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Roaming reactions involving a neutral fragment of a molecule that transiently wanders around another fragment before forming a new bond are intriguing and peculiar pathways for molecular rearrangement. Such reactions can occur for example…

We provide a dynamical interpretation of the recently identified `roaming' mechanism for molecular dissociation reactions in terms of geometrical structures in phase space. These are NHIMs (Normally Hyperbolic Invariant Manifolds) and their…

Recent studies have found an unusual way of dissociation in formaldehyde. It can be characterized by a hydrogen atom that separates from the molecule, but instead of dissociating immediately it roams around the molecule for a considerable…

Dynamical Systems · Mathematics 2019-11-18 Vladimir Krajnak , Holger Waalkens

A reduced two dimensional model is used to study Ketene isomerization reaction. In light of recent results by Ulusoy \textit{et al.} [J.\ Phys.\ Chem.\ A {\bf 117}, 7553 (2013)], the present work focuses on the generalization of the roaming…

A model Hamiltonian for the reaction CH$_4^+ \rightarrow$ CH$_3^+$ + H, parametrized to exhibit either early or late inner transition states, is employed to investigate the dynamical characteristics of the roaming mechanism. Tight/loose…

Chemical Physics · Physics 2015-06-18 F. A. L. Mauguière , P. Collins , G. S. Ezra , S. C. Farantos , S. Wiggins

We consider the roaming mechanism for chemical reactions under the nonholonomic constraint of constant kinetic energy. Our study is carried out in the context of the Hamiltonian isokinetic thermostat applied to Chesnavich's model for an…

Chaotic Dynamics · Physics 2019-12-11 Vladimír Krajňák , Gregory S. Ezra , Stephen Wiggins

Although the amino acid tyrosine is among the main building blocks of life, its photochemistry is not fully understood. Traditional theoretical simulations are neither accurate enough, nor computationally efficient to provide the missing…

Water mediates a broad range of chemical reactions, including proton transfer, bond rearrangement, and conventional radical processes, defining a continuously expanding repertoire of intrinsic reactivity. However, roaming, a fundamental…

Chemical Physics · Physics 2026-03-16 Rui Liu , Baiqiang Liu , Zhen Gong , Zhaohua Cui , Yue Feng , Zhigang Wang

We report a femtosecond time-resolved strong-field study of ammonia borane (AB, BH3NH3) following both single and double ionization, revealing ultrafast fragmentation dynamics and hydrogen release. Mass spectrometry, combined with fragment…

Chemical Physics · Physics 2026-01-07 Sung Kwon , Naga Krishnakanth Katturi , Bruno I. Moreno , Carlos Cárdenas , Marcos Dantus

Fragments from organic molecule dissociation (such as reactive ions and radicals) can form interstellar complex molecules like amino acids. The goal of this work is to experimentally study photoionization and photodissociation processes of…

Astrophysics · Physics 2007-05-23 S. Pilling , A. C. F. Santos , H. M. Boechat-Roberty

We report a combined experimental and theoretical study on the formation of O2+ by electronimpact double ionization and fragmentation of carbon dioxide (CO2) molecule. Through fragment ions and electron coincidence momentum imaging, we…

Atomic and Molecular Clusters · Physics 2025-09-09 Qibo Ma , Xintai Hao , Jiaqi Zhou , Xiaorui Xue , Qingrui Zeng , Peng Li , Lei Wang , Xueguang Ren

We demonstrate the breakdown of molecular-frame dynamics induced by the uncoupling of molecular rotation from electronic motion in molecular Rydberg states. We observe this non-Born-Oppenheimer regime in the time domain through…

Atomic and Molecular Clusters · Physics 2017-07-05 Lucas J. Zipp , Adi Natan , Philip H. Bucksbaum

We present experimental results for dissociative electron attachment to acetylene near the 3 eV $^2\Pi_g$ resonance. In particular, we use an ion-momentum imaging technique to investigate the dissociation channel leading to C$_2$H$^-$…

Chemical Physics · Physics 2014-10-29 M. Fogle , D. J. Haxton , A. L. Landers , A. E. Orel , T. N. Rescigno

Chesnavich's model Hamiltonian for the reaction CH$_4^+ \rightarrow$ CH$_3^+$ is known to exhibit a range of interesting dynamical phenomena including roaming. The model system consists of two parts: a rigid, symmetric top representing the…

Dynamical Systems · Mathematics 2019-11-18 Vladimir Krajnak , Stephen Wiggins

We investigate how vibration affects molecular photoemission dynamics, through simulations on two-dimension asymmetric model molecules including the electronic and nuclear motions in a fully correlated way. We show that a slight anisotropy…

Chemical Physics · Physics 2024-02-14 Antoine Desrier , Morgan Berkane , Camille Lévêque , Richard Taïeb , Jérémie Caillat

Fragmentation of highly charged molecular ions or clusters consisting of more than two atoms can proceed in an onestep synchronous manner where all bonds break simultaneously or sequentially by emitting one ion after the other. We separated…

We consider a basic model of the lossless interaction between a moving two-level atom and a standing-wave single-mode laser field. Classical treatment of the translational atomic motion provides the semiclassical Hamilton-Schrodinger…

Atomic Physics · Physics 2012-05-29 S. V. Prants

We show that two-particle interferences can be used to probe the nuclear motion in a doubly-excited hydrogen molecule. The dissociation of molecular hydrogen by electron impact involves several decay channels, associated to different…

It has been observed that the trajectory of a H2 molecular beam is modified as it passes through a homogeneous magnetic field and an oscillating magnetic field. Based on this observation, this work describes a new method to determine the…

Atomic and Molecular Clusters · Physics 2014-02-04 C. Montero , J. Garcia Urena , M. Dorado

The hydrogen ionization and dissociation front around an ultraviolet radiation source should merge when the ratio of ionizing photon flux to gas density is sufficiently low and the spectrum is sufficiently hard. This regime is particularly…

Astrophysics · Physics 2009-11-13 William J. Henney , R. J. R. Williams , Gary J. Ferland , Gargi Shaw , C. R. O'Dell
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