共线散射体系A+BC的平-振能量传递──无限维李代数处理方法

利用无限维李代数方法处理了在BC分子能谱中含有二级与三级非简谐项的散射体系A＋BC的平-振能量传递问题，获得了散射过程的含有主要动力学参量的跃迁矩阵元和跃迁几率的解析表达式     

A transition state view on reactive scattering: initial state-selected reaction probabilities for the H + CH4 → H2 + CH3 reaction studied in full dimensionality

Initial state-selected reaction probabilities for the H+CH(4)→H(2)+CH(3) reaction are computed for vanishing total angular momentum by full-dimensional calculations employing the multiconfigurational time-dependent Hartree approach. An ensemble of wave packets completely describing reactivity for total energies up to 0.58 eV is constructed in the transition state region by diagonalization of the thermal flux operator. These wave packets are then propagated into the reactant asymptotic region to obtain the initial state-selected reaction probabilities. Reaction probabilities for reactants in all rotational states of the vibrational 1A(1), 1F(2), and 1E levels of methane are presented. Vibrational excitation is found to decrease reactivity when reaction probabilities at equivalent total energies are compared but to increase reaction probabilities when the comparison is done at the basis of equivalent collision energies. Only a fraction of the initial vibrational energy can be utilized to promote the reaction. The effect of rotational excitation on the reactivity differs depending on the initial vibrational state of methane. For the 1A(1) and 1F(2) vibrational states of methane, rotational excitation decreases the reaction probability even when comparing reaction probabilities at equivalent collision energies. In contrast, rotational energy is even more efficient than translational energy in increasing the reaction probability when the reaction starts from the 1E vibrational state of methane. All findings can be explained employing a transition state based interpretation of the reaction process.     

The accuracy of transition state theory in its absolute rate theory and variational formulations

The accuracy of the absolute rate theory and variational formulations of transition state theory have been determined for a series of collinear reactions A + BC → AB + C on the Porter—Karplus potential energy surface by comparing theoretical values of classical mean reaction probabilities with classical mechanical trajectory results.     

A quantum-mechanical investigation of collinear models for collision-induced dissociation

Accurate quantum-mechanical wavepacket results are reported for two collinear A + BC → A + B + C dissociation models. Both systems are of the MO EXP (Morse oscillator, exponentially repulsive interaction) type and thus do not allow for the possibility of reaction. One of these models has been previously subjected to a semiclassical study by Rusinek and Roberts. In the present paper, dissociation probabilities from vibrational states υ = 0, 1 and 3 of the diatomic are reported in a wide energy range for both systems. Numerous state-to-state transition probabilities are also given and the results are compared to those of related studies.     

Investigations with the finite element method on the Cyber 205

We are trying to investigate systematically the application of the finite element method (FEM) for solving the Schrödinger equation. The present paper is devoted to the calculation of vibrational transition probabilities for the collinear reactive system A + BC (i.e. H+H₂ and their isotopes). The calculations are fully two-dimensional and the results are compared with earlier FEM calculations and conventional basis set expansion methods using the the R-matrix or S-matrix propagation.We made extensive analysis of FEM on the vector-computer Cyber 205 and developed a vector code for the efficient use in two dimensions, so that in the near future applications even in three dimensions will be possible.For the hydrogen exchange reactions we investigated the following isotope combinations: (a) H + H₂, b) H + DH, D + HD and H + MuH (symmetric reaction), (c) D + HH, H + DD and Mu + DD (asymmetric reaction). We calculated the transition probabilities for up to five open vibrational channels and found excellent agreement with known exact values.     

Violation of microscopic reversibility and the use of reverse quais-classical trajectories for calculating reaction cross sections

In order to calculate the transition probabilities (or cross sections) for reactive collisions, such as A + BC(ν, j)→ AB(ν′, j) + C, using the quasi-classical trajectory method, one quantizes the internal energy of the reagents and in addition adopts some algorithm for calculating the internal quantum numbers of the products. A serious consequence of this procedure is that the quasi-classical results do not obey microscopic reversibility. It is shown that for the collinear F + H₂(ν = 0) → FH(ν = 2, 3)+ H reaction (and its D₂ counterpart), the quasi-classical trajectory probabilities for the reverse reaction not only differ substantially from the forward ones but in general are in much better agreement with accurate quantum calculations. A similar situation was found for the collinear H + H₂(0) → H₂(1) + H reaction. We suggest that in doing quasi-classical calculations, the reverse of the process of interest should also be considered. Comparison of forward and reverse quasi-classical collinear calculations with accurate collinear quantum results could give an indication of whether forward or reverse calculations should be used for the three-dimensional case.     

Classical model for electronically non-adiabatic collision processes resonance effects in electronic-vibrational energy transfer

A classical model for electronically non-adiabatic collision processes is applied to E → V energy transfer in a collinear system, A + BC (v = 1) → A¹ + BC (v = 0), resembling Br-H₂.The model, which treats electronic as well as translational, rotational, and vibrational degrees of freedom by classical mechanics, describes the resonance features in this process reasonably well.     

Allowed transitions in silicon isoelectronic ions

Dipole‐allowed transitions have been studied for the first few members of the Si isoelectronic sequence. Transition energies, oscillator strengths, transition probabilities and quantum defect values have been estimated for the low‐ and high‐lying excited states of s and d symmetries up to the principal quantum number n=7 for these 3p open shell ions from P⁺ to Cr¹⁰⁺. Time‐dependent coupled Hartree–Fock (TDCHF) theory has been utilized to calculate such transition properties. Most of the results for transition energies, oscillator strengths, and transition probabilities for higher excited states are new. The transition energies for low‐lying excited states agree well with experimental data wherever available. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

A quantum-mechanical investigation of a collinear model for collision-induced dissociation

Quantum-mechanical wavepacket results are reported for a collinear A + BC → A + B + C dissociation model previously investigated semi-classically by Rusinek and Roberts. The quantum-mechanical and semi-classical probabilities are found to be in very good agreement.     

Analytical solution of vibrational–rotational energy transfer in the dissociation and relaxation of N2, Br2, and CO at high temperature

An approximate analytical solution of relaxation in a low-pressure system with exponential transition probabilities is given for vibrational–rotational energy transfer in the dissociation of diatomics. The main assumption is that the rotational degrees of freedom are in thermal equilibrium at all times, and that the barrier to dissociation in the vibrational–rotational plane is linear and asymmetric. The theory is applied to high-temperature dissociations of N₂, Br₂, and CO in excess argon, with satisfactory agreement with available experimental data.     

Experimental evidence for “cascading”; rapid vibrational relaxation with retention of rotational quantum number

In previous work we have postulated that highly rotationally-excited hydrides, AH, can relax by way of “cascading”, i.e., rapid vibrational exchange in which AH is vibrationally deactivated with retention of rotational quantum number (Δv_AH = ?1, ΔJ_AH ≈ 0). Infrared chemiluminescence studies reported here provide evidence of cascading in OH2 and HCl2 (2 symbolises vibrational excitation in the ground electronic state). The collision partners, BC, responsible for the cascading are thought to be (i) OH2 + NO₂, (ii) HCl2 + NOCl and (iii) HCl2 + ICl. Extremely rapid vibrational exchange is indicative of a resonant process. Resonance must occur for a wide range of v_AH and J_AH, and a variety of collision partners BC. A plausible basis for such a process involves multiquantum vibrational and rotational transitions in the recipient molecule, BC, which “tune” the energy-exchange to resonance.     

On the evaluation of rotational transition probabilities from distribution functions

A method is described for the evaluation of rotational transition probabilities from the nonequilibrium distributions possessed by the products of certain chemical reactions. Results obtained from the method are compared with those provided by theoretical calculation.     

Statistical mechanics of energy transfer in gas–surface scattering: A dynamical Lie algebraic approach

The dynamical Lie algebraic (DLA) method is used to describe statistical mechanics of energy transfer in rotationally inelastic molecule–surface scattering. Statistical average values of an observable for the scattering system are calculated in terms of density operator formalism in statistical mechanics. Employing a cubic expansion procedure of molecule–surface interaction potential leads to generation of a dynamical Lie algebra. Thus these statistical average values as a function of the group parameters can be obtained analytically in this formulation. The group parameters can be found from solving a set of coupled nonlinear differential equations. The DLA method, which has no need for determination of transition probabilities in advance as made routinely in the calculation, offers an efficient alternative to the method for computing the statistical average values. This method is much less computationally intensive because most of calculations can be analytically carried out. The average final rotational energies and their dependence on the main dynamic variables and the average interaction potential are presented for the rotationally inelastic scattering of NO molecules from a flat, static Ag(111) surface. Direct comparison is made between the predictions of this model calculation and experiment. The model reproduces well the degree of rotational excitation and correlation between the average final translational and the average rotational energies. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Quantum dynamics study of Li + HF reaction

We report rigorous quantum dynamics studies of the Li + HF reaction using the time-dependent wavepacket approach. The dynamics study is carried out on a recent ab initio potential energy surface, and state-selected reaction probabilities and cross sections are calculated up to 0.4 eV of collision energy. Many long-lived resonances (as long as 10 ps) at low collision energies (below 0.1 eV) are uncovered from the dynamics calculation. These long-lived resonances play a dominant role in the title reaction at low collision energies (below 0.1 eV). At higher energies, the direct reaction process becomes very important. The reaction probabilities from even rotational states exhibit a different energy dependence than those from odd rotational states. Our calculated integral cross section exhibits a broad maximum near the collision energy of 0.26 eV with small oscillations superimposed on the broad envelope which is reminiscent of the underlying resonance structures in reaction probabilities. The energy dependence of the present CS cross section is qualitatively different from the simple J-shifting approximation, in which a monotonic increase of cross section with collision energy was obtained. Received: 8 January 1997 / Accepted: 14 January 1997     

Rotational—vibrational dipole transitions in HD

The transition moments are computed for several lines in the X¹Σ⁺_g state of HD. The results are obtained by taking into account interactions with Σ_u and Π_u states. It is shown that the latter influence appreciably the transition probabilities in the 00 band. The permanent dipole moment is also computed for several vibrational and rotational states.     

A simple picture for the rotational enhancement of the rate for the F + HCl --> HF + Cl reaction: a dynamical study using a new ab initio potential energy surface

Quantum scattering calculations for the reaction F + HCl --> HF + Cl are performed on a new ground-state ab initio potential energy surface. The reagent rotation is found to have a dramatic effect on the reaction probability. Furthermore, the exit channel rotational thresholds leave a strong imprint on the reaction probabilities and even on the cumulative reaction probability. A very simple vibrationally adiabatic model is shown to account for most aspects of the reaction dynamics. In this model, the fast vibrational motion is adiabatically eliminated leaving the key reaction dynamics represented by a reduced atom + rotor collision. The shape of the adiabatic potential surface immediately yields to a simple and intuitive interpretation for the rotational enhancement of the rate. The rotational enhancement is shown to be an effect of the entrance channel dynamics of the atom-rotor problem.     

牛血清白蛋白-Cu2＋结合过程中盐酸小檗碱的变构效应

用核磁共振(1H NMR)、圆二色谱(CD)、荧光光谱(FS)以及紫外光谱(UV)技术考察了中药有效成分盐酸小檗碱(BC)对牛血清白蛋白(BSA)-Cu2＋结合过程的变构效应, 得到分别表征BSA内源荧光猝灭、BSA-Cu2＋复合物稳定性以及Cu2＋在BSA分子上的结合位点发生变构的定量效应参数βQ (βA和βn)和效率参数γQ (γA和γn). 结果表明, BC对Cu2＋猝灭BSA内源荧光呈负变构效应(0＜βQ＜1), 而对BSA-Cu2＋复合物稳定性以及Cu2＋在BSA分子上的结合位点呈正变构效应(βA＞1, βn＞1); 变构效应随BC浓度增加而增强, BC对BSA-Cu2＋复合物稳定性的变构效率明显高于其对荧光猝灭和结合位点的变构; BSA分子构象转变是变构效应的主要原因.     

Rotational-vibrational rainbows in impulsive electron-diatomic molecule collisions

Rotational and vibrational rainbow effects in electron-diatomic molecule scattering at intermediate impact energies (≈10² eV) are discussed in a simple quantum mechanical spectator model within the rigid rotor/harmonic oscillator approximation. The total vibrational (summed over all final rotational quantum numbers) and rotational (vibrationally summed) transition probabilities show vibrational or rotational rainbow patterns, characteristic steps, and rainbow singularities, which are analyzed and interpreted in terms of classical cross sections.     

Time-dependent Quantum Wave Packet Study of F+HCl and F+DCl Reactions

The F+HCl and F+DCl reactions are studied by the time-dependent quantum wave packet method, using the most recent potential energy surface reported by Deskevich et al.. Total reaction probabilities for a number of initial ro-vibrational states of HCl and DCl diatomic moiety are presented in the case of total angular momentum J=0. It is found that for both reactions the initial rotational excitation of the diatomic moiety enhances greatly the reaction probabilities but this e?ect is more signiˉcant for F+HCl system. This is mainly due to larger rotational constant of the HCl reagent. The initial vibrational excitation of the diatomic moiety has little e?ect on the reactivity for both systems except shifting down the collision energy threshold. The results indicate that the reaction coordinates for these two systems are e?ectively along rotational freedom degree. More quantum phenomena, such as tunneling and resonance, are observed in F+HCl reaction than F+DCl reaction, and for the initial states studied, the reactivity of the later is lower. Di?erent skewing angles of these two systems account for these isotopic di?erences.     

Simultaneous vibrational and rotational transitions in hydrogen + argon at high collision velocities: Collisions at nonzero impact parameters

The problem of vibrationally and rotationally inelastic scattering processes in H₂ + Ar for nonzero impact parameter b has been investigated in the collision velocity range of 10⁶–10⁷ cm/sec by use of the sudden approximation. The simultaneous vibrational (0 → 1) and rotational (00 → 00, 20, or 40) transitions were studied. For υ > 3 x 10⁶ cm/sec, the probabilities for b/l = 1.0 are found to be very large compared with those for b = 0, where l is the hard-sphere collision diameter; for b/l > 1.0, the probabilities decrease very rapidly with increasing b. The results show that nonzero-b collisions must be included in the calculation of simultaneous transition processes in H₂ + Ar at higher collision velocities.