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1.
Kinetic energy releases from the unimolecular H 2 (D 2) elimination reactions of energy-selected à 2B 3gC 2H 4+(C 2D 4+) have been obtained by a photoelectron-photoion coincidence technique. The energy releases suggest a 1,1 elimination and are compatible with the presence of a small reverse activation energy barrier of the order of 0.02 eV. Such a barrier was indicated by a detailed ab initio study of this dissociation and the present results are discussed in the light of this theoretical treatment. 相似文献
2.
The reactions of methane with the dications C 7H 62+, C 7H 72+, and C 7H 82+ generated by electron ionization of toluene are studied using mass-spectrometry tools. It is shown that the reactivity is dominated by the formation of doubly charged intermediates, which can either eliminate molecular hydrogen to yield doubly charged products or undergo charge-separation reactions leading to the formation of a methyl cation and the corresponding C 7H n+1+ monocation. Typical processes observed for dications, like electron transfer or proton transfer, are largely suppressed. The theoretically derived mechanism of the reaction between C 7H 62+ and CH 4 indicates that the formation of the doubly charged intermediate is kinetically preferred at low internal energies of the reactants. In agreement, the experimental results show a pronounced hydrogen scrambling and dominant formation of the doubly charged products at low collision energies, whereas direct hydride transfer prevails at larger collision energies. 相似文献
3.
Photoion-photoion coincidence spectra of benzene and benzene- d6 photoionized by He(II) light and synchrotron radiation show the existence of six major and eight minor charge-separation reactions of the [C 6H 6] 2+ ion. Three main groups of ion pairs are related to [C 3H 3] + + [C 3H 3] +, [C 2H 3] + + [C 4H 3] + and [CH 3] + + [C 5H 3] +, with appearance energies of 32.2 ± 0.5 eV, 31.3 ± 0.5 eV and 28.4 ± 0.3 eV. The kinetic energy release is the same for all pairs within a group, irrespective of hydrogen number, but differs from group to group. Results are interpreted in terms of fast, direct charge separation of [C 6H 6] 2+, and subsequent hydrogen loss by the singly charged fragments. 相似文献
4.
The reaction of Ar + with H 2O has been investigated at near-thermal energy. The product ions H 2O + and ArH + account for 90 and 10% of the total reaction rate, respectively. Kinetic energy measurements and emission spectroscopy of the H 2O + product ions are reported. It is concluded that at least 60% of H 2O + ions are in the X? state with ≈2.4 eV vibrational energy while up to 40% are in the à state with a mean vibrational energy of 1.4 eV; the à state vibrational distribution has been determined. It is shown that both H 2O + states are populated via an energetically “non-resonant” charge transfer process. 相似文献
6.
The collision-induced breakup of CH 3O 2+ ions, produced in various binary ion—neutral reactions, was investigated in a drift experiment in the energy range from 0.2 to 1.2 eV. The products observed were HCO + (50%) and H 3O + (50%), independent of the collision energy inducing the breakup. The energy barrier for the breakup is 22 ± 6 kcal/mole. 相似文献
7.
The reaction of N 2O with CO, catalyzed by Fe +(C 6H 6) and producing N 2 and CO 2, has been investigated at the UB3LYP/6-311+G(d) level. The computation results revealed that the reaction of Fe +(C 6H 6), N 2O and CO, is an O-atom abstraction mechanism. For the reaction channels, the geometries and the vibrational frequencies of all species have been calculated and the frequency modes analysis also have been given to elucidate the reaction mechanism. On the basis for geometry optimizations, the thermodynamic data of these reactions channels have been calculated using the statistical theory at 295.15 K and pressure of 0.35 Torr. Using Eyring transition state theory with Wigner correction, the activation thermodynamic data, rate constant and frequency factors for the these reaction channels also have been given. The results showed that CO and N 2O do not react without catalyst and Fe +(C 6H 6) can excellently mediate the reaction of N 2O and CO. 相似文献
8.
In this communication are presented exact quantum mechanical nonadiabatic electronic transition probabilities for the collinear reaction Ar + + H 2( vi = 0) → ArH +( vf) + H. The calculations were performed using a potential surface calculated by the DIM method. It is established that large probabilities (≈ 1.0) can be obtained only if there is enough translational energy to overcome a potential barrier formed due to the crossing between vi = 0 of the Ar + + H 2 system and vi = 2 of the Ar + H +2 system. The threshold for the reaction is found to be 0.06 eV. 相似文献
9.
Reaction and charge transfer of H +2 + Ar to give ArH + and Ar + have been investigated as a function of H +2 vibrational quantum state and kinetic energy ( Ec.m.), using photoionization and guided beam ion optics. Resonance effects are important in charge transfer; proton and charge transfer are closely coupled for Ec.m. 3 eV. 相似文献
10.
The rate constants and modes of reaction of NO 2+ and C 2H 5ONO 2NO 2+ with aromatic compounds and alkanes have been determined in a pulsed ion cyclotron resonance mass spectrometer. Both ions undergo competing charge transfer and substitution reactions (NO 2+ + M → MO + + NO; C 2H 5ONO 2NO 2+ + M → MNO 2+ + C 2H 5ONO 2) with aromatic molecules. In both cases, the probability that a collision results in charge transfer increases with increasing exothermicity of that process. The C 2H 5ONO 2NO 2+ ion does not undergo charge transfer with molecules having an ionization potential greater than about 212 kcal/mol (9.2 eV); this observation leads to an estimate of 13 kcal/mol for the binding energy between NO 2+ and C 2H 5ONO 2. The importance of the substitution reaction depends on the number of substituents on the aromatic ring and the molecular structure, and, in the case of C 2H 5ONO 2NO 2+ ions, on the energetics of the competing charge transfer process. Both NO 2+ and C 2H 5ONO 2NO 2+ undergo hydride transfer reactions with alkanes. For both these ions, k(hydride transfer)/ k (collision) increases with increasing exothermicity of reaction, but in both cases the rate constants of reaction are unusually low when compared with other hydride transfer reactions of comparable exothermicity which have been reported in the literature. This is interpreted as evidence that the attack on the alkane preferentially involves the nitrogen atom (where the charge is localized) rather than one of the oxygen atoms of NO 2+. 相似文献
11.
The photoionization and dissociative photoionization of m-xylene (C8H10) were researched by using synchrotron radiation vacuum ultraviolet (SR-VUV) and supersonic expanding molecular beam reflectron time-of-flight mass spectrometer (RFTOF-MS) system. The photoionization efficiency spectra (PIEs) of parent ion C8H10+ and main fragment ions C8H9+ and C7H7+ were observed, and the ionization energy (IE) of m-xylene and appearance energies (AEs) of main fragment ions C8H9+ and C7H7+ were determined to be 8.60 ± 0.03 eV, 11.76 ± 0.04 eV and 11.85 ± 0.05 eV, respectively. Structures of reactant, transition states (TSs), intermediates (INTs), and products involved in two dominant dissociation channels were optimized at the B3LYP/6-311++G(d,p) level, and the relative energies were calculated at the G3 level. Based on the results, two major dissociative photoionization channels, C7H7++CH3 and C8H9++H were calculated at the B3LYP/6-311++G(d,p) level. On the basis of theoretical and experimental results, the dissociative photoionization mechanisms of m-xylene were proposed. The C–H or C–C bond dissociation and hydrogen migration are the main processes in the dissociation channels of m-xylene cation. 相似文献
12.
Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH 3+(CH 4, H 2)C 2H 5+ are analysed. It is shown that the evidence for the former can equally well be interpreted in terms of a proposed model of persistent complex formation and decay. The plausibility of a “direct” mechanism is discussed and is found to be poor. 相似文献
13.
The 0.1 eV translational energy reactions of CH +3 and CD +3 with acetonitrile were studied in a tandem Dempster-ion cyclotron resonance mass spectrometer. Channels leading to CH 3CNH + (7%), H 2CN + (58%), and C 2H +5 (35%) were observed. For CD +3 reactant ions the H 2CN + and C 2H +5 products show evidence of complete H, D isotopic scrambling, suggesting an intermediate complex. 相似文献
14.
C 2(a 3π u) disappearance rate constants of 1.44, 0.96, 0.0296, 0.0130 and < 10 ?6(x10 ?10cm 3s ?1) are reported for reactions with C 2H 4, C 2H 2, O 2, C 2H 6, and CH 4, respectively at 298 K. C 2(a 3π u) fragments are generated by multiphoton ArF excimer laser photodissociation at C 2H 2, and monitored by dye laser induced fluorescence. Arguments are presented which favor chemical reactions over the C 2(a 3π u) → (X 1σ +g) quenching channel. C 2 + C 2H 2 represents the one possible exception to the reactive channel. 相似文献
15.
The reactions of Fe(CO) 5, Fe(CO) 4P(C 6H 5) 3, M(CO) 6 (M W, Mo, Cr), and (CH 3C 5H 4Mn(CO) 3 with KH and several boron and aluminium hydrides were investigated. Iron pentacarbonyl was converted quantitatively to K +Fe(CO) 4-(CHO) by hydride transfer from KBH(OCH 3) 3 allowing isolation of [P(C 6H 5) 3] 2-N n+Fe(CO) 4(CHO) ? in 50% yield. Lower yields were obtained with LiBH(C 2H 5) 3, and other hydride sources gave little or no formyl product. The stability of Fe(CO) 4(CHO) ? in THP was found to depend on the cation, decreasing in the order [P(C 6H 5) 3] 2N + > K + > Na + > Li +. No formyl complexes were isolated and no spectroscopic evidence for formyl formation was observed in the reactions of the other transition metal carbonyls with several hydride sources. Fe(CO) 4-P(C 6H 5) 3 gave K 2Fe(CO) 4 when treated with KHB(OCH 3) 3. When treated with LiBH(C 2H 5) 3, W(CO) 6 gave a mixture of HW 2(CO) 10?and (OC) 5W(COC 2H 5) ?; the latter was methylated to give the carbene complex (OC) 5WC(OCH 3)C 2H 5. 相似文献
16.
运用脉冲激光光解-激光诱导荧光(PLP-LIF)的方法在293-573 K的温度范围内测量了C 2(X 1Σ g+)自由基与不饱和碳氢化合物(C 2H 4和C 2H 2)气相反应的双分子反应速率常数. 获得的速率常数可以用Arrhenius 公式表达如下(单位: cm 3·molecule -1·s -1): k(C 2H 4)=(1.16±0.10)×10 -10exp[(290.68±9.72)/T], k(C 2H 2)=(1.36±0.02)×10 -10exp[(263.85±7.60)/T], 误差为2σ. 由获得的双分子反应速率常数及其所呈现的负温度效应, 我们认为在293-573 K温度范围内C 2(X 1Σ g+)自由基和不饱和碳氢化合物的反应遵循加成机理. 相似文献
17.
The tandem quadrupole photodissociation mass spectrometer has been used to study photodissociation reactions of Ar +2, Ne +2, and (CO 2) +2. The cross sections for photodissociation of Ar +2 exhibited a strong dependence on ion source pressure, varying from 2 × 10 ?18cm 2 at 0.1 torr to 6 × 10 ?19cm 2 at 0.5 torr. A large photodissociation cross section (2 × 10 ?17cm 2 for the reaction (CO 2) +2 → CO +2+ CO 2 was observed at the red end of the visible spectrum (580–620 nm) suggesting that this may be an important reaction in CO 2 rich planetary ionspheres such as that of Mars. 相似文献
18.
The kinetic energy released in near-thermal charge-transfer reactions of Ar + and N 2+ with NO, O 2, CO, H 2O, N 2O, CO 2 and NH 3 has been measured. The partitioning between kinetic and internal modes is found to be very similar for most of the Ar +/N 2+ pairs. Two hypotheses to explain this similarity are proposed and discussed. 相似文献
19.
The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H* over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^*, which reacted with adsorbed CO subsequently via CO^*+OH^* → CO2^*+H^*; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^*+2H^* → CH^*+OH^*. The formation of the surface species (CH) from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis. 相似文献
20.
Surface-induced interactions of the projectile ion C 2D 4+ with room-temperature (hydrocarbon covered) stainless steel, carbon highly oriented pyrolytic graphite (HOPG), and two different
types of diamond surfaces (O-terminated and H-terminated) were investigated over the range of incident energies from a few
eV up to 50 eV. The relative abundance of the product ions in dependence on the incident energy of the projectile ion [collision-energy
resolved mass spectra, (CERMS) curves] was determined. The product ion mass spectra contained ions resulting from direct dissociation
of the projectile ions, from chemical reactions with the hydrocarbons on the surface, and (to a small extent) from sputtering
of the surface material. Sputtering of the surface layer by low-energy Ar + ions (5–400 eV) indicated the presence of hydrocarbons on all studied surfaces. The CERMS curves of the product ions were
analyzed to obtain both CERMS curves for the products of direct surface-induced dissociation of the projectile ion and CERMS
curves of products of surface reactions. From the former, the fraction of energy converted in the surface collision into the
internal excitation of the projectile ion was estimated as 10% of the incident energy. The internal energy of the surface-excited
projectile ions was very similar for all studied surfaces. The H-terminated room-temperature diamond surface differed from
the other surfaces only in the fraction of product ions formed in H-atom transfer surface reactions (45% of all product ions
formed versus 70% on the other surfaces). 相似文献
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