ABC: a quantum reactive scattering program

This review discusses recent quantum scattering calculations on bimolecular chemical reactions in the gas phase. This theory provides detailed and accurate predictions on the dynamics and kinetics of reactions containing three atoms. In addition, the method can now be applied to reactions involving polyatomic molecules. Results obtained with both time-independent and time-dependent quantum dynamical methods are described. The review emphasises the recent development in time-dependent wave packet theories and the applications of reduced dimensionality approaches for treating polyatomic reactions. Calculations on over 40 different reactions are described.

Quantum scattering calculations on chemical reactions.

A three-dimensional (3D) ion velocity imaging method was developed to measure the product velocity distributions in crossed molecular beam experiments. While maintaining conventional two-dimension velocity mapping, the third velocity component was mapped linearly to the ion time of flight. A weak extraction field was used to spread the ion turnaround time to several hundred nanoseconds, which permits good resolution for selection of the longitudinal velocity. A fast gated (⩾5 ns) intensified charge coupled device camera was used to record time-sliced ion images. Calibration of the apparatus was done by measuring O+ images from the multiphoton dissociation/ionization of O2. The resolution in velocity achieved was about 1% (Δv/v) in slicing through the center of a Newton sphere. The overall performance was examined by observing product ion images from the F+CD4→DF+CD3 reaction. To detect CD3+ with kinetic energy release of about 1 eV, 50 ns time slicing provides sufficient velocity resolution, such that res...

Application of time-sliced ion velocity imaging to crossed molecular beam experiments

The recent development of a range of new methods for producing samples of gas-phase molecules that are translationally cold ( K) or ultracold ( mK) is driving efforts to study reactive and inelastic collisional processes in these temperature regimes. In this review article the new methods for cold/ultracold molecule production are reviewed in the context of their potential or current use in collisional studies and progress in the application of these methods is highlighted. In these sub-Kelvin temperature ranges, where the de Broglie wavelength is long compared with molecular dimensions, quantum effects may play a crucial role in the collision dynamics. Reactions with no potential energy barrier are of greatest importance, and this review article summarizes some of the principal theoretical approaches to understanding quantum effects in these barrierless processes.

/pdf/ultracold-molecules-and-ultracold-chemistry-4mknd6ljfd.pdf

Ultracold molecules and ultracold chemistry

Reaction resonances, or transiently stabilized transition-state structures, have proven highly challenging to capture experimentally. Here, we used the highly sensitive H atom Rydberg tagging time-of-flight method to conduct a crossed molecular beam scattering study of the F + H2 --> HF + H reaction with full quantum-state resolution. Pronounced forward-scattered HF products in the v' = 2 vibrational state were clearly observed at a collision energy of 0.52 kcal/mol; this was attributed to both the ground and the first excited Feshbach resonances trapped in the peculiar HF(v' = 3)-H' vibrationally adiabatic potential, with substantial enhancement by constructive interference between the two resonances.

https://science.sciencemag.org/content/sci/311/5766/1440.full.pdf

Observation of Feshbach Resonances in the F+ H2 → HF +H Reaction

Conclusive evidence is presented for the existence of a reactive resonance in the $\mathrm{F}+\mathrm{HD}$ reaction. In a molecular beam experiment, the resonance appears in the integral cross section as a distinct steplike feature, while in the differential cross section it is manifested as sharply varying forward-backward peaks in the product distribution. A detailed analysis of the quantum dynamics establishes that a reactive resonance localized in the transition-state region is responsible for these remarkable observations. At collision energies below $1\mathrm{kcal}/\mathrm{mol}$, the reaction proceeds almost exclusively through resonant tunneling with very little contribution from the more conventional direct mechanism.

Resonance-mediated chemical reaction: F+HD-->HF+D

We have studied the reaction F+HD at low collision energies using a combination of experimental and theoretical methods. Clear evidence for a reactive resonance is found in the integral cross section for the reactive channel F+HD→HF+D. Using a crossed molecular beam apparatus, the total reactive cross sections for the HF+D and DF+H channels were obtained in the collision energy range of 0.2–5 kcal/mol. In addition, Doppler profiles were obtained over this range of energies, which provide information about the angularly resolved distribution of final vibrational states. The cross section shows a distinctive steplike feature near 0.5 kcal/mol. Furthermore, the Doppler profiles reveal a dramatic change in the angular distribution of products over a narrow energy range centered at 0.5 kcal/mol. This feature is shown to arise from a reactive resonance localized near the transition state. Theoretical scattering calculations have been carried out using the Stark–Werner potential energy surface, which accurately ...

Observation of a transition state resonance in the integral cross section of the F+HD reaction

Complementary to our recent report on the F+HD reaction, the reactive excitation functions for the other isotopomers are presented. Through analysis of the differential cross section data, the collisional energy dependencies of product vibrational branchings for F+HD are also reported here. Several important conclusions can be drawn from this work. First, the transition-state properties, in particular the barrier height, of this reaction are well-characterized by the SW PES, despite its neglect of spin–orbit couplings. Second, contrary to the theoretical conclusion in recent literatures, an experimental observation is presented which seems to suggest that a resonance may indeed exist for the F+H2 reaction in support of the original interpretation proposed by Lee and co-workers. Third, the vibrational branching for the F+HD→HF+D reaction elucidates another facet of resonance effects in the integral cross sections. Finally, the nonadiabatic reactivity of the spin–orbit excited F*(2P1/2) atom is found to be small, which is in line with the conclusion inferred from a most recent, full quantum mechanical multisurface calculation.

Reactive excitation functions for F+p-H2/n-H2/D2 and the vibrational branching for F+HD

By exploiting two different Cl-beam sources and concurrently monitoring the concentrations of the two reagents [Cl(2P3/2) and Cl*(2P1/2)] and the H- or D-atom product, the spin-orbit specific excitation functions of the title reactions were determined. The exceptionally large nonadiabatic reactivity for Cl*(2P1/2)+n-H2, inferred in our previous differential cross section investigation, is now confirmed and quantified. The isotope effects for both the spin-orbit ground and excited reagents are also elucidated.

Direct determination of the spin-orbit reactivity in Cl(2P3/2,2P1/2)+H2/D2/HD reactions

The complete state-resolved differential cross section σ(v′,j′,θ;Ec), investigated in a crossed-beam scattering study, is presented for the title reaction at six initial collision energies (Ec) which are below or near the barrier energy. At low energies, all reactive flux is gated through a trapped resonance state via a tunneling process. Hence, it serves as a benchmark system for better understanding the reactive resonance phenomenon. In addition to highlighting various resonance fingerprints of experimental observable, the concept of resonant tunneling reaction mechanism is elucidated. Particular emphasis is placed on its distinction from the more conventional transition-state reaction mechanism.

Reaction dynamics of F+HD→HF+D at low energies: Resonant tunneling mechanism

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Feng Dong

Author Tools

Chat about Author