The calculation of the anharmonic modes small- to medium-sized molecules for assigning experimentally measured frequencies corresponding type molecular motions is computationally challenging at sufficiently high levels quantum chemical theory. Here, a practical and affordable way calculate coupled-cluster quality using second-order vibrational perturbation theory (VPT2) from machine-learned models presented. approach, referenced as "NN + VPT2", uses high-dimensional neural network (PhysNet)...

Feshbach resonances are fundamental to interparticle interactions and become particularly important in cold collisions with atoms, ions, molecules. Here we present the detection of a benchmark system for strongly interacting highly anisotropic -- molecular hydrogen ions colliding noble gas atoms. The launched by Penning ionization exclusively populating that span both short- long-range parts interaction potential. We resolved all final channels tomographic manner using ion-electron...

The decomposition dynamics of vibrationally excited syn-CH3CHOO to form vinoxy + hydroxyl (CH2CHO OH) radicals or recombine glycolaldehyde (CH2OHCHO) are characterized using statistically significant numbers molecular simulations a full-dimensional neural-network-based potential energy surface at the CASPT2 level theory. computed final OH-translational and rotational state distributions agree well with experiments probe still unknown O-O bond strength DeOO for which best values from 22 25...

The full reaction pathway between the syn-CH3CHOO Criegee Intermediate via vinyl hydroxyperoxide (VHP) to CH2COH+OH is followed for vibrationally excited and thermally prepared reactants. Reactivity along entire was characterized from an aggregate of more than 10 μs reactive MD simulations using energy functions with accuracies at Møller–Plesset second order level theory. Reaction times OH elimination are on nanosecond time scale, dependence rates consistent experiments in jet. actual depend...

The kinetics of MgO+ + CH4 was studied experimentally using the variable ion source, temperature adjustable selected flow tube (VISTA-SIFT) apparatus from 300-600 K and computationally by running analyzing reactive atomistic simulations. Rate coefficients product branching fractions were determined as a function temperature. reaction proceeded with rate k = 5.9 ± 1.5 × 10-10(T/300 K)-0.5±0.2 cm3 s-1. MgOH+ dominant at all temperatures, but Mg+, co-product oxygen-atom transfer to form...

The reaction dynamics of H 2 COO to form HCOOH and dioxirane as first steps for OH-elimination are quantitatively investigated.

Context. The dynamics of molecule formation, relaxation, diffusion, and desorption on amorphous solid water (ASW) is studied in a quantitative fashion. Aims. formation probability, stabilization, energy diffusion CO 2 NO cold ASW following atom+diatom recombination reactions are characterized quantitatively. Methods. Accurate machine-learned functions combined with fluctuating charge models were used to investigate the interactions, atomic oxygen ASW. Energy relaxation into internal degrees...

The formation of molecules in and on amorphous solid water (ASW) as it occurs interstellar space releases appreciable amounts energy that need to be dissipated the environment. Here, transfer between CO2 formed within surface surrounding is studied. Following CO(1Σ+) + O(1D) recombination average translational internal increases ∼10 ps time scale by 15-25% depending whether reaction takes place or an cavity ASW. Due tight coupling exhibits a peak at early times which present for but absent...

Understanding the formation of molecules under conditions relevant to interstellar chemistry is fundamental characterize chemical evolution universe. Using reactive molecular dynamics simulations with model-based or high-quality potential energy surfaces provides a means specifically and quantitatively probe individual reaction channels at level. The CO2 from collision CO(1Σ) O(1D) characterized on amorphous solid water (ASW) typical in cold clouds. Recombination takes place subnanosecond...

The dynamics of the C( 3 P) + O 2 ( Σ−g) → CO( 1 Σ ) O( D) reaction on its electronic ground state is investigated by using time-dependent wave packet propagation (TDWP) and quasi-classical trajectory (QCT) simulations.

The reaction dynamics of H$_2$COO to form linear HCOOH and dioxirane as first steps for OH-elimination is quantitatively investigated. Using a machine learned potential energy surface at the CASPT2/aug-cc-pVTZ level theory vibrational excitation along CH-normal mode $\nu_{\rm CH}$ with energies up 40.0 kcal/mol ($\sim 5 \nu_{\rm CH}$) leads almost exclusively which further decomposes into OH+HCO. Although barrier only 21.4 probability two orders magnitude lower if CH-stretch excited....

\noindent \textit{Context. }The dynamics for molecule formation, relaxation, diffusion, and desorption on amorphous solid water is studied in a quantitative fashion. \textit{Aims. }We aim at characterizing, level, the formation probability, stabilization, energy relaxation diffusion of CO$_2$ NO$_2$ cold following atom+diatom recombination reactions. \textit{Methods. }Accurate machine-learned functions combined with fluctuating charge models were used to investigate interactions, atomic...

Quantum resonances in collisions and reactions are a sensitive probe of the intermolecular forces. They may dominate final quantum state distribution, as recently observed for Feshbach cold collision experiment (Science 380, 77 (2023)). This raises question whether sensitivity such measurements is sufficient to assess quality theoretical models interaction. We here compare measured cross sections those obtained with exact coupled-channels scattering calculations three different ab initio...

Understanding the formation of molecules under conditions relevant to interstellar chemistry is fundamental characterize chemical evolution universe. Using reactive molecular dynamics simulations with model-based or high-quality potential energy surfaces provides a means specifically and quantitatively probe individual reaction channels at level. The CO$_2$ from collision CO($^1 \Sigma$) O($^1$D) characterized on amorphous solid water (ASW) typical in cold clouds. Recombination takes place...

The calculation of the anharmonic modes small to medium sized molecules for assigning experimentally measured frequencies corresponding type molecular motions is computationally challenging at sufficiently high levels quantum chemical theory. Here, a practical and affordable way calculate coupled-cluster quality using second order vibrational perturbation theory (VPT2) from machine-learned models presented. approach, referred as "NN + VPT2", uses high-dimensional neural network (PhysNet)...

The decomposition and chemical dynamics for vibrationally excited syn-CH$_3$CHOO is followed based on statistically significant numbers of molecular simulations. Using a neural network-based reactive potential energy surface, transfer learned to the CASPT2 level theory, final total kinetic release rotational state distributions OH fragment are in quantitative agreement with experiment. In particular widths these sensitive experimentally unknown strength O--O bond strength, which values $D_e...

Feshbach resonances are fundamental to interparticle interactions and become particularly important in cold collisions with atoms, ions, molecules. Here we present the detection of a benchmark system for strongly interacting highly anisotropic -- molecular hydrogen ions colliding noble gas atoms. The launched by Penning ionization exclusively populating that span both short- long-range parts interaction potential. We resolved all final channels tomographic manner using ion-electron...