Dynamic Renner effect in collisions of C+ with H2

The dynamic Renner effect is shown to permit formation of CH⁺₂ in its first excited (²B₁) state from low energy collisions of C⁺ + H₂. The consequences for C⁺ + H₂. The consequences for C⁺ + H₂ radiative association are discussed.     

A further study of the near-thermoneutral reactions O2H+ + H2 ⇌ H3+ + O2

The forward and reverse rate coefficients for the reactions (1) O₂H⁺ + H2 ? H₃⁺ + O₂ and (2) O₂D⁺ + D₂ ? D₃⁺ + O₂ have been determined in a SIFT at 80 and 300 K, from which values of the enthalpy and entropy changes in the reactions have been obtained. The data indicate that the proton affinity of H₂ is greater than that of O₂ by 0.33 ± 0.04 kcal mole^?1; similary, the deuteron affinity of D₂ is 0.35 ± 0.04 kcal mole^?1 greater than that of O₂. The measurements of entropy changes confirm that O₂H⁺ has a triplet electronic ground state.     

A low-energy passage for C+ + H2 → CH+(1Σ+) + H

Ab initio (SCF and CI) calculations have been performed for the linear approach (C_∝v) of C⁺ to H₂. For the ² Σ⁺ surface the saddle point and barrier height were determined. The interaction of the ²Σ⁺ and ²Π surfaces was investigated, leading to the conclusion that in near-C_∝v symmetry a low-energy path exists by which CH⁺¹ Σ⁺ can be formed, with negligible barrier in excess of endothermicity.     

On the mechanism of the ion-molecule reaction CH3+ + CH4 = C2H5+ + H2

Experimental evidence supporting the “direct” reaction model and the “intermediate complex” model for the reaction CH₃⁺(CH₄, H₂)C₂H₅⁺ 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.     

Endothermic reactions of Ni+ with H2, HD and D2

An ion-beam apparatus is employed to study the reaction of Ni⁺ with H₂, HD, and D₂ as a function of kinetic energy. These reactions lead to the endothermic formation of NiH⁺, NiH⁺ and NiD⁺, and NiD⁺, respectively. Interpretation of the threshold for these processes yields the average bond energies, D⁰(Ni⁺H) = 1.86 ± 0.09 eV and D⁰(Ni⁺D) = 1.90 ± 0.14 eV. The total reaction cross sections for all three systems are similar; however, a striking isotope effect is observed for Ni⁺ reacting with HD. The dependence of the cross sections on relative kinetic energy is discussed in terms of simple models for reaction.     

Quantum mechanical treatment of the collinear H+ + H2 system. The uncoupled system

A fully converged close coupling study is performed of the collinear (H⁺ + H₂) system on the lower potential energy surface. The surface is derived by the DIMZO (diatomic in molecules-zero overlap) method. Transition probabilities for the reactions: H⁺ + H₂ (ν = 0, 1) → H₂ (ν′) + H⁺; ν′ = 0,..., 7 are given for a number of total energies in the range from 1 eV to 3 eV. It is found that for this energy region the transition ν = 0 → ν′ = 0 is the most preferential. This fact leads us to believe that addition of the upper surface will have a minor effect on the calculated probabilities of transitions from ν = 0 in the above-mentioned energy range.     

A State-selected study of the symmetric charge transfer reaction H2+ + H2

We have measured the relative total charge transfer cross sections of H₂⁺ + H₂ as a function of the vibrational state of H₂⁺, υ′_o = 0–4. using the crossed ion-neutral beam and high-resolution photoionization methods. The experimental results obtained at a center-of-mass collisional energy of 22.5 eV are found to be in excellent agreement with a recent theoretical study.     

Laser control of potential energy surface crossing in ion-molecule reactions application to Na+ + CH4

Laser ion-molecule reaction interaction through dipole moments leads to potential energy sur-face crossings. We will show here by using gauge representation (electric field gauge) that we can induce laser promoted surface crossing in the region (2 a.u.) where the dipole moment changes sign. We illustrate such effects for the NaH + CH₃⁺ ↔ Na⁺ + CH₄ reaction which takes the form of inverted Morse potential (without a barrier) using ab initio methods for calculating the reaction path and the permanent dipole moment of this ion-molecule reaction.     

Predissociation of the C2Σu+ state of N2+

Two mechanisms for the predissociation of the C²Σ_u⁺ state of N₂⁺ are discussed - the accidental mechanism and a direct, homogeneous process C → B²Σ_u⁺. The matrix elements for the latter channel are dominated by a contribution from the nuclear kinetic energy operator, containing a Franck-Condon integral of form 〈?|?/?R|υ′〉.     

Excitation and decay of the C2Σ+u state of N+2 following collisions of He+ ions with N2 isotopes

A quantitative analysis is made of the N⁺₂ “2nd negative” emission (“2N”: C²Σ⁺_u → X²Σ⁺_g) produced by the impact of 500 eV to 25 keV He⁺ beams on ¹⁴N₂, ¹⁴N¹⁵N and ¹⁵N₂. Above about 5 keV, the relative 2N emission rates from the various vibrational levels of the C state are the same as those observed for ? 2 keV Ne⁺, or > / 90 eV electron-impact. These limiting distributions are compared to those predicted for a Franck-Condon excitation of the C state, modified by configuration interaction. The weakening in 2N emission at the vibrational levels ν′ > / 3 is ascribed to spontaneous C-state predissociation. The data fully confirm recent reports that this predissociation extends over a wide range of ν′ and that it is subject to a strong isotope effect. The ratios of the rates of C-state predissociation to 2N emission are obtained for the levels ν′ = 3 to 8 of each nitrogen isotope. By means of these data it is shown that near-resonant charge transfer dominates the distribution of vibrational excitation probabilities only at energies below about 10 eV. A comparison is made of absolute cross-sections for C-state emission with those for N⁺ and N⁺₂ production in He⁺/¹⁴N₂ collisions at energies between 5.5 eV and 25 keV.     

The H2 elimination reactions of Ã2B3g C2H4+ and C2D4+

Kinetic energy releases from the unimolecular H₂ (D₂) elimination reactions of energy-selected òB_3gC₂H₄⁺(C₂D₄⁺) 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.     

Electronic nonadiabatic transitions in the reactive (Ar+ + H2, Ar + H+2, ArH+ + H) system. Numerical results for the collinear configuration

In this communication are presented exact quantum mechanical nonadiabatic electronic transition probabilities for the collinear reaction Ar⁺ + H₂(v_i = 0) → ArH⁺(v_f) + 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 v_i = 0 of the Ar⁺ + H₂ system and v_i = 2 of the Ar + H⁺₂ system. The threshold for the reaction is found to be 0.06 eV.     

Collision rotational transfers in NaH A1Σ+ by He,Ar or H2 (and in KH A1Σ+ by H2)

The total and relative rotational transfer cross sections σ_total and σ_Ji-Jf, by collisions of NaH A¹Σ with He, Ar or H₂, are measured from υ′ = 4 and υ′ = 11, J₁′ = 6. The σ_total increase as υ′ increases. They are similar for He and H₂ but much greater for Ar especially at large υ′. In NaH A¹Σ⁺ the bond goes from covalent to ionic as υ′ increases: σ_total is very sensitive to an attractive potential due to the interaction of the permanent electric dipole moment of the molecule with the polarizability of the atom (α_Ar = 11 au, α_He = 1.37 au). The σ_Ji-Jf decrease monotonously as |J_f-J_i| increases and may be fitted by a scaling law. The variation with ΔJ depends on the colliding gas but does not change appreciably with υ′: most of the transfers could take place on the repulsive part of the interaction potential, the shape of which would not depend on υ′.     

The dynamics of Cl− + H2 reactive collisions

A multicoincidence analysis of the crossed beam Cl^? + H₂ system in the 5.6–12 eV energy range has shown the existence of four different product channels: reaction (R), reactive detachment (RD), simple detachment (SD) and dissociative detachment (DD). For the whole energy range both R and RD channels give rise to HCl molecules at a unique and common center-of-mass scattering angle whereas the vibrational excitation probability of HCl obeys completely different rules for each channel: v ≤3 in channel R and equal probability in all possible vibrational levels in RD. A Thomas-type collision model joined to curve crossing with an intermediate autodetaching HCl^? state accounts well for all of the experimental findings.     

An ab initio potential energy surface for the reaction N+ + H2 → NH+ + H

Preliminary results of ab initio unrestricted Hartree-Fock calculations for the potential energy surface for the reaction N⁺ + H₂ → NH⁺ + H are reported. For the collinear approach of N⁺ to H₂, the ³Σ^? surface has no activation barrier and has a shallow well (ca. 1 eV). For perpendicular approach (C_2v symmetry) the ³B₂ state is of high energy, the ³A₂ state has a shallow well but as the bond angle increases the ³B₁ state decreases in energy to become the state of lowest energy. Neither the collinear nor the perpendicular approaches give adiabatic pathways to the deep potential well of ³B₁ (HNH)⁺.     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).

     

Structure and properties of H2CN,H2CC−, H2BO and H2CO+

Ab initio SCF—MO calculations are presented for H₂CN, H₂CC^?, H₂BO and H₂CO⁺, including geometry optimization. One-electron properties are presented and compared with experiment where possible, particularly ESR hyperfine data.     

Al(2Pu)+H2(X1Σ+g)的分子反应动力学

基于多体展式方法所导出的ＡｌＨ２（Ｘ＾２Ａ１）分析势能函数,用准经典的Ｍｏｎｔｅ－Ｃａｒｌｏ轨迹法对Ａｌ（＾２Ｐｕ）＋Ｈ２（Ｘ＾１∑＾＋ｇ,ｕ＝ｊ＝０）的分子反应动力学过程进行了计算。结果表明,此反应的主产物为交换反应Ａｌ（＾２Ｐｕ）＋Ｈ２（Ｘ＾１∑＾＋ｇ,ｖ＝ｊ＝０）→ＡｌＨ（Ｘ＾１∑＾＋,Ｖ’,ｊ’）＋Ｈ（＾２Ｓｇ）的ＡｌＨ（Ｘ＾１∑＾＋,ｖ’,ｊ’）没有发现ＡｌＨ２（Ｘ＾２Ａ１）的络合物。而     

Computed potential hypersurface (including electron correlation) of the system Li+/H2

The potential hypersurface of the system LiH₂* is calculated in the Hartree—Fock approximation and with the IEPA PNO method (including electron correlation). The basis set consists of gaussian lobes. The region of HH distances considered is 0.9 to 3 a_o (occasionally to 5 a_o) whereas the distance of the Li nucleus to the midpoint of the H₂ subunit is varied between 1 and 15 α_o. The angular dependence of the hypersurface is investigated as well. The maximum overall error (except for a parallel shift of the whole hypersurface) is estimated to be less than 0.002 au and even smaller in more limited regions of space. The role of the correlation energy is discussed and the asymptotic behaviour of the Li⁺/H₂ interaction is compared with results from perturbation theory. The results are given both as tables of numbers in the form of an analytic fit. The change of energy, equiblirium distance and force constant of the H₂ as a function of the approach of the Li⁺ is also tabulated.     

硫酸溶液中电化学改性石墨电极对Fe3+/Fe2+的电催化性能与准电容特性

通过循环伏安(CV)、恒电流充放电和电化学阻抗谱(EIS)等测试方法,研究了电化学改性石墨电极对硫酸溶液中Fe3+/Fe2+的电催化性能与准电容特性.结果表明:由于电化学改性石墨电极表面存在大量的含氧活性官能团,使其对Fe3+/Fe2+的氧化还原反应具有极高的电催化性能,并具有可逆反应过程特征.在含有0.5mo·lL-1Fe3++0.5mo·lL-1Fe2+的2.0mo·lL-1H2SO4溶液中,其表观面积比电容是不含铁离子硫酸溶液的1.808倍,达到2.157F·cm-2;同时,铁离子浓度的增大也能够进一步提高其电容量.Fe3+/Fe2+电对的加入增加了充放电时间,有效提高了电化学电容器(EC)的电容存储容量和高功率特性.电化学阻抗谱测试同样证实体系具有明显的电容特性.因此,可以利用电化学改性石墨电极表面的含氧活性官能团和溶液中Fe3+/Fe2+的氧化还原特性来共同储存和释放能量.