Quantum wave packet study of N(2D) + H2 reactive scattering

N(²D) + H₂ → NH + H reaction at zero total angular momentum is studied by using a time dependent quantum wave packet method. State‐to‐state and state‐to‐all reactive scattering probabilities for a broad range of energy are calculated. The probabilities show many sharp peaks that ascribed to reactive scattering resonances. The probabilities for J > 0 are estimated by using the J‐shifting method. The integral cross sections and thermal rate constants are then calculated. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Real wave packet and flux analysis studies of the H + F2 → HF + F reaction

The H + F₂ → HF + F reaction on ground state potential energy surface is investigated using the quantum mechanical real wave packet and Flux analysis method based on centrifugal sudden approximation. The initial state selected reaction probabilities for total angular momentum J = 0 have been calculated by both methods while the probabilities for J > 0 have been calculated by Flux analysis method. The initial state selected reaction probabilities, integral cross sections and rate coefficients have been calculated for a broad range of collision energy. The results show a large rotational enhancement of the reaction probability. Some resonances were seen in the state‐to‐state reaction probabilities while state‐to‐all reaction probabilities and the reaction cross section do not manifest any oscillations and the initial state selected reaction rate constants are sensitive to the temperature. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Quantum wave packet calculation of reaction probabilities,cross sections,and rate constants for the C(1D) + HD reaction

The time‐dependent real wave packet method has been used to study the C(¹D) + HD reaction. The state‐to‐state and state‐to‐all reactive scattering probabilities for a broad range of energies are calculated at zero total angular momentum. The probabilities for J > 0 are estimated from accurately computed J = 0 probabilities by using the J‐shifting approximation. The integral cross sections for a large energy range, and thermal rate constants are calculated. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Investigation of the molecular chemiluminescence SrCl(A2Π1/2,3/2, B2Σ+ → X2Σ+) and the atomic resonance fluorescence Sr(53P1 → 51S0) in the time-domain following the pulsed dye laser generation of Sr(53 PJ) in the presence of CH2Cl2

Time-resolved investigations of the atomic resonance fluorescence Sr(5³P₁ → 5¹S₀) and the molecular chemiluminescence from SrCl(A²Π_1/2,3/2, B²Σ⁺ → X²Σ⁺) are reported following the reaction of the electronically excited strontium atom, Sr(5s5p(³P_J)), 1.807 eV above its 5s²(¹S₀) electronic ground state, with CH₂Cl₂. The optically metastable strontium atom was generated by pulsed dye-laser excitation of ground state strontium vapor to the Sr(5³P₁) state at λ = 689.3 nm (Sr(5³P₁ ← 5¹S₀)) at elevated temperature (850 K) in the presence of excess helium buffer gas in which rapid Boltzmann equilibration within the 5³P_J manifold takes place. Sr(5³P_J) was then monitored by time-resolved atomic fluorescence from Sr(5³P₁) at the resonance wavelength together with chemiluminescence from electronically excited SrCl resulting from reaction of the excited atom with CH₂Cl₂. The molecular systems recorded in the time-domain were SrCl(A²Π_1/2 → X²Σ⁺) (Δν = 0, λ = 674 nm), SrCl(A²Π_3/2 → X²Σ⁺) (Δν = 0, λ = 660 nm), and SrCl(B²Σ⁺ → X²Σ⁺) (Δν = 0, λ = 636 nm). Both the A²Π (179.0 kJ mol^?1) and (B²Σ⁺(188.0) kJ mol^?1) states of SrCl are energetically accessible on collision between Sr(³P) and CH₂Cl₂. Exponential decay profiles for both the atomic and molecular (A,B – X) chemiluminescence emission are observed and the first-order decay coefficients characterized in each case. These are found to be equal under identical conditions and hence SrCl(A²Π, B²Σ⁺) are shown to arise from direct Cl-atom abstractions on reaction with this halogenated species. The combination of integrated molecular and atomic intensity measurements, coupled with optical sensitivity calibration, yields estimations of the branching ratios into the A_1/2,3/2, B, and X states arising from Sr(5³ P_J) + CH₂Cl₂ which are found to be as follows: A_1/2, 3.0 × 10^?3; A_3/2, 1.7 × 10^?3; B, 4.4 × 10^?4 yielding ΣSrCl(A_1/2 + A_3/2 + B) = 5.1 × 10^?3. As only the X, A and B states of SrCl are accessible on reaction, this indicates an upper limit for the branching ratio into the ground state of 0.995. The present results are compared with previous time-resolved measurements on SrF, Cl, Br(A²Π,B²Σ⁺ ? X²Σ⁺) that we have reported on various halogenated species and with analogous chemiluminescence studies on Sr(³P) with other halides obtained from molecular beam measurements. The results are further compared with those from a series of previous analogous investigations in the time-domain we have presented of molecular emissions from CaF, Cl, Br, I (A,B – X) arising from the collisions of Ca(4³P_J) with appropriate halides and with branching ratio data for Ca(4³P_J) obtained in beam measurements. © 1995 John Wiley & Sons, Inc.     

Quantum wave packet calculation of reaction probabilities,cross sections,and rate constants for H+ + LiH → Li + H reaction

The H⁺ + LiH → Li + H reactive scattering has been studied using a quantum real wave packet method. The state‐to‐state and state‐to‐all reaction probabilities for the entitled collision have been calculated at zero total angular momentum. The probabilities for J > 0 are estimated from the J = 0 results by using J‐shifting approximation based on the Capture model. The integral cross sections and thermal rate constants are then calculated. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Dynamical properties of S(3P) + HD reaction on 13A″state and their quantum wavepacket calculation

The time‐dependent wavepacket method is used to study the reaction dynamics of S(³P) + HD (v = 0, 1, 2) on the adiabatic 1³A″ potential energy surface constructed by Han and coworkers [J. Chem. Phys. 2012, 136, 094308]. The reaction probabilities and integral cross sections as a function of collision energy are obtained and discussed. The results calculated by using the CC and the CS approximation have been compared, which suggests that for this direct abstraction reaction, the cheaper CS approximation calculation is valid enough in the quantum calculation. The investigation also shows that the reaction probabilities and integral cross sections tend to increase with collision energy. By analyzing the v‐dependent behavior of the integral cross sections, the significant effect of the vibrational excitation of HD is found. Also found in the calculation is a significant resonance feature in the reaction probabilities versus collision energy. © 2014 Wiley Periodicals, Inc.     

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.     

On a simple reaction mechanism for the collision-induced dissociation He + Li2(B1Πu) → He + Li(2 2S) + Li(2 2P)

A simple reaction mechanism is suggested for the dissociation of electronically excited Li₂(B¹Π_u) in collision with rare-gas atoms. Experimental rate constants for dissociation of Li₂ in specific vibrational—rotational levels (ν1J) show an unexpected behaviour as a function of the initial molecular energy and angular momentum. We propose that raction proceeds by a transition to the ¹Π_g state of Li₂. This may dissociate more readily since it is more weakly bound and has a larger equilibrium distance than the ¹Π_u state.     

Direct ab initio dynamics study of the reaction of C2(A3Πu) with CH4

The reaction of C₂(A³Π_u) with CH₄ has been investigated over a wide temperature range 200–3,000 K by direct ab initio dynamics method at the BMC‐CCSD//BB1K/6‐311+G(2d,2p) level of theory. The optimized geometries and frequencies of the stationary points are calculated at the BB1K/6‐311+G(2d,2p) level, and then the energy profiles of the reactions are refined using the BMC‐CCSD method. The activation barrier height for H‐abstraction reaction was calculated to be 4.44 kcal/mol in temperature range (337–605 K), and the electron transfer behavior was also analyzed by quasi‐restricted molecular orbital method in detail. The canonical variational transition‐state theory (CVT) with the small curvature tunneling (SCT) correction method is used to calculate the rate constants over a wide temperature range 200–3,000 K. The theoretical results shows that variational effect is to some extent large in lower temperature range, and small curvature and tunneling effect play important roles to the H‐atom abstraction only at lower temperatures. The CVT/SCT rate constants are in good agreement with the available experimental results. Our theoretical study is expected to provide a direct insight into the reaction mechanism and may be useful for estimating the kinetics of the title reaction over a wide temperature range where no experimental data are available so far. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Yields of O2(1Σg+) and O2(1Δg) in the H + O2 reaction system,and the quenching of O2(1Σg+) by atomic hydrogen

The generation of metastable O₂(¹Σg⁺) and O₂(¹Δg) in the H + O₂ system of reactions was studied by the flow discharge chemiluminescence detection method. In addition to the O₂(¹Σg⁺) and O₂(¹Δg) emissions, strong OH(v = 2) → OH(v = 0), OH(v = 3) → OH(v = 1), HO₂(²A′₀₀₀) → HO₂(²A″₀₀₀), HO₂(²A′₀₀₁) → HO₂(²A″₀₀₀), and H O₂(²A″₂₀₀) → HO₂(²A″₀₀₀) emissions were detected in the H + O₂ system. The rate constants for the quenching of O₂(¹Σg⁺) by H and H₂ were determined to be (5.1 ± 1.4) × 10^?13 and (7.1 ± 0.1) × 10^?13 cm³ s^?1, respectively. An upper limit for the branching ratio to produce O₂(¹Σg⁺) by the H + HO₂ reaction was calculated to be 2.1%. The contributions from other reactions producing singlet oxygen were investigated.     

The N(4S) + N2O(X̃1∑) reaction

The title reaction, which is spin‐forbidden for N₂(X¹∑) + NO(X²Π) production, has been studied from 960 to 1130 K in a high‐temperature photochemistry reactor. No reaction could be observed, indicating k < 1 × 10^?15 cm³ molecule^?1 s^?1. It is concluded that there is no significant contribution from the spin‐allowed exothermic path leading to N₂(X¹∑) + NO(a⁴Π). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 387–389, 2001     

A comparison of attack angle dependence of exchange channel of reaction H + HS (v = 0, 1; j = 0) on 3A″ and 3A′ surfaces

In this theoretical work, we report quasiclassical dynamics predictions for the attack angle‐dependence exchange processes for the H + HS (v = 0, 1; j = 0) reaction by using the new triplet 3A″ and 3A′ potential energy surfaces, respectively. The calculated quasiclassical reaction probabilities of exchange reaction channel of reaction H(D)′ + H(D)S for J = 0, 10, 20, 30, 40 are in good agreement with quantum wave packet results over the collision energy range from 0.1 to 2.0 eV on 3A″ surfaces. The attack angle dependence reaction probability of the title reactions at J = 0 are calculated, respectively, on the two surfaces. The reaction probability was found to be strongly dependent on the attack angle. It may be ascribe to the significant difference of the effective potential barrier height in the two reactions. Besides, the reaction probabilities of exchange reaction channel of reaction H(D)′ + H(D)S for J = 0, 10, 20, 30, 40 are also predicted on 3A′ surfaces. © 2013 Wiley Periodicals, Inc.     

Quantum wave packet and quasiclassical trajectory studies of the reaction H(2S) + CH(X2Π; v = 0, j = 1) → C(1D) + H2(X1 ): Coriolis coupling effects and stereodynamics

The quantum mechanics (QM) and quasiclassical trajectory (QCT) calculations have been carried out for the title reaction with the ground minimal allowed rotational state of CH (j = 1) on the 1 ¹A′ potential energy surface. For the reaction probability at total angular momentum J = 0, a similar trend of the QM and QCT calculations is observed, and the QM results are larger than the latter almost in the whole considered energy range (0.1–1.5 eV). The QCT integral cross sections are larger than the QM results with centrifugal sudden approximation, while smaller than those from QM method including Coriolis coupling for collision energies bigger than 0.25 eV. The quantum wave‐packet computations show that the Coriolis coupling effects get more and more pronounced with increasing of J. In addition to the scalar properties, the stereodynamical properties, such as the average rotational alignment factor <P₂( j′?k )>, the angular distributions P(θ_r), P(?_r), P(θ_r,?_r), and the polarization‐dependent generalized differential cross sections have been explored in detail by QCT approach. © 2013 Wiley Periodicals, Inc.     

Exploring the reaction dynamics of O(3P)+ (X2 )→OH+(X3Σ−)+ H(2S) reaction with time‐dependent wave packet method

The O(³P)+ reaction has been investigated by employing time‐dependent quantum wave packet with split operator method on potential energy surface of the doublet ground‐state H₂O⁺(1²A″). The reaction probabilities and integral cross sections are calculated using centrifugal sudden approximation, which basically agree with the quasi‐classical results of Paniagua et al. [Phys. Chem. Chem. Phys. 2014, 16, 23594]. Moreover, the effect of vibrational and rotational excitation of reactant is investigated. The results show that the vibrational and rotational excitation effects on the integral cross section are not obvious. The little differences between Coriolis coupling results and centrifugal sudden approximation ones show that the cheaper centrifugal sudden calculations here reported are effective for this reaction.     

Classical dynamics of the O + ClO → Cl + O2 and Cl + O3 → ClO + O2 reactions

An explicit function has been derived for the potential-energy surface of the ground state of ClO₃ with the six interatomic distances as variables. This surface is valid over all configurations of the atoms. The surface has been used to calculate classical trajectories for the reactions R₁: O(³P₂)+ClO(²Π_3/2)→ O₂(³∑)+Cl(²)P_3/2 and R₂: Cl(²P_3/2)+O₃(¹A₁)→ClO(²Π_3/2)+O₂(³∑). An appreciable fraction (～1/3) of the reactive trajectories for R₁ go through a long-lived complex ClOO(²A″). The cross section decreases with increasing rotational state of the ClO; and 37% of the energy release is vibrational. The calculated rate constant at 298°K is 2.6 × 10^?11 cm³/molecule sec. For reaction R₂ there is no evidence of long-lived complexes. The product ClO is predominantly found in the backward-scattering direction. Most of the internal energy is carries off by ClO but O₂ carried off most translational energy. An Arrhenius expression has been deduced from calculations at 220 and 300°K to give an A factor of 2.488 × 10^?11 cm³/molecule sec and an activation energy of 1.543 kJ/mol.     

Quantum reaction dynamics of C(1D) + HD → CH(CD) + D(H) on the ground state potential energy surface

We present accurate quantum dynamic calculations of the reaction C(¹D) + HD on the latest version of the potential energy surface [Zhang et al., J. Chem. Phys. 140, 234301 (2014)]. Using a Chebyshev real wave packet method with full Coriolis coupling, we obtain the initial state‐specified ( ) reaction probabilities, integral cross sections, and rate constants. The resulting probabilities display oscillatory structures due to numerous long‐lived resonances supported by the deep potential well. The calculated rate constants and CD/CH product branching ratio at room temperature are in reasonably good agreement with the experimental measurements.     

Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1- (3′-O-Phosphoryl-2′-deoxy-β -D-ribofuranosyl)-2(1H)-pyridone-(3′-5′)-1-(2′-deoxy-β-D-ribofuranosyl)-2 (1H)-pyridone

The dinucleoside phosphate Π_dpΠ_d ( 4 ) was synthesized from the monomers 1-(5′-O-monomethoxytrityl - 2′ - deoxy - β - D - ribofuranosyl) - 2 (1 H) - pyridone ((MeOTr) Π_d, 2 ) and 1-(5′-O-phosphoryl-3′-O-acetyl-2′-deoxy-β-D -ribofuranosyl)-(1H)-pyridone (pΠ_d(Ac), 3 ). Its 6.4% hyperchromicity and an analysis of the ¹H-NMR. spectra indicate that the conformation and the base-base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.     

Theoretical investigations on analytical potential energy function and spectroscopic parameters for the state b3Πu of dimer 7Li2

The SAC‐CI (symmetry‐adapted‐cluster configuration‐interaction) method presented in Gaussian 03 program package is applied to investigate the adiabatic potential energy curves (PECs) of ⁷Li₂(b³Π_u). These calculations are performed at numbers of basis sets, such as 6‐311++G(3df,3pd), 6‐311++G(2df,2pd), 6‐311++G(df,pd), D95V++, D95(3df,3pd), D95(d,p), cc‐PVTZ, 6‐311++G and 6‐311++G(d,p). All the ab initio calculated points are fitted to the analytic Murrell‐Sorbie functions and then used to compute the spectroscopic parameters. The analytic potential energy function (APEF) for this b³Π_u state is reported. By comparison, the spectroscopic parameters reproduced by the APEF attained at 6‐311++G(2df,2pd) are found to be very close to the latest experimental findings. With the APEF obtained at the SAC‐CI/6‐311++G(2df,2pd) level of theory, a total of 62 vibrational states is found when J = 0. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants for these vibrational states are also reported. The reasonable dissociation limit for this state is deduced using the calculated results at present. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Time-dependent quantum study of the kinetics of the H(2S) + FO(2II) OH(2II) + F(2P) reaction

Quantum mechanical wave packet calculations are carried out for the H((2)S) + FO((2)II) --> OH((2)II) + F((2)P) reaction on the adiabatic potential energy surface of the ground (3)A' triplet state. The state-to-state and state-to-all reaction probabilities for total angular momentum J = 0 have been calculated. The probabilities for J > 0 have been estimated from the J = 0 results by using J-shifting approximation based on a capture model. Then, the integral cross sections and initial state-selected rate constants have been calculated. The calculations show that the initial state-selected reaction probabilities are dominated by many sharp peaks. The reaction cross section does not manifest any sharp oscillations and the initial state-selected rate constants are sensitive to the temperature.     

Theoretical study of the mechanism for spin‐forbidden quenching process O(1D) + CO2(1Σ) → O(3P) + CO2(1Σ)

The mechanism of the spin‐forbidden quenching process O(¹D) + CO₂(¹Σ) → O(³P) + CO₂(¹Σ) was investigated by ab initio quantum chemistry methods. The calculations showed the singlet potential surface [O(¹D)+CO₂] is attractive where a strongly bound intermediate complex CO₃ is formed in the potential basin without a transition state, whereas the complex CO₃ that is formed on the triplet surface [O(³P)+CO₃] must overcome a barrier. The complex channel was documented by searching minimum energy intersection points in the region of the bound complex CO₃ and calculating spin‐orbit coupling at the point. A direct channel was proposed by a study of cross point of singlet and triplet PESs with different collision angles and calculations of spin‐orbit coupling at those cross points in a nonbound region of the [O(¹D)+CO₃] system. The mechanism of the energy transfer is discussed on the basis of the theoretical results. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005