Jesús Pérez-Ríos

The birth of a new phase is usually described thermodynamically, but in the gas phase it begins as chemistry.

We investigate the microsolvation of primary alkylamines using electronic-structure calculations. For monohydrated complexes, the amino group acts as the dominant hydrogen-bond acceptor, yielding an intermediate-to-moderate hydrogen bond that saturates beyond hexylamine. Stepwise hydration indicates marked stabilization upon incorporation of the third water molecule, concomitant with shortening of the hydrogen-bond distances, consistent with hydrogen-bond cooperativity. Additional water molecules lead to progressively more intricate hydrogen-bonded networks and a pronounced dependence on alkyl-chain length for hexylamine and higher homologs. Collectively, these results indicate that alkylamine hydration behavior emerges from the interplay between water–water hydrogen bonding and alkylamine–water interactions.

Phys. Rev. A 114, 029901 (2026)

Spanning energy regimes from ultracold atoms to plasma chemistry, this concise volume presents a unified treatment of termolecular reaction dynamics, integrating statistical models, direct three-body recombination, and classical mechanisms such as Lindemann–Hinshelwood. With applications ranging from atmospheric ozone formation to hydrogen combustion and ion solvation, the book bridges theory and experiment across chemical physics, physical chemistry, and molecular dynamics. Each chapter critically evaluates theoretical frameworks against experimental data, highlighting open questions and future directions. Designed for postgraduate students and researchers, this accessible yet rigorous text consolidates decades of scattered literature into a single, authoritative resource. Written by Jesús Pérez-Ríos, a leading figure in molecular reaction theory, this volume is essential reading for anyone seeking to understand or model complex reaction pathways in gas-phase chemistry.

Minimal atomic dark matter with its distinctive cooling mechanisms offers an instructive framework for understanding the potential impact of dark matter on small-scale structure formation and early cosmology. The model consists of two fermions with opposite charges under a hidden Abelian gauge symmetry U (1) _D and masses m p _D and m e _D , respectively. Analogous to hydrogen in the Standard Model, these fermions interact via their own electromagnetic-like force, with a dark fine structure constant denoted by α _D , and can bind into neutral atomic (and molecular) dark states. Previous work has largely focused on the benchmark scenario where the dark sector mirrors ordinary matter, with m e _D near the electron mass, m p _D near the proton mass, and α _D ∼ 1/137. We extend this analysis by investigating dark recombination and cooling physics across the full parameter space of masses and couplings. Combining Cosmic Microwave Background (CMB) measurements from Planck and ACT with BAO and Pantheon+ data, we place new constraints on the atomic dark matter parameter space, identifying regions where acoustic damping and recombination dynamics leave observable imprints on the CMB.

For over a century, termolecular (third-order) chemical reactions have been explained by the Lindemann–Hinshelwood mechanism, assuming sequential stabilization via bimolecular encounters. Here, we demonstrate that barrierless termolecular reactions are fundamentally governed by direct three-body dynamics. Using classical trajectory calculations in hyperspherical coordinates, we quantitatively reproduce ion-atom recombination kinetics across a wide temperature range without invoking intermediate complexes or steady-state assumptions. Our results not only resolve longstanding discrepancies between theory and experiment, but also establish a general mechanistic framework for barrierless termolecular reactions, with implications spanning atmospheric chemistry, plasma physics, and ultracold chemistry.

We present a machine learning model to predict the electric dipole moment of diatomic molecules using only the atomic properties of the constituent atoms. The model can screen the entire periodic table to identify the molecules with the largest dipole moments for applications in cold molecular sciences or to find the molecule with the largest dipole moment that contains a given atom. Similarly, our model identifies useful trends that explain molecular dipole moments, improving our intuition in chemical physics beyond the paradigm of electronegativity differences. Finally, we condense our model into an analytical expression to predict the dipole moment in terms of atomic properties.