Seemingly Anomalous Angular Distributions in H + D2 Reactive Scattering

Science ◽  
2012 ◽  
Vol 336 (6089) ◽  
pp. 1687-1690 ◽  
Author(s):  
Justin Jankunas ◽  
Richard N. Zare ◽  
Foudhil Bouakline ◽  
Stuart C. Althorpe ◽  
Diego Herráez-Aguilar ◽  
...  
Keyword(s):  
Cross Sections ◽  
Collision Energy ◽  
Minimum Energy ◽  
Angular Distributions ◽  
Quantum Mechanical ◽  
Minimum Energy Path ◽  
Reactive Scattering ◽  
Rotational Excitation ◽  
Reaction Products ◽  
Trajectory Calculations

When a hydrogen (H) atom approaches a deuterium (D2) molecule, the minimum-energy path is for the three nuclei to line up. Consequently, nearly collinear collisions cause HD reaction products to be backscattered with low rotational excitation, whereas more glancing collisions yield sideways-scattered HD products with higher rotational excitation. Here we report that measured cross sections for the H + D2 → HD(v′ = 4, j′) + D reaction at a collision energy of 1.97 electron volts contradict this behavior. The anomalous angular distributions match closely fully quantum mechanical calculations, and for the most part quasiclassical trajectory calculations. As the energy available in product recoil is reduced, a rotational barrier to reaction cuts off contributions from glancing collisions, causing high-j′ HD products to become backward scattered.

Theoretical investigations of the Au++H2 reactive scattering by the time-dependent quantum wave packet method

2017 ◽  
Vol 31 (06) ◽  
pp. 1750039 ◽  
Author(s):  
Wentao Lee ◽  
Haixiang He ◽  
Maodu Chen
Keyword(s):  
Wave Packet ◽  
Cross Sections ◽  
Collision Energy ◽  
Time Dependent ◽  
Reactive Scattering ◽  
Total Reaction ◽  
Theoretical Investigations ◽  
Classical Trajectories ◽  
Quantum Wave

Employing the state-to-state time-dependent quantum wave packet method, the Au[Formula: see text]H2 reactive scattering with initial states [Formula: see text], [Formula: see text] and 1 were investigated. Total reaction probabilities, product state-resolved integral cross-sections (ICSs) and differential cross-sections (DCSs) were calculated up to collision energy of 4.5 eV. The numerical results show that total reaction probabilities and ICSs increase with increasing collision energies, and there is little effect to the reactive scattering processes from the rotational excitation of H2 molecule. Below collision energy of around 3.0 eV, the role of the potential well in the entrance channel is significant and the reactive scattering proceeds dominantly by an indirect process, which leads to a nearly symmetric shape of the DCSs. With collision energy higher than 4.0 eV, the reactive scattering proceeds through a direct process, which leads to a forward biased DCSs, and also a hotter rotational distributions of the products. Total ICS agrees with the results by the quasi-classical trajectories theory very well, which suggests that the quantum effects in this reactive process are not obvious. However, the agreement between the experimental total cross-section and our theoretical result is not so good. This may be due to the uncertainty of the experiment or/and the inaccuracy of the potential energy surface.

Reagent vibrational, rotational and isotopic effects on stereodynamics of the H + OCl → OH + Cl reaction

2014 ◽  
Vol 13 (01) ◽  
pp. 1450002
Author(s):  
Ruifeng Lu ◽  
Zhenyu Xu ◽  
Yunhui Wang
Keyword(s):  
Cross Sections ◽  
Collision Energy ◽  
Energy Surface ◽  
Vibrational Excitation ◽  
Classical Trajectory ◽  
Angular Distributions ◽  
Title Reaction ◽  
Generalized Polarization ◽  
Trajectory Method ◽  
Isotopic Effects

The quasi-classical trajectory method has been employed to investigate the initial vibrational and rotational effects of the title reaction on an improved ab initio potential energy surface for the 11A′ state. Meanwhile, isotopic effect has also been studied at collision energy of 19 kcal/mol. The product rotational alignment factor 〈P2(j′ • k)〉, angular distributions of P(ϕr), P(θr) and the generalized polarization dependent differential cross-sections have been calculated. The- results show that the reagent vibrational excitation generally strengthens the product alignment perpendicular to the reagent relative velocity vector k and affects the product scattering preference, and the rotational excitation has the same trend from j = 0 to 2 except for the higher excitation of j = 3. Further, the substitution of atom H with D leads to a stronger product alignment while changes some stereodynamical properties subtly.

The dynamics of the Br + HgBr (v = 0, j = 0) → Br2 + Hg reaction based on quasi-classical trajectory calculations

2018 ◽  
Vol 96 (8) ◽  
pp. 926-932 ◽  
Author(s):  
Guan-Qing Ren ◽  
Ai-Ping Fu ◽  
Shu-Ping Yuan ◽  
Tian-Shu Chu
Keyword(s):  
Angular Momentum ◽  
Cross Sections ◽  
Relative Velocity ◽  
Total Angular Momentum ◽  
Collision Energy ◽  
Energy Surface ◽  
Classical Trajectory ◽  
Title Reaction ◽  
Trajectory Calculations ◽  
Angular Momentum Quantum Number

To investigate the dynamics mechanism of the Br + HgBr → Br2 + Hg reaction, the quasi-classical trajectory calculations are performed on Balabanov’s potential energy surface (PES) of ground electronic state. Both the scalar and vector properties are investigated to recognize the dynamics of the title reaction. Reaction probability for the total angular momentum quantum number J = 0 is determined at the collision energies (denoted as Ec) in a range of 1–25 kcal/mol, and the product vibrational distributions are given and compared between Ec = 20 and 40 kcal/mol. Other calculation values characterizing product polarizations including polarization-dependent differential cross sections (PDDCSs), distributions of P(θr), P([Formula: see text]), and P(θr, [Formula: see text]), are all discussed and compared between the two different collision energies in detail to analyze the alignment and orientation characteristics. It is revealed that the products prefer forward scattering and the PDDCSs are anisotropic in the whole range of the scattering angle. The product rotational angular momentum j′ shows a tendency to align perpendicular to the reagent relative velocity k. In fact, the product polarization of the title reaction is weak at both collision energies. In terms of horizontal comparison, the alignment is slightly stronger but the orientation is even less remarkable at higher collision energy.

EFFECTS OF ROTATIONAL AND VIBRATIONAL EXCITATION ON THE STEREODYNAMICS OF THE O (D-1) + HCl → OH + Cl REACTION

2009 ◽  
Vol 08 (06) ◽  
pp. 1177-1184 ◽  
Author(s):  
QIANG WEI ◽  
VICTOR WEI-KEH WU ◽  
BO ZHOU
Keyword(s):  
Cross Sections ◽  
Collision Energy ◽  
Energy Surface ◽  
Vibrational Excitation ◽  
Classical Trajectory ◽  
Rotational Excitation ◽  
Title Reaction ◽  
Vibrational Excitations ◽  
Product Vector ◽  
Good Agreement

The stereodynamics of the title reaction on the ground 1 1A′ potential energy surface (PES) has been studied using quasi-classical trajectory (QCT) method. Collision energy of 6.4 kcal/mol is considered, and vector properties including angular momentum alignment distributions and polarization-dependent differential cross-sections (PDDCS) of the product OH are presented. Furthermore, the influence of reagent rotational excitation and vibrational excitation on the product vector properties has also been studied in the present work. The results indicate that the distribution of the P(θr) and P(ϕr) are sensitively affected by the rotational and vibrational excitation. The rotational excitation decreases the degree of alignment and orientation, while vibrational excitation increases the degree of alignment and orientation. The PDDCS (2π/σ)(dσ20/dωt) and (2π/σ)(dσ22+/dωt) are sensitively influenced by rotational and vibrational excitations, while the PDDCS ((2π/σ)(dσ00/dωt)) and (2π/σ)(dσ21-/dωt) are not. The preference of forward scattering has been found from the results of PDDCS ((2π/σ)(dσ00/dωt)), which is in good agreement with the experimental results.

A quasi-classical trajectory (QCT) study of the H + OF reaction stereodynamics

2010 ◽  
Vol 88 (9) ◽  
pp. 893-897 ◽  
Author(s):  
Dan Zhao ◽  
Tian Yu Zhang ◽  
Tian Shu Chu
Keyword(s):  
Cross Sections ◽  
Relative Velocity ◽  
Collision Energy ◽  
Potential Surface ◽  
Excited Electronic State ◽  
Three Dimensional ◽  
Chem Phys ◽  
Classical Trajectory ◽  
Angular Distributions ◽  
Angular Momenta

Based on the global three-dimensional adiabatic potential surface of the 13A′ excited electronic state (J. Chem. Phys. 2005, 123, 114310) of the OHF system, we investigated the H + OF → OH + F/HF + O reaction stereodynamics by using the quasi-classical trajectory (QCT) method. The four polarization-dependent differential cross sections (PDDCSs) and the three angular distributions P(θr), P([Formula: see text]), P(θr, [Formula: see text]) were calculated at a low collision energy of 0.48 eV for both product channels. The results indicated that the products are backward-scattering on the triplet state, and the product rotational angular momenta are aligned or oriented. Moreover, there is a remarkable difference between the polarization behaviors of the two product channels. Product orientation exhibited by the OH + F channel is found to be absent in the HF + O channel at this collision energy albeit the latter shows stronger alignment along the direction perpendicular to the reagent relative velocity k than OH + F.

QUASICLASSICAL TRAJECTORY STUDY OF PRODUCT POLARIZATIONS IN THE H(2S) + NH → N(4S) + H2 REACTION

2012 ◽  
Vol 11 (06) ◽  
pp. 1297-1310 ◽  
Author(s):  
LIN LI ◽  
SHUNLE DONG
Keyword(s):  
Angular Momentum ◽  
Cross Sections ◽  
Differential Cross ◽  
Ground State ◽  
Calculation Method ◽  
Collision Energy ◽  
Potential Surface ◽  
Angular Distributions ◽  
Title Reaction ◽  
Energy Dependent

Based on the DMBE potential surface of the 4 A ″ ground-state, the product rotational polarizations in the title reaction are studied by using quasiclassical trajectory (QCT) calculation method. Three angular distributions of P(θr), P(Φr), P(θr, Φr) and the four polarization-dependent differential cross sections (PDDCSs) were calculated for the collision energy range of 1–20 kcal/mol. The results revealed that the product is backward-scattering and the product rotational angular momentum j′ is aligned and oriented. With the increment of collision energy, the degree of the product alignment and orientation is enhanced, showing the collision energy-dependent behaviors of the product polarizations.

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