (collinear) reaction path (1.55 eV). 相似文献
16.
On the basis of ab initio MP2/6–31 + + G(2d,2p) calculations, we examined the potential energy surfaces of the water·hydrocarbon complexes H 2O·CH 4, H 2O·C 2H 2 and H 2O·C 2H 2 to locate all the minimum energy structures and estimate the hydrogen bond energies and vibrational frequencies associated with the C(sp n)---H·O and the O---H·C(sp n) bonds ( n = 1−3). Our calculations show that H 2O·C 2H 2, H 2O·C 2H 4 and H 2O·CH 4 have two minimum energy structures (i.e., the C---H·O and O---H·C hydrogen bond forms), but H 2O·C 2H 4 has only one when the vibrational motion is taken into account, the O---H·C hydrogen bond form. We have also computed the barrier for the interconversion from one minimum to the other. The fully optimized geometries of H 2O·CH 4, H 2O·C 2H 4 and H 2O·C 2H 2 as well as the vibrational shifts of the C---H stretching frequencies in their C---H·O hydrogen-bonded forms are in good agreement with the available experimental data. The calculated hydrogen bond energies show that the C(sp n---H·O bond strengths decrease in the order C(sp)---H·O>C(sp 2)---H·O>C(sp 3)---O>C(sp 3---H·O, which is also consistent with the available experimental data. 相似文献
17.
Autoionizing Rydberg levels of Li 2 molecules in a supersonic molecular beam are populated by stepwise excitation with two tunable pulsed dye lasers. The observed autoionization spectra show severe perturbations. Based on calculations of quantum defects and a perturbation treatment of l-uncoupling a tentative assignment of Rydberg series up to n = 32 is proposed. The convergence limits of these series yield a value of IP = 41475 cm −1 for the adiabatic ionization potential and a vibrational constant ω e = 263 cm −1 for the X 2Σ +g ground state of Li +2. The experimental results are compared with ab initio calculations combined with a core polarization potential, which yield the potential curve. the dissociation energy, the quadrupole moment and the vibrational frequency for the X 2Σ +g ground state of Li +2, in the excellent agreement with experimental findings. 相似文献
18.
The 60-electron tetrahedral clusters W 2Ir 2(μ-L)(CO) 8(η 5-C 5H 4Me) 2 [L=dppe (2), dppf (3)] have been prepared from reaction between W 2Ir 2(CO) 10(η 5-C 5H 4Me) 2 (1) and the corresponding diphosphine in 52 and 66% yields, respectively. A structural study of 2 reveals that three edges of a WIr 2 face are spanned by bridging carbonyls, that the iridium-ligated diphosphine coordinates diaxially and that the tungsten-bound methylcyclopentadienyls coordinate axially and apically with respect to the plane of bridging carbonyls. A structural study of 3 reveals that the dppf ligand bridges an Ir---Ir bond which is also spanned by a bridging carbonyl; tungsten-ligated methylcyclopentadienyl ligands and terminal carbonyls result in electronic asymmetry (17e and 19e iridium atoms) in the electron-precise cluster. Both clusters show two reversible one-electron oxidation processes and an irreversible two-electron reduction; the dppf-containing cluster 3 has a further, irreversible, one-electron oxidation process. UV–vis-NIR spectroelectrochemical studies of the 2→2 +→2 2+ progression reveal the appearance of a low-energy transition on oxidation to 2 + which persists on further oxidation to 2 2+. 相似文献
19.
The bimetallic [Pt(NH 3) 4] 2[W(CN) 8][NO 3]·2H 2O is characterised by single-crystal X-ray diffraction [S.G. P2 1/ m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1) * separations of 4.77(2), 4.55(2) * and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO 3− between parallel [Pt(1)(NH 3) 4] 2+ planes and the second consists of [W(CN) 8] 3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH 3) 4] 2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH 3 ligands, water molecules and oxygen atoms of NO 3− counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer. 相似文献
20.
A high yield synthesis of the carbonyl dithiocarbamato derivative Fe(CO) 2(η 2-S 2CNMe 2) 2 and Fe(η 2-S 2CNMe 2) 2 by photolysis with visible light of solutions containing Fe 2(CO) 9 or Fe 3(CO) 12 and [(η 5-C 5H 5)(CO) 3W(η 1-SCSNMe 2)] is reported. 相似文献
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