Efficient Preparation of D2 Molecules in v=2 by Stimulated Raman Pumping

We report the preparation of D₂ molecules in v=2 level in molecular beam condition. A single longitudinal mode laser system was used for excitation of D₂ from (v=0, j=0) to (v=2, j=0) with the scheme of stimulated Raman pumping. An excitation efficiency of 25.2% has been achieved, which was determined by the scheme of resonance-enhanced multiphoton ionization. Dependence of relative excitation efficiency on laser energy has been measured. We found that the increasing rate of excitation efficiency became slower as pulse energy of Stokes laser increase, while the excitation efficiency still increases approximately linearly with pump pulse energies up to 60 mJ. The spectral line shapes of Raman transition was also measured at different laser energies and considerable dynamical Stark effect was observed. A single peak was found on the three dimension surface of relative excitation efficiency, indicating the process occurred in the present study is a process of stimulated Raman pumping instead of stimulated adiabatic Raman passage.     

Studies on some exponential‐screened coulomb potentials

The generalized pseudospectral method is used to study the bound‐state spectra of some of the exponentially screened Coulomb potentials, namely, the exponential cosine screened Coulomb (ECSC) and general exponential screened Coulomb (GESC) potential, with special emphasis on higher states and stronger interaction. Eigenvalues accurate up to 11 significant figures are obtained through a nonuniform optimal spatial discretization of the radial Schrödinger equation. All the 55 eigenstates of ECSC potential with n ≤ 10 and 36 eigenstates of GESC potential with n ≤ 8 are considered for arbitrary values of the screening parameter, covering a wide range of interaction. Excited states as high as up to n = 18 have been computed with high accuracy for the first time. Excellent agreement with the literature data has been observed in all cases. All the GESC eigenstates are calculated with much greater accuracy than the existing methods available in literature. Many l ≠ 0 states of this potential are reported here. In both cases, a detailed variation of energies with respect to the parameters in potential is monitored. © 2012 Wiley Periodicals, Inc.     

Intramolecular Mobility in the Complexes 2SbCl3· p-C6H4(CH3)2and SbCl3· C6H5COCH3according to 35Cl NQR Data

Temperature dependences of the ³⁵Cl and ¹²¹Sb spin-lattice relaxation time ₁in antimony trichloride complexes with p-xylene and acetophenone were studied using NQR spectroscopy. The activation energies of the retarded motion (similar to that discovered in some v complexes of SbCl₃) of chlorine atoms were determined from the ³⁵Cl ₁(T) function. New data on the shape of the ¹²¹Sb ₁(T) function are discussed.     

Quantum chemical study of the structure of bicyclo[2.2.0]hex-1(4)-ene and its dimers

The RHF, B3LYP, and PBE0/6-311G** quantum chemical methods are used to determine the point symmetry group and the equilibrium structure of bicyclo[2.2.0]hex-1(4)-ene (I, D _2h ), its two stable dimers (tricyclo[4.2.2.2^2,5]dodeca-1.5-diene (II, D _2h ) and 2,5-dimethylenetricyclo[4.2.2.0^1,6]decane (III, C ₂)), and pentacyclo [4.2.2.2^2,5]dodecane (IV, D ₂) that is a hypothetical intermediate in the dimerization reaction of the molecules of I. The relation of total energies is obtained with regard to zero-point vibrations: E(III) < E(II) ≪ E(IV) ≪ 2E(I).     

Crossed Molecular Beam Study of the F+D2(v=1, j=0) Reaction

The reaction dynamics of the fluorine atom with vibrationally excited D₂(v=1, v=0) was investigated using the crossed beam method. The scheme of stimulated Raman pumping was employed for preparation of vibrationally excited D₂ molecules. Contribution from the reaction of spin-orbit excited F^?(²P_1/2) with vibrationally excited D₂ was not found. Reaction of spin-orbit ground F(²P_3/2) with vibrationally excited D2 was measured and DF products populated in v‘=2, 3, 4, 5 were observed. Compared with the vibrationally ground reaction, DF products from the vibrationally excited reaction of F(²P_3/2)+D₂(v=1, j=0) are rotationally “hotter”. Differential cross sections at four collision energies, ranging from 0.32 kcal/mol to 2.62 kcal/mol, were obtained. Backward scattering dominates for DF products in all vibrational levels at the lowest collision energy of 0.32 kcal/mol. As the collision energy increases, angular distribution of DF products gradually shifts from backward to sideway. The collision-energy dependence of differential cross section of DF(v’=5) at forward direction was also measured. Forward-scattered signal of DF(v'=5) appears at thecollision energy of 1.0 kcal/mol, and becomes dominated at 2.62 kcal/mol.     

氮苄叉基苯胺分子的平面扭曲驱动力的DFT研究

为了探索DFT方法中氮苄叉基苯胺分子的扭曲驱动力, 通过把非平面氮苄叉基苯胺(NBA)分子的DFT能量分成π和σ的方法, 分析了垂直离域能ΔE^V(θ)及σ-π轨道作用能ΔE^σπ(θ)的失稳定性, 并讨论了在扭曲过程中它们所起的作用. 在B3LYP/6-31G*, 6-311G*, 6-31G(2d), 6-311G(2d)水平下的计算结果显示: 与经典观点不同, π电子的离域是失稳定的, 且平面时失稳定性最强, 是分子扭曲的动力; 但σ-π轨道作用也是失稳定的, 随着扭角的增大其失稳定性增强, 是分子扭曲的阻力. NBA分子的大扭角构象, 是包含π-π, σ-π轨道作用在内的各种电子相互作用共同作用的结果.     

A generalized formula for the energies of alternant molecular orbitals. II. Heteronuclear molecules

Using the method of alternant molecular orbitals (AMO ), it is shown that the energies of AMOS (E_kσ) for an arbitrary heteronuclear alternant system, having a singlet ground state, are connected with the energies of MOS (e_{k(k )}) obtained by means of the conventional Hartree–Fock (HF ) method (SCF -LCAO -MO -PPP ) via the formula: In the general case, the determination of the correlation corrections δ_i,kσ is connected with the solving of a complicated system of integral equations, which is considerably simplified if the Hubbard approximation is accepted for the electron interaction. The energy spectrum of a chain with two atoms in the elementary cell (AB)_n is considered as an example. It is shown that if nontrivial solutions exist (δ_i,kσ ≠ 0), the correlation correction for AMOS of different spin are different (δ_i,kσ ≠ δ_i,kβ), from which it follows, that the width of the energy gap ΔE_∞ for AMOS with different spin is different: ΔE_∞,α ≠ ΔE_∞,β.     

Atomic Xα calculations based on EHFS(α) = Eexp

The total energies and one-electron energies for first- and second-row atoms were calculated by using the Hartree–Fock and the Hartree–Fock-Slater Hamiltonian with X_α orbitals, u_i(α_exp); α was parametrized from E^HFS (α_exp) = E^exp. The E^HF (α_exp) total energies are always higher than the Hartree–Fock energies for the atoms. The relation of the calculated ionization potential to the experimental ionization potential depends on the α used to define u_i(α), α_exp, or α_HF.     

Darstellung und Schwingungsspektren von Chloro-Bromo-Dirhodaten(III), [Rh2ClnBr9−n]3−, n = 0–9

Preparation and Vibrational Spectra of Nonahalogenodirhodates(III), [Rh₂Cl_nBr_9-n]^3?, n = 0–9 The pure nonahalogenodirhodates(III), A₃[Rh₂Cl_nBr_9-n], A = K, Cs, (TBA); n = 0–4, 9, have been prepared. They are formed from the monomer chlorobromorhodates(III), [RhCl_nBr_6-n]^3?, n = 0–6, which are bridged to confacial bioctahedral complexes by ligand abstraction in less polar organic solvents. From the mixtures the complexions are separated by ion exchange chromatography on DEAE-cellulose. The solid, air-stable, air-stable, K-, Cs- and (TBA)-salts of [Rh₂Cl_nBr_9-n]^3?, n = 0–4, are green, of [Rh₂Cl₉]^3? are brown. The IR and Raman spectra of [Rh₂Br₉]^3? and [Rh₂Cl₉]^3? are assigned according to the point group D_3h. The chlorobromodirhodates exist as mixtures of geometrical and structural isomers, which belong to different point groups. The vibrational spectra exhibit bands in characteristic regions; at high wavenumbers stretching vibrations with terminal ligands v(Rh—Cl_t): 360–320, v(Rh—Br_t): 280–250; in a middle region with bridging ligands v(Rh—Cl_b): 300–270, v(Rh—Br_b): 210–170 cm^?1; the deformation bands are observed at distinct lower frequencies. The terminal ligands are fixed very strong, and the distance between v(Rh—X_t) and v(Rh—X_b) increases with decreasing size of the cations.     

Identification of unknown diffusion coefficient in pure diffusive linear model of chronoamperometry. I. The theory

Coefficient identification problem for diffusion equation u _t (x, t) = (D(x)u _x (x, t)) _x arising in chronoamperometry is studied. The adjoint problem approach is developed for the case when the output measured data is given in the form of left/right flux. Analytical formulas for determination of the values D(0), D(L) at the endpoints x = 0; L, of the unknown coefficient D(x), via the solution v(x, t) of the constant coefficient equation v _t (x, t) = D v _xx (x, t) is obtained. The integral identity relating solutions of the forward and corresponding adjoint problems is derived. This integral identity permits one to prove the monotonicity and invertibility of input-output map, as well as formulate the gradient of the cost functional via the solutions of the direct and adjoint problems.     

The (n,n)-graphs with the first three extremal Wiener indices

Let G = (V, E) be a simple connected graph with vertex set V and edge set E. The Wiener index W(G) of G is the sum of distances between all pairs of vertices in G, i.e., , where d _G (u, v) is the distance between vertices u and v in G. In this paper, we first give a new formula for calculating the Wiener index of an (n,n)-graph according its structure, and then characterize the (n,n)-graphs with the first three smallest and largest Wiener indices by this formula.     

Direct approximation of the long- and short-range components of the exchange-correlation Kohn-Sham potential

An approximation scheme was developed for the Kohn-Sham exchange-correlation potential v_xcσ, making use of a partitioning of v_xcσ into a long-range screening v_scrσ and a short-range response v_resp component. For the response part, a model v^mod_respσ was used, which represents v_resp as weighted orbital density contributions, the weights being determined by the orbital energies. v^mod_respσ possesses the proper short-range behavior and the atomic-shell stepped structure characteristic for v_resp. For the screening part, two model potentials v^mod_scrσ were used, one with the accurate Slater potential; the other one with the generalized gradient approximation (GGA) for the exchange part. Both use the GGA for the Coulomb correlation contribution to v_scrσ. The scheme provides an adequate approximation to v_xcσ in the outer-valence region with both the proper asymptotics and a rather accurate estimate of the ionization potential from the highest one-electron energy and a reasonable estimate of atomic E_xc and total energies E_tot. © 1997 John Wiley & Sons, Inc.     

Fulfillment of the Conditions of Thermodynamic Equilibrium in an Ice/Electrolyte Solution System with Constrained Geometry

For small volumes of a NaCl solution (10^–6 cm³) with concentrations of 0.1 and 1 M, temperature dependences of the length lof solution columns frozen in thin quartz capillaries (5–10 m in radius) are obtained. At the temperatures t above –4 and –8°C (for 0.1 and 1 M solutions, respectively), the l(t) dependences are reversible, independent of the direction of changes in temperature, and, hence, correspond to the equilibrium conditions of ice/solution system. From the constant mass condition of the solute, an expression for l(t) is derived that includes only one thermodynamic characteristic, namely, the temperature dependence of the solution concentration in equilibrium with ice. Deviations from the calculated l(t) dependences are observed at a temperatures below –2 and –5°C (for 0.1 and 1 M solutions, respectively), which can be explained by the adhesion of frozen solution to the capillary walls. The arising internal stresses lead to the deviations from the thermodynamic equilibrium conditions known for the bulk systems. On approaching the melting zone, the adhesion is failed because of the formation of thin nonfreezing water interlayers on the quartz surface.     

Hosoya index of unicyclic graphs with prescribed pendent vertices

The Hosoya index z(G) of a (molecular) graph G is defined as the total number of subsets of the edge set, in which any two edges are mutually independent, i.e., the total number of independent-edge sets of G. By G(n, l, k) we denote the set of unicyclic graphs on n vertices with girth and pendent vertices being resp. l and k. Let be the graph obtained by identifying the center of the star S _n-l+1 with any vertex of C _l . By we denote the graph obtained by identifying one pendent vertex of the path P _n-l-k+1 with one pendent vertex of . In this paper, we show that is the unique unicyclic graph with minimal Hosoya index among all graphs in G(n, l, k).      

Thermodynamic Properties of N-(Trimethylsily)ethyleneimine N-(Triethylsily)ethyleneimine and (Dimethylphenylsilyl)ethyleneimine Complexes with Zinc Chloride in the Range 0-340 K

Tmperature dependence of heat capacity of N-(trimethylsilyl)ethyleneimine, N-(triethylsilyl)-ethyleneimine, N-(dimethylphenylsilyl)ethyleneimine with zinc chloride was studied in the 5-340 K rangein an adiabatic vacuum calorimeter with 0.2% error. From the data obtained tge complexes thermodynamicfunctions C0 _p(T), H ⁰(T)-H ⁰(0), S ⁰(T)-S ⁰(0) and G ⁰(T)-H ⁰(0) are obtained in the 0-340 K, as well as fractal dimensions D and characteristic temperatures max for the functions of gractal heat capacity of solid substances.     

Pressure and temperature effects on the excess deuteron and proton conductance

The limiting molar conductances ° of deuterium chloride DCl in D₂O were determined as a function of pressure and temperature in order to examine the proton-jump mechanism in detail. The excess deuteron conductances °_E(D ⁺), as estimated by the equation [°_E(D ⁺) = °(DCl/D ₂ O) – °(KCl/D ₂ O)], increases with an increase in the pressure and temperature as well as the excess proton conductance [°_E(H ⁺) = °(HCl/H ₂ O) – °(KCl/H ₂ O)]. The isotope effect on the excess conductances, however, depends on the pressure and temperature contrary to the model proposed by Conway et al.: °_E(H ⁺)/°_E(D ⁺) decreases with increasing pressure and temperature. The magnitude of the decrease with pressure becomes more prominent at lower temperature. These results are discussed in terms of the pre-rotation of adjacent water molecules, the bending of hydrogen bonds with pressure, and the difference in strength of hydrogen bonds between D₂O and H₂O.     

Activation of C2H6, C3H8, HC(CH3)3, and c-C3H6 by gas-phase Ru+ and the thermochemistry of Ru-ligand complexes

The reactions of Ru⁺ with C₂H₆, C₃H₈, HC(CH₃)₃, and c-C₃H₆ at hyperthermal energies have been studied using guided ion beam mass spectrometry. It is found that dehydrogenation is efficient and the dominant process at low energies in all four reaction systems. At high energies, C-H cleavage processes dominate the product spectrum for the reactions of Ru⁺ with ethane, propane, and isobutane. C-C bond cleavage is a dominant process in the cyclopropane system. The reactions of Ru⁺ are compared with those of the first-row transition metal congener Fe⁺ and the differences in behavior and mechanism are discussed in some detail. Modeling of the endothermic reaction cross sections yields the 0-K bond dissociation energies (in eV) of D ₀(Ru-H)=2.27±0.15, D ₀(Ru⁺-C)=4.70±0.11, D ₀(Ru⁺-CH)=5.20±0.12, D ₀(Ru⁺-CH₂)=3.57±0.05, D ₀(Ru⁺-CH₃)=1.66±0.06, D ₀(Ru-CH₃)=1.68±0.12, D ₀(Ru⁺-C₂H₂)=1.98±0.18, D ₀(Ru⁺-C₂H₃)=3.03±0.07, and D ₀(Ru⁺-C₃H₄)=2.24±0.12. Speculative bond energies for Ru⁺=CCH₂ of 3.39±0.19 eV and Ru⁺=CHCH₃ of 3.19±0.15 eV are also obtained. The observation of exothermic processes sets lower limits for the bond energies of Ru⁺ to ethene, propene, and isobutene of 1.34, 1.22, and 1.14 eV, respectively.     

Reactions of Hf, Ta, and W with O2 and CO: Metal carbide and metal oxide cation bond energies

The reactions of Hf⁺, Ta⁺, and W⁺ with O₂ and CO are studied as a function of translational energy in a guided ion beam tandem mass spectrometer. All three reactions with O₂ form diatomic metal oxide cations in exothermic reactions that occur at the collision rate. In the CO systems, formation of both diatomic metal oxide and metal carbide cations is observed to be endothermic. The energy-dependent cross sections in the latter systems are interpreted to give 0 K bond energies (in eV) of D₀(HfC⁺) = 3.19 ± 0.03, D₀(TaC⁺) = 3.79 ± 0.04, D₀(WC⁺) = 4.76 ± 0.09, D₀(HfO⁺) = 6.91 ± 0.11, D₀(TaO⁺) = 7.10 ± 0.12, and D₀(WO⁺) = 6.77 ± 0.07. The present experimental values for TaO⁺ and WC⁺ agree well with literature thermochemistry, those for HfO⁺ and WO⁺ refine the available literature bond energies, and those for HfC⁺ and TaC⁺ are the first measurements available. The nature of the bonding in MO⁺ and MC⁺ is discussed and compared for these three metal ions and analyzed using theoretical calculations at a B3LYP/HW+/6-311+G(3df) level of theory. Bond energies for all MO⁺ and MC⁺ species are calculated using geometries calculated at this level and single point energies determined at B3LYP, CCSD, CCSD(T), QCISD, and QCISD(T) levels of theory with the same basis set. Reasonable agreement between the theoretical and experimental bond energies for the three metal oxide and three metal carbide cations is found. Potential energy surfaces for reaction of the metal cations with CO are also calculated at the B3LYP level of theory and reveal additional information about the reaction mechanisms.     

Energy resonance and inverse population of the product vibrational states for the reaction F + H2(v = 0) → HF(v′) + H,LCAC‐SW theoretical quantum scattering study

LCAC‐SW (linear combination of arrangement channel‐scattering wavefunction) method was used to calculate collinear state‐to‐state reaction probabilities for the reaction F + H₂(v = 0) → HF(v′) + H on the 6SEC potential energy surface. The results show that reaction probabilities P₀₂ and P₀₃ [i. e., v′ = 2,3 for reaction F + H₂ (v = 0) + HF(v′) + H] are primary, the population of product vibrational states is inverse and the reaction probabilities are oscillatory with collision energies, i.e., there is energy resonance in this reaction, which agrees with a new experiment.     

Ordering chemical unicyclic graphs by Wiener polarity index

Suppose G is a chemical graph with vertex set V(G). Define D(G) = {{u, v} ⊆ V (G) | d _G (u, v) = 3}, where d _G (u, v) denotes the length of the shortest path between u and v. The Wiener polarity index of G, W _p (G), is defined as the size of D(G). In this article, an ordering of chemical unicyclic graphs of order n with respect to the Wiener polarity index is given.