Quantum dynamics of the C(D1)+HD and C(D1)+n−D2 reactions on the ã A1′ and b̃ A1″ surfaces

Feshbach resonances in D + HD(v = 1, j = 0) reaction at low collision energies

Feshbach resonances in D + HD(v = 1, j = 0) reaction are studied by using the time-independent quantum method. The integral cross section (ICS) results present three Feshbach resonance peaks, which are different from H + HD(v = 1, j = 0) reaction dominated by only one peak. These resonances are attributed to coupling with adiabatic effective potentials of D + HD(v = 1, j = 1) reaction, and the most obvious peak is contributed by J = 1 at 83.16 cm^-1 collision energy. For J = 0 and 2, the resonances are related with the same L partial wave and present a double-peak structure in total ICS. The characteristics of product angular distribution show that the resonance of J = 1 is long-lived, while the lifetimes are relatively shorter for the resonance of J = 0 and 2.

Dynamics study on the non-adiabatic Na(3p) + HD → NaH/NaD + D/H reaction: insertion-abstraction mechanism

Time-dependent wave packet calculations are carried out for two reaction channels of the non-adiabatic Na(3p) + HD → NaH/NaD + D/H reaction. The potential well on the excited state potential energy surface makes the reaction preferable to proceed through the insertion reaction path. The dominance of the NaD + H reaction channel and product rotational state distributions are found to be in agreement with the characteristics of typical adiabatic insertion reactions. However, significant forward scattering peaks in the differential cross sections (DCS) are found to be inconsistent with the forward-backward symmetric scattering characteristic of typical adiabatic insertion reactions, which indicate that the Na(3p) + HD reaction is dominated by a direct reaction mechanism. The comparison between adiabatic and non-adiabatic calculated DCSs reveals that the non-adiabatic couplings in the reaction could reduce the lifetime of the intermediate complex. Finally, the insertion-abstraction mechanism is put forward for the non-adiabatic Na(3p) + HD reaction.

Quantum Dynamics Study of the C(1D) + HD Reaction on the ã1A' and b̃1A″ Potential Energy Surfaces

We present an in-depth theoretical study of the C(¹D) + HD (v = 0, j = 0) → CD (CH) (v', j') + H (D) reaction using a time-dependent wave packet method with full Coriolis coupling on the Zhang-Ma-Bian potential energy surfaces (PESs) recently constructed by our group. The integral cross sections (ICS), differential cross sections, CD/CH branching ratios, and product state distributions are calculated over a wide range of collision energies. We find that the vibrational branching ratio defined as ICS(v'=1)/ICS(v'=0) obtained from the b̃¹A″ PES is much smaller than that from the ã¹A' PES for both product channels, which may be attributed to the dynamical effects of the conical intersection regulated (CI-R) intermediate on the b̃¹A″ PES. The collision energy dependence of CD/CH branching ratios displays oscillatory structures, which may be caused by the resonance states supported by the wells on the PESs. The high-temperature rate coefficients are also obtained and compared with previous results. The role of the excited-state PESs is also discussed.

Reactive, Inelastic, and Dissociation Processes in Collisions of Atomic Oxygen with Molecular Nitrogen

We report the results of detailed calculations of reactive, inelastic, and dissociative processes in collisions of atomic oxygen with molecular nitrogen in their respective electronic ground states. Cross sections are calculated as a function of collision energy in the range 0.001-10 eV, considering the whole rovibrational ladder. Some problems related to the vibrational energy levels of the asymptotes of ³A″ and ³A' potential energy surfaces used in this work are solved by an appropriate scaling at the level of cross sections. The results are compared with data in the literature, obtaining excellent agreement with experimental thermal data for reactive processes on a very large temperature range, and reasonable agreement with indirect dissociative data. Significant discrepancies are observed with previous reactive state-to-state results calculated on less detailed potential energy surfaces. Inelastic results are compatible with extrapolation of experimental thermal rate coefficient for temperatures higher than 4500 K but completely fail to reproduce experimental data at room temperature. The issue is discussed, indicating the reasons and possible solutions to the problem, and a resonable rate coefficient is obtained combining experimental and theoretical results in the range 300-20000 K. Complete, accurate fits are provided for both reactive and dissociative state-to-state rate coefficients to use them in applicative numerical codes concerning air kinetics.

Quasiclassical trajectory study of the C(1D) + HD reaction

Isotopic branching ratios are investigated by detailed quasiclassical trajectory calculations on our recent singlet ground and excited potential energy surfaces.

An experimental and theoretical investigation of the C(1D) + D2 reaction

Rate constants derived from ring polymer molecular dynamics calculations confirm the validity of this method for studying low-temperature complex-forming reactions

Global analytical ab initio ground-state potential energy surface for the C((1)D)+H2 reactive system

A new global ab initio potential energy surface (called ZMB-a) for the 1(1)A' state of the C((1)D)+H2 reactive system has been constructed. This is based upon ab initio calculations using the internally contracted multireference configuration interaction approach with the aug-cc-pVQZ basis set, performed at about 6300 symmetry unique geometries. Accurate analytical fits are generated using many-body expansions with the permutationally invariant polynomials, except that the fit of the deep well region is taken from our previous fit. The ZMB-a surface is unique in the accurate description of the regions around conical intersections (CIs) and of van der Waals (vdW) interactions. The CIs between the 1(1)A' and 2(1)A' states cause two kinds of barriers on the ZMB-a surface: one is in the linear H-CH dissociation direction with a barrier height of 9.07 kcal/mol, which is much higher than those on the surfaces reported before; the other is in the C((1)D) collinearly attacking H2 direction with a barrier height of 12.39 kcal/mol. The ZMB-a surface basically reproduces our ab initio calculations in the vdW interaction regions, and supports a linear C-HH vdW complex in the entrance channel, and two vdW complexes in the exit channel, at linear CH-H and HC-H geometries, respectively.

Quantum wave packet and quasiclassical trajectory studies of the reaction H(2S) + CH(X2 Π; v = 0, j = 1) → C(1D) + H2 (X1 Σg+): 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 (1)A' 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(θr ), P(ϕr ), P(θr ,ϕr ), and the polarization-dependent generalized differential cross sections have been explored in detail by QCT approach.

Resonances in the Ne + H2(+) → NeH(+) + H proton-transfer reaction

We investigated the oscillations found in the integral cross section of the title reaction, which are particularly evident for Ne + H2(+)(v0 = 2,j0 = 1) [essentially isoenergetic with NeH(+)(v' = 0,j' = 0) + H] at low collision energy (Ecol < 0.30 eV). We employed mainly an exact time-independent (TI) quantum dynamics method and used the best potential energy surface available. From analysis of TI initial state selected to all integral cross sections, state-to-state integral cross sections, and the corresponding differential cross sections (DCSs), we showed that the oscillations correspond to resonances. They arise from the influence of the global [Ne-H-H](+) (collinear) minimum on dynamics and probably correspond to Feshbach resonances. Besides, the forward-backward peaking DCS (which oscillates with Ecol) behavior observed could be a signature for this type of resonances. Finally, as most data on resonances in bimolecular reactions correspond to neutral systems, we hope that the present results will encourage experimentalists to re-examine this benchmark system.