Statistical adiabatic channel model for termolecular reactions.

In this work, we present a statistical adiabatic channel model for termolecular reactions, A + B + C → Products. Our approach relies on hyperspherical coordinates, where the adiabatic channels are readily defined in the hyper-radius after averaging the hyperangular degrees of freedom. In this way, we find a general expression for termolecular rate constants.

Sulfur recombination: A direct approach.

This work presents a direct three-body recombination approach of the sulfur recombination reaction, S + S + M → S2 + M, at temperatures between 100 and 500 K. Our calculations for M = Ar, based on a classical trajectory approach in hyperspherical coordinates, show excellent agreement with the experimental measurement at T = 298 K of Fair and Thrush [Trans. Faraday Soc.

Alignment transport between ultracold polar molecules.

We propose an array of ultracold polar molecules as a platform to study alignment transport between molecules. We envision a polar molecule being aligned with an intense off-resonant laser field whose alignment migrates to a nearby molecule due to dipole-dipole interactions. Our results show that the transport of the alignment is due to a complex interplay between electric field-driven excitations and dipole-dipole interactions.

Collisional alignment and molecular rotation control the chemi-ionization of individual conformers of hydroquinone with metastable neon.

The relationship between the shape of a molecule and its chemical reactivity is a central tenet in chemistry. However, the influence of the molecular geometry on reactivity can be subtle and result from several opposing effects. Here, using a crossed-molecular-beam experiment in which individual rotational quantum states of specific conformers of a molecule are separated, we study the chemi-ionization reaction of hydroquinone with metastable neon atoms.

Predicting early complications in patients with spinal gunshot wounds: A multicenter study.

Introduction: There is a wide variation in the clinical presentation of spinal gunshot wounds ranging from isolated minor stable fractures to extremely severe injuries with catastrophic neurological damage.

Research Question: we aim to analyze the risk factors for early complications and impact of surgical treatment in patients with spinal gunshot wounds.

Material And Methods: This is a multicentre retrospective case-control study to compare patients with spinal gunshot wounds who had early complications with those who did not.

Py3BR: A software for computing atomic three-body recombination rates.

The three-body recombination reaction, or ternary association, is a termolecular reaction leading to a molecule after a three-body encounter that plays a vital role in many relevant scenarios in chemical physics. Here, we introduce the Python 3-Body Recombination program, which is dedicated to the computation of atomic three-body recombination rate coefficients. The software is based on a classical trajectory approach in hyperspherical coordinates after mapping the three-body problem as a single particle in a higher-dimensional space.

On the role of non-additive interactions in three-body recombination.

Non-additive forces are a cornerstone of molecular spectroscopy and reaction dynamics. However, the relevance of non-additive forces in three-body recombination remains largely unexplored. In this work, we present a global study on the impact of non-additive interactions in three-body recombination: atom-atom-atom and ion-atom-atom.

AlF-AlF Reaction Dynamics between 200 K and 1000 K: Reaction Mechanisms and Intermediate Complex Characterization.

AlF is a relevant molecule in astrochemistry as a tracer of F-bearing molecules. Additionally, AlF presents diagonal Franck-Condon factors and can be created very efficiently in the lab, which makes it a prototypical molecular for laser cooling. However, very little is known about the reaction dynamics of AlF.

Molecular dynamics-driven global potential energy surfaces: Application to the AlF dimer.

In this work, we present a full-dimensional potential energy surface for AlF-AlF. We apply a general machine learning approach for full-dimensional potential energy surfaces, employing an active learning scheme trained on ab initio points, whose size grows based on the accuracy required. The training points are selected based on molecular dynamics simulations, choosing the most suitable configurations for different collision energy and mapping the most relevant part of the potential energy landscape of the system.

Trap-Assisted Complexes in Cold Atom-Ion Collisions.

We theoretically investigate the trap-assisted formation of complexes in atom-ion collisions and their impact on the stability of the trapped ion. The time-dependent potential of the Paul trap facilitates the formation of temporary complexes by reducing the energy of the atom, which gets temporarily stuck in the atom-ion potential. As a result, those complexes significantly impact termolecular reactions leading to molecular ion formation via three-body recombination.

Barrier Height Prediction by Machine Learning Correction of Semiempirical Calculations.

Different machine learning (ML) models are proposed in the present work to predict density functional theory-quality barrier heights (BHs) from semiempirical quantum mechanical (SQM) calculations. The ML models include a multitask deep neural network, gradient-boosted trees by means of the XGBoost interface, and Gaussian process regression. The obtained mean absolute errors are similar to those of previous models considering the same number of data points.

The performance of CCSD(T) for the calculation of dipole moments in diatomics.

This work analyzes the accuracy of the coupled cluster with single, double, and perturbative triple excitation [CCSD(T)] method for predicting dipole moments. In particular, we benchmark CCSD(T) predictions for the equilibrium bond length, vibrational frequency, and dipole moment accurate experimental data. As a result, we find that CCSD(T) leads to accurate dipole moments.

Ion-atom-atom three-body recombination: From the cold to the thermal regime.

We present a study on ion-atom-atom reaction A + A + B in a wide range of systems and collision energies ranging from 100 μK to 10 K, analyzing two possible products: molecules and molecular ions. The dynamics is performed via a direct three-body formalism based on a classical trajectory method in hyperspherical coordinates developed in Pérez-Ríos et al. [J.

Spinal canal invasion as a predictor of neurological deficit in traumatic vertebral burst fractures.

Background: This study correlated the extent of spinal canal compression from retropulsed traumatic burst cervical, thoracic, and lumbar spine fractures with the severity of neurological dysfunction.

Methods: One hundred and sixty-nine patients with cervical, thoracic, or lumbar sub-axial traumatic burst fractures were seen in an emergency department from 2019 to 2021; 79.3% were men, averaging 37 years of age.

The chemistry of AlF and CaF production in buffer gas sources.

In this work, we explore the role of chemical reactions on the properties of buffer gas cooled molecular beams. In particular, we focus on scenarios relevant to the formation of AlF and CaF via chemical reactions between the Ca and Al atoms ablated from a solid target in an atmosphere of a fluorine-containing gas, in this case, SF and NF. Reactions are studied following an ab initio molecular dynamics approach, and the results are rationalized following a tree-shaped reaction model based on Bayesian inference.

On the relationship between spectroscopic constants of diatomic molecules: a machine learning approach.

Through a machine learning approach, we show that the equilibrium distance, harmonic vibrational frequency and binding energy of diatomic molecules are related, independently of the nature of the bond of a molecule; they depend solely on the group and period of the constituent atoms. As a result, we show that by employing the group and period of the atoms that form a molecule, the spectroscopic constants are predicted with an accuracy of <5%, whereas for the A-excited electronic state it is needed to include other atomic properties leading to an accuracy of <11%.

Spectroscopic characterization of the aΠ state of aluminum monofluoride.

Spectroscopic studies of aluminum monofluoride (AlF) have revealed its highly favorable properties for direct laser cooling. All Q lines of the strong AΠ ← XΣ transition around 227 nm are rotationally closed and thereby suitable for the main cooling cycle. The same holds for the narrow, spin-forbidden aΠ ← XΣ transition around 367 nm, which has a recoil limit in the µK range.

Ozone Formation in Ternary Collisions: Theory and Experiment Reconciled.

The present Letter shows that the formation of ozone in ternary collisions O+O_{2}+M-the primary mechanism of ozone formation in the stratosphere-at temperatures below 200 K (for M=Ar) proceeds through a formation of a temporary complex MO_{2}, while at temperatures above ∼700  K, the reaction proceeds mainly through a formation of long-lived vibrational resonances of O_{3}^{*}. At intermediate temperatures 200-700 K, the process cannot be viewed as a two-step mechanism, often used to simplify and approximate collisions of three atoms or molecules. The developed theoretical approach is applied to the reaction O+O_{2}+Ar because of extensive experimental data available.

Observation of Chemical Reactions between a Trapped Ion and Ultracold Feshbach Dimers.

We measure chemical reactions between a single trapped ^{174}Yb^{+} ion and ultracold Li_{2} dimers. This produces LiYb^{+} molecular ions that we detect via mass spectrometry. We explain the reaction rates by modeling the dimer density as a function of the magnetic field and obtain excellent agreement when we assume the reaction to follow the Langevin rate.

Classical threshold law for the formation of van der Waals molecules.

We study the role of pairwise long-range interactions in the formation of van der Waals molecules through direct three-body recombination processes A + B + B → AB + B, based on a classical trajectory method in hyperspherical coordinates developed in our earlier works [J. Pérez-Ríos et al., J.

Complex Reaction Network Thermodynamic and Kinetic Autoconstruction Based on Statistical Mechanics: A Case Study of O Activation on Ag Clusters.

An approach based on statistical mechanics is demonstrated for autoconstructing complex reaction networks. molecular dynamics combined with Markov state models are employed to study relevant transitions and corresponding thermodynamic and kinetic properties of a reaction. To explore the capability and flexibility of this approach, we present a study of oxygen activation on Ag as a model reaction.

On the formation of van der Waals complexes through three-body recombination.

In this work, we show that van der Waals molecules X-RG (where RG is the rare gas atom) may be created through direct three-body recombination collisions, i.e., X + RG + RG → X-RG + RG.

Predicting second virial coefficients of organic and inorganic compounds using Gaussian process regression.

We show that by using intuitive and accessible molecular features it is possible to predict the temperature-dependent second virial coefficient of organic and inorganic compounds with Gaussian process regression. In particular, we built a low dimensional representation of features based on intrinsic molecular properties, topology and physical properties relevant for the characterization of molecule-molecule interactions. The featurization was used to predict second virial coefficients in the interpolative regime with a relative error ⪅1% and to extrapolate the prediction to temperatures outside of the training range for each compound in the dataset with a relative error of 2.

The diatomic molecular spectroscopy database.

Motivation: The spectroscopy of diatomic molecules is an important research area in chemical physics due to its relevance in astrochemistry, combustion chemistry, and ultracold physics. However, there is currently no database where the user can easily retrieve, in a useful format, the spectroscopic constants of a given molecule. A similar situation appears concerning the vibrational Franck-Condon factors for diatomic molecules, a crucial parameter to infer laser cooling prospects for molecules.