Measurements of ionization cross sections by molecular beam experiments: information content on the imaginary part of the optical potential

In this work, we present and analyze in detail new and recent ionization cross section and mass spectrum determinations, collected in the case of He*, Ne*-H2O, -H2S, and -NH3 ionizing collisions. These sets of data, obtained under the same experimental conditions, are relevant to identify differences in the autoionization stereodynamics of the three hydrogenated molecules and on the selective role of the imaginary part of the optical potential. We demonstrate that in these autoionization processes hydrogen and halogen bonds are competing because they are controlling both real and imaginary components of the optical potential that drives the complete reaction dynamics. In particular, we found that both components critically depend on the angular and radial approach between the reagent partners in determining the collision dynamics

The Possible Role of Penning Ionization Processes in Planetary Atmospheres

In this paper we suggest Penning ionization as an important route of formation for ionic species in upper planetary atmospheres. Our goal is to provide relevant tools to researchers working on kinetic models of atmospheric interest, in order to include Penning ionizations in their calculations as fast processes promoting reactions that cannot be neglected. Ions are extremely important for the transmission of radio and satellite signals, and they govern the chemistry of planetary ionospheres. Molecular ions have also been detected in comet tails. In this paper recent experimental results concerning production of simple ionic species of atmospheric interest are presented and discussed. Such results concern the formation of free ions in collisional ionization of H2O, H2S, and NH3 induced by highly excited species (Penning ionization) as metastable noble gas atoms. The effect of Penning ionization still has not been considered in the modeling of terrestrial and extraterrestrial objects so far, even, though metastable helium is formed by radiative recombination of He+ ions with electrons. Because helium is the second most abundant element of the universe, Penning ionization of atomic or molecular species by He*(23S1) is plausibly an active route of ionization in relatively dense environments exposed to cosmic rays

General treatment for stereo-dynamics of state-to-state chemi-ionization reactions

The microscopic evolution of elementary chemical reactions remains challenging to describe, as a plethora of parallel channels often determines reaction dynamics. Here the authors propose a theoretical approach to formulate the optical potential for Ne*(3P2,0) chemi-ionizations as a prototype gas-phase oxidation process

Molecular Physics of Elementary Processes relevant to Hypersonics: atom-molecule, molecule-molecule and atom-surface processes.

In the present chapter some prototype gas and gas-surface processes occurring within the hypersonic flow layer surrounding spacecrafts at planetary entry are discussed. The discussion is based on microscopic dynamical calculations of the detailed cross sections and rate coefficients performed using classical mechanics treatments for atoms, molecules and surfaces. Such treatment allows the evaluation of the efficiency of thermal processes (both at equilibrium and nonequilibrium distributions) based on state-to-state and state specific calculations properly averaged over the population of the initial states. The dependence of the efficiency of the considered processes on the initial partitioning of energy among the various degrees of freedom is discussed

Interatomic and Intermolecular Coulombic Decay

Interatomic or intermolecular Coulombic decay (ICD) is a nonlocal electronic decay mechanism occurring in weakly bound matter. In an ICD process, energy released by electronic relaxation of an excited atom or molecule leads to ionization of a neighboring one via Coulombic electron interactions. ICD has been predicted theoretically in the mid nineties of the last century, and its existence has been confirmed experimentally approximately ten years later. Since then, a number of fundamental and applied aspects have been studied in this quickly growing field of research. This review provides an introduction to ICD and draws the connection to related energy transfer and ionization processes. The theoretical approaches for the description of ICD as well as the experimental techniques developed and employed for its investigation are described. The existing body of literature on experimental and theoretical studies of ICD processes in different atomic and molecular systems is reviewed. © 2020 American Chemical Societ

Full Dimensional Potential Energy Function and Calculation of State-Specific Properties of the CO+N2 Inelastic Processes Within an Open Molecular Science Cloud Perspective

A full dimensional Potential Energy Surface (PES) of the CO + N2 system has been generated by extending an approach already reported in the literature and applied to N2-N2 (Cappelletti et al., 2008), CO2-CO2 (Bartolomei et al., 2012), and CO2-N2 (Lombardi et al., 2016b) systems. The generation procedure leverages at the same time experimental measurements and high-level ab initio electronic structure calculations. The procedure adopts an analytic formulation of the PES accounting for the dependence of the electrostatic and non-electrostatic components of the intermolecular interaction on the deformation of the monomers. In particular, the CO and N2 molecular multipole moments and electronic polarizabilities, the basic physical properties controlling the behavior at intermediate and long-range distances of the interaction components, were made to depend on relevant internal coordinates. The formulated PES exhibits substantial advantages when used for structural and dynamical calculations. This makes it also well suited for reuse in Open Molecular Science Cloud services

Summaries of FY 1997 Research in the Chemical Sciences

The objective of this program is to expand, through support of basic research, knowledge of various areas of chemistry, physics and chemical engineering with a goal of contributing to new or improved processes for developing and using domestic energy resources in an efficient and environmentally sound manner. Each team of the Division of Chemical Sciences, Fundamental Interactions and Molecular Processes, is divided into programs that cover the various disciplines. Disciplinary areas where research is supported include atomic, molecular, and optical physics; physical, inorganic, and organic chemistry; chemical energy, chemical physics; photochemistry; radiation chemistry; analytical chemistry; separations science; heavy element chemistry; chemical engineering sciences; and advanced battery research. However, traditional disciplinary boundaries should not be considered barriers, and multi-disciplinary efforts are encouraged. In addition, the program supports several major scientific user facilities. The following summaries describe the programs