Total Integral Cross Sections Research Articles

Theoretical study of S + SH reaction on its ground state HS2(X2 A ″) potential energy surface

ABSTRACT In this study, we explore the initial state selected dynamics of the S + SH ( X 2 Π ) → S 2 ( X 3 ∑ ) + H reaction through the lens of time-dependent quantum dynamics (QD), quasi-classical trajectory (QCT), and statistical quantum mechanical (SQM) approaches, utilising the electronic ground state HS 2 (X 2 A ′′ ) potential energy surface (PES). We present total reaction probabilities and integral cross sections (ICSs) as part of our findings. Our results indicate that at low and moderate collision energies, the reaction predominantly follows an indirect pathway, forming meta-stable quasi-bound complexes. Additionally, we observe that the rotational excitation of the SH reagent initially leads to a decrease and then an increase in reactivity. We conduct a comprehensive analysis and comparison of the outcomes from QD, QCT, and SQM methodologies.

Angular differential cross section measurement for 11B(p, α0)8Be reaction with proton energy of 2.5 MeV

This report presents experimental differential cross section measurements at α0-particles’ eight outgoing angles of 50°, 70°, 90°, 106°, 120°, 130°, 150°, and 160° from 11B(p, α0)8Be reaction induced by 2.5 MeV proton beam bombarding on a natural boron target. The proton beams were accelerated by the 5SDH-2 pelletron at the University of Science - Hanoi National University (HUS). A good agreement has been observed between the obtained results and those from the literature. The importance of the data in a widely angular range is evidenced for the precise determination of the total integrated cross section.

State-to-State Quantum Dynamics Study of Intramolecular Isotope Effects on Be(1S) + HD (v0 = 2, j0 = 0) → BeH/BeD + H/D Reaction.

The dynamic mechanisms and intramolecular isotope effects of the Be(1S) + HD (v0 = 2, j0 = 0) → BeH/BeD + H/D reaction are studied at the state-to-state level using the time-dependent wave packet method on a high-quality potential energy surface. This reaction can proceed along the indirect pathway that features a barrier and a deep well or the smooth direct pathway. The reaction probabilities, total and state-resolved integral cross sections, and differential cross sections are analyzed in detail. The calculated dynamics results show that both of the products are mainly formed by the dissociation of a collinear HBeD intermediate when the collision energy is slightly larger than the threshold. As the collision energy increases, the BeH + D channel is dominated by the direct abstraction process, whereas the BeD + H channel mainly follows the complex-forming mechanism.

Coupled 3D (J ≥ 0) Time-Dependent Wave Packet Calculation for the F + H2 Reaction on Accurate Ab Initio Multi-State Diabatic Potential Energy Surfaces.

We had calculated adiabatic potential energy surfaces (PESs), nonadiabatic, and spin-orbit (SO) coupling terms among the lowest three electronic states (12A', 22A', and 12A″) of the F + H2 system using the multireference configuration interaction (MRCI) level of theory, and the adiabatic-to-diabatic transformation equations were solved to formulate the diabatic Hamiltonian matrix [J. Chem. Phys. 2020, 153, 174301] for the entire region of the nuclear configuration space. The accuracy of such diabatic PESs is explored by performing scattering calculations to evaluate integral cross sections (ICSs) and rate constants. The nonadiabatic and SO effects are studied by utilizing coupled 3D time-dependent wave packet formalism with zero and nonzero total angular momentum on multiple adiabatic/diabatic surfaces calculation. We depict the convergence profiles of reaction probabilities for the reactive as well as nonreactive processes on various electronic states at different collision energies with respect to total angular momentum including all helicity quantum numbers. Finally, total ICSs are calculated as functions of collision energies for the initial rovibrational state (v = 0, j = 0) of the H2 molecule along with the temperature-dependent rate coefficient, where those quantities are compared with previous theoretical and experimental results.

Dynamical studies for the S+ + D2(v0 = 2, j0 = 0) → SD+ + D reaction by time-dependent wave packet

Using time-dependent wave packet method, the dynamics studies of the S+ + D2(v0 = 2, j0 = 0) → SD+ + D reaction were carried out based on the potential energy surface (PES) reported by Zhu et al., (Phys. Chem. Chem. Phys.23 4757–4767 (2021)). The isotope effect is very obvious. When the H atom is replaced by the D atom, the reaction probability at total angular momentum equal to zero has a threshold of about 0.28 eV and it decreases significantly in the collision energy range studied. The total and rovibrational state-resolved integral cross section were reported and the results indicate that the distribution of integral cross section is mainly concentrated in the ground state. The forward biased differential cross sections show that the stripping mechanism due to high total angular momentum plays a dominant role in the reaction.

Multireference configuration interaction study of the predissociation of C2 via its F1Πu state.

Photodissociation is one of the main destruction pathways for dicarbon (C2) in astronomical environments, such as diffuse interstellar clouds, yet the accuracy of modern astrochemical models is limited by a lack of accurate photodissociation cross sections in the vacuum ultraviolet range. C2 features a strong predissociative F1Πu-X1Σg + electronic transition near 130nm originally measured in 1969; however, no experimental studies of this transition have been carried out since, and theoretical studies of the F1Πu state are limited. In this work, potential energy curves of excited electronic states of C2 are calculated with the aim of describing the predissociative nature of the F1Πu state and providing new ab initio photodissociation cross sections for astrochemical applications. Accurate electronic calculations of 56 singlet, triplet, and quintet states are carried out at the DW-SA-CASSCF/MRCI+Q level of theory with a CAS(8,12) active space and the aug-cc-pV5Z basis set augmented with additional diffuse functions. Photodissociation cross sections arising from the vibronic ground state to the F1Πu state are calculated by a coupled-channel model. The total integrated cross section through the F1Πu v = 0 and v = 1 bands is 1.198 × 10-13 cm2 cm-1, giving rise to a photodissociation rate of 5.02 × 10-10 s-1 under the standard interstellar radiation field, much larger than the rate in the Leiden photodissociation database. In addition, we report a new 21Σu + state that should be detectable via a strong 21Σu +-X1Σg + band around 116nm.

Accurate Calculation of Rate Constant and Isotope Effect for the F + H2 Reaction by the Coupled 3D Time-Dependent Wave Packet Method on the Newly Constructed Ab Initio Ground Potential Energy Surface.

We employ coupled three-dimensional (3D) time dependent wave packet formalism in hyperspherical coordinates for reactive scattering problem on the newly constructed ab initio calculated ground adiabatic potential energy surface for the F + H2/D2 reaction. The convergence profiles for various reactive channels are depicted at low collision energy regimes with respect to the total angular momentum (J) quantum numbers. For two different reactant diatomic molecules (H2 and D2) initially at their respective ground roto-vibrational state (v = 0, j = 0), calculated state-to-state as well as total integral cross sections as a function of collision energy, temperature dependent rate constants, and the kinetic isotope effect for various reactivity profiles of F + H2 and F + D2 reactions are presented along with previous theoretical and experimental results.

Coherent multichannel optical theorem: Quantum control of the total scattering cross section

The optical theorem is a fundamental aspect of quantum scattering theory. Here, we generalize this theorem to the case where the incident scattering state is a superposition of internal states of the collision partners, introducing additional interference contributions and, e.g., providing a route to control the total integral cross section. As in its standard form, forward scattering plays an essential role in the multichannel optical theorem, but with interference terms being related to the inelastic forward scattering amplitudes between states in the initial superposition. Using the resultant control index, we show that extensive control is possible over ultracold collisions of oxygen molecules in their rovibrational ground states, and of $^{85}\mathrm{Rb}\text{\ensuremath{-}}^{85}\mathrm{Rb}$ collisions, promising systems for the experimental demonstration of the quantum interference control of the total scattering cross section.

Time-dependent wave packet dynamics study of the resonances in the H + LiH+(v = 0, j = 0) → Li+ + H2 reaction at low collision energies.

The depletion process of LiH+ by H collision plays an important role in the evolution of the early universe and astrophysical processes, including the eventual charge-states, abundances of atomic and molecular species and ensuing astrochemistry. Here, a quantum dynamics study on the H + LiH+(v = 0, j = 0) → Li+ + H2 reaction is performed at the low collision energy range from 0.1 meV to 10 meV using the time-dependent wave packet method. A Feshbach resonance peak is observed near 0.8 meV collision energy on the total reaction probability curves. This resonance originates from the coupling with the v = 0, j = 1 energy level of the reactant LiH+, and it is dominated by the contributions of J = 0-4 partial waves. Another partial wave resonance is also found on the total integral cross section at 1.2 meV, which is closely connected to the opening of the J = 7 partial wave. The opening of the J = 7 partial wave generates a notable forward scattering peak, and the Feshbach resonance can promote both the forward and backward scatterings. Moreover, the total and product vibrational state-resolved rate coefficients for the temperature range of 1-100 K are also reported.

Kinetics and dynamics of the H(2S) + NO(X2Π) → N(4S) + OH(X2Π) reaction: A quasi-classical trajectory study

A quasi-classical trajectory study of the H(2S) + NO(X2Π) → N(4S) + OH(X2Π) reaction kinetics and dynamics is reported on an accurate potential energy surface. The total integral cross sections of the reaction were calculated at the collision energy ranging from 2.00 eV to 2.80 eV. It was found that the total reaction integral cross section increases monotonically with the collision energy. Specifically at the collision energy range of 2.40–2.57 eV, our calculated results are in reasonably good agreement with the experimental data. The calculated thermal rate constants are in fairly good agreement with available experimental results. Through the trajectory analysis at the collision energy of 2.57 eV, it was found that the title reaction is dominated by the indirect trajectories (1.4 times more compared to the direct trajectories), which sheds light on the reaction dynamics of the title reaction in the high collision energy range.

Molecular beam scattering experiments on noble gas-propylene oxide: Total integral cross sections and potential energy surfaces of He- and Ne-C3H6O.

The interactions of He and Ne with propylene oxide have been investigated with the molecular beam technique by measuring the total (elastic + inelastic) integral cross section as a function of collision velocity. Starting from the analysis of these experimental data, potential energy surfaces, formulated as a function of the separation distance and orientation of propylene oxide with respect to the interacting partners, have been built: The average depth of potential wells (located at intermediate separation distances) has been characterized by analyzing the observed "glory" quantum effects, and the strength of long-range attractions has been obtained from the magnitude and the velocity dependence of the smooth component of measured cross sections. The surfaces, tested and improved against new ab initio calculations of minima interaction energies at the complete basis set level of theory, are defined in the full space of relative configurations. This represents a crucial condition to provide force fields useful to carry out, in general, important molecular property simulations and to evaluate, in the present case, the spectroscopic features and the dynamical selectivity of weakly bound complexes formed by propylene oxide, a prototype chiral species, during collisions in interstellar clouds and winds, in the space and planetary atmospheres. The adopted formulation of the interaction can be readily extended to similar systems, involving heavier noble gases or diatomic molecules (H2, O2, and N2) as well as to propylene oxide dimers.

Dynamic study of the D + DAu reaction based on a new ground potential energy surface

Based on the ground potential energy surface (PES) (2A') constructed by Yuan and coworkers, the D + DAu reactive scattering was investigated using the time-dependent wave packet method. It was found that the total reaction probabilities and integral cross section of the D + DAu reaction are smaller than those of the H + HAu reaction, due to smaller zero point energy and weaker tunneling effect. The abstract and exchange reaction channel exhibit different reaction mechanisms, a direct reaction mechanism in the abstract channel and long lifetime indirect mechanism in the exchange channel, respectively. During the reaction, the collision energy could be efficiently transferred to vibration of the D2 product in the abstract reaction channel and rotation of the DAu product in the exchange channel.

Quantum Wave Packet Study of the H + Br2 → HBr + Br Reaction on a New Ab Initio Potential Energy Surface.

An accurate global potential energy surface (PES) for the HBr2 system has been constructed using the fundamental invariant neural network fitting method based upon 11 698 ab initio energies at the UCCSD(T)/CBS level of theory, with the spin-orbit coupling of the 2P3/2 orbit of the Br atom properly included. The time-dependent wave packet calculations have been performed to study the H + Br2 → HBr + Br reaction on the new PES. The total reaction probabilities for total angular momentum J = 0 for the ground initial state show no threshold due to the submerged barrier height (-0.351 kcal/mol) of the PES. The total integral cross sections (ICS) for reactant Br2 in ro-vibrational states (v0 = 0, j0 = 0, 10, 20, 30; v0 = 1-5, j0 = 0) were calculated for collision energy of up to 0.5 eV. It is found that the initial rotational excitation has a negligible effect on the ICS, and the initial vibrational excitation depresses the reactivity to some extent. The thermal rate constants for the title reaction in the temperature range of 100-1000 K were calculated from the Boltzmann averaging of the v0 = 0-5 rate constants, which overestimated the experimental results to some extent.

State-to-state dynamics of reactions H + DH’(ν = 0,j = 0) → HH’(ν’,j’) + D/HD(ν’,j’) + H’ with time-dependent quantum wave packet method* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11504206 and 12004216), the Ph. D. Research Start-up Fund of Shandong Jiaotong University (Grant No. BS2020025), and the Shandong Natural Science Foundation, China (Grant Nos.

State-to-state time-dependent quantum dynamics calculations have been carried out to study H + DH’ → HH’ + D/HD + H’ reactions on BKMP2 surface. The total integral cross sections of both reactions are in good agreement with earlier theoretical and experimental results, moreover the rotational state-resolved reaction cross sections of H + DH’ → HH’ + D at collision energy E C = 0.5 eV are closer to the experimental values than the ones calculated by Chao et al. [J. Chem. Phys. 117 8341 (2002)], which proves the higher precision of the quantum calculation in this work. In addition, the state-to-state dynamics of H + DH’ → HD’ + H reaction channel have been discussed in detail, and the differences of the micro-mechanism of the two reaction channels have been revealed and analyzed clearly.

Charge Transfer Processes for H + H2+ Reaction Employing Coupled 3D Wavepacket Approach on Beyond Born-Oppenheimer Based Ab Initio Constructed Diabatic Potential Energy Surfaces.

The dynamics of the H + H2+ reaction has been analyzed from the electronically first excited state of diabatic potential energy surfaces constructed by employing the Beyond Born-Oppenheimer theory [J. Chem. Phys. 2014, 141, 204306]. We have employed the coupled 3D time-dependent wavepacket formalism in hyperspherical coordinates for multisurface reactive scattering problems. To be specific, the charge transfer processes have been investigated extensively by calculating state-to-state as well as total reaction probabilities and integral cross sections, when the reaction process is initiated from the first excited electronic state (21A'). We have depicted the convergence profiles of reaction probabilities for the competing charge transfer processes, namely, reactive charge transfer (RCT) and nonreactive charge transfer (NRCT) processes for different total energies with respect to total angular momentum, J. Total and state-to-state integral cross sections are calculated as a function of total energy for the initial rovibrational state, namely, v = 0, j = 0 level of H2+ (2Σg+) molecule and are compared with previous theoretical calculations. Finally, we have calculated temperature-dependent rate constants using our presently evaluated cross sections and compared their average with the experimentally measured one.

Production of transuranium isotopes in Ne20 -induced incomplete fusion reactions

Using a semiclassical dynamical model that combines a classical trajectory model with stochastic breakup with a dynamical fragmentation theory treatment of two-body clusterization and decay of a projectile, results are presented for $^{20}\mathrm{Ne}$-induced incomplete fusion reactions for the production of superheavy elements. Targets include $^{247,248,250}\mathrm{Cm}$ and $^{251,252,254}\mathrm{Cf}$, and results include angular, excitation energy, and angular momentum distributions in addition to total integrated cross sections for heavy incomplete fusion products. The results show that at Coulomb energies, the studied Cf isotopes are generally the more favorable choice of target over the studied Cm isotopes for the production of `colder' and more stable $^{263}\mathrm{Lr}$, $^{263,264,266}\mathrm{Rf}$, and $^{265}\mathrm{Db}$ isotopes through the incomplete fusion mechanism. Also presented are evaporation residue cross sections for the dominant primary incomplete fusion products of each of the six reactions: $^{263,264,266}\mathrm{Rf}$ and $^{267,268,270}\mathrm{Sg}$, as well as for the primary incomplete fusion products $^{269,270,272}\mathrm{Bh}$.

Electron impact ionization cross sections of C2H4 molecule

In this paper, we have investigated partial and total integral ionization cross sections of C2H4 molecule by Jain-Khare semiempirical approach during the electron impact. They show good agreement with available data. Besides integral ionization cross sections, the first time we have evaluated its partial and total single and double differential cross sections. No other results are available for single differential cross sections and double differential cross sections to compare the present results calculated.

State-to-state dynamics of S+(2D) + H2(X1Σg+)(v, j) collision reaction based on the H2S+ (X2A′′)potential energy surface

The state-to-state dynamics of the S+(2D) + H2(X1Σg+)(v, j) collision reaction is investigated on the H2S+(X2A″) potential energy surface by using the quasi-classical trajectory (QCT) method. The obtained total integral cross section (ICS) and rate constant of the reaction display obvious vibrational excitation effect. The differential cross sections show the effect of vibrational excitation, collision energy and deep well of potential energy surface. A comparison of the state-to-state ICSs from QCT method with the ones from quantum mechanical method proves the validity of QCT calculations. The further exploration of state-resolved ICSs and rate constants for different vibrational quantum numbers of reactant indicates that (i) the higher rotational state of product is much easier to form; (ii) the width of product molecule excited state distribution is obviously enlarged by the vibrational excitation of reactant.

Mechanism analysis of reaction based on the quantum state-to-state dynamics**Project supported by the National Natural Science Foundation of China (Grant No. 11674198), the Taishan Scholar Project of Shandong Province, China (Grant No. ts201511025), and the Science Fund from the Shandong Provincial Laboratory of Biophysics.

We present a state-to-state dynamical calculation on the reaction S++H2→ SH+ + H based on an accurate X2A″ potential surface. Some reaction properties, such as reaction probability, integral cross sections, product distribution, etc., are found to be those with characteristics of an indirect reaction. The oscillating structures appearing in reaction probability versus collision energy are considered to be the consequence of the deep potential well in the reaction. The comparison of the present total integral cross sections with the previous quasi-classical trajectory results shows that the quantum effect is more important at low collision energies. In addition, the quantum number inversion in the rotational distribution of the product is regarded as the result of the heavy–light–light mass combination, which is not effective for the vibrational excitation. For the collision energies considered, the product differential cross sections of the title reaction are mainly concentrated in the forward and backward regions, which suggests that there is a long-life intermediate complex in the reaction process.

Exploring reaction mechanism and vibrational excitation effect in H + CH([formula omitted] = 0) reaction

The reaction mechanism and vibrational excitation effect in H + CH → C + H2 reaction is analyzed in detail by utilizing quasi-classical trajectory method. The capture time, vibrational excitation effect for the total integral cross sections (ICSs), rate constants, and rovibrational state resolved ICSs are studied. Results show that with the collision energy increasing, the direct mechanism is becoming increasingly important, but, the indirect mechanism is still important and even dominant. The analysis of the ICSs according to the maximum impact parameter and probability lets us to get a deep insight into the effect of vibration excitation on reaction.