Papers by Stefano Falcinelli
Physical Chemistry Chemical Physics, 2023
The present perspective review focuses on the role of the precursor state, controlling the dynami... more The present perspective review focuses on the role of the precursor state, controlling the dynamical evolution of elementary processes, whose structure and stability are often difficult to characterize on quantitative grounds. In particular, such a state depends on the critical balance of weak intermolecular forces operative at long and intermediate separation distances. In this paper, a complementary problem has been properly addressed, concerning the suitable formulation of the intermolecular forces involved, defined in terms of a limited number of parameters and applicable in the whole space of the relative configurations of interacting partners. Important help to the solution of such a problem has been provided by the phenomenological method which adopts semi-empirical and empirical formulas to represent the basic features of the leading interaction components. Such formulas are defined in terms of a few parameters directly or indirectly related to the fundamental physical properties of the interacting partners. In this way, the basic features of the precursor state controlling its stability and its dynamical evolution have been defined in an internally consistent way for several elementary processes, having apparently different natures. Particular attention has been paid to the chemi-ionization reactions: they are treated as prototype oxidation processes for which all electronic rearrangements affecting stability and evolution of the precursor state, coincident with the reaction transition state, have been characterized in great detail. The obtained information appears to be in the perspective of general interest for many other elementary processes, difficult to investigate in the same detail since many other effects mask their basic features.
Frontiers in Chemistry, May 14, 2019
Bioalcohols are a promising family of biofuels. Among them, 1-butanol has a strong potential as a... more Bioalcohols are a promising family of biofuels. Among them, 1-butanol has a strong potential as a substitute for petrol. In this manuscript, we report on a theoretical and experimental characterization of 1-butanol thermal decomposition, a very important process in the 1-butanol combustion at high temperatures. Advantage has been taken of a flash pyrolysis experimental setup with mass spectrometric detection, in which the brief residence time of the pyrolyzing mixture inside a short, resistively heated SiC tube allows the identification of the primary products of the decomposing species, limiting secondary processes. Dedicated electronic structure calculations of the relevant potential energy surface have also been performed and RRKM estimates of the rate coefficients and product branching ratios up to 2,000 K are provided. Both electronic structure and RRKM calculations are in line with previous determinations. According to the present study, the H 2 O elimination channel leading to 1-butene is more important than previously believed. In addition to that, we provide experimental evidence that butanal formation by H 2 elimination is not a primary decomposition route. Finally, we have experimental evidence of a small yield of the CH 3 elimination channel.
Experimental and theoretical studies of atomic oxygen reactions with terminal alkenes: Relevance of the formaldehyde product channel for atmospheric organic aerosol growth
Rendiconti lincei. Scienze fisiche e naturali, Jan 31, 2018
The focus of the present work is on the detailed characterization of the most relevant components... more The focus of the present work is on the detailed characterization of the most relevant components of the intermolecular interaction, which determine anisotropic force fields driving the molecular dynamics under a variety of conditions. This target is here achieved by combining in a unifying picture the results of different type of experiments, probing complementary aspects of the intermolecular interactions involved. In particular, the analysis of high-resolution scattering data led to an accurate evaluation of the strength and anisotropy of non-covalent interaction components, due to the balance of size (or Pauli) repulsion with dispersion and induction attraction, to which electrostatic contributions must be added. Moreover, for the complete representation of the intermolecular interaction other components of covalent (chemical) nature, mostly affected by charge (electron) transfer effects, must be properly taken into account. Particular attention has been recently devoted to some experimental findings probing in detail the strength, range, anisotropy and role of the charge transfer effects. Obtained results have been important to develop suitable analytical representations for the potential energy surfaces (PESs), tested and improved by exploiting also the comparison with results of ab initio calculations, useful to provide an internally consistent description of the intermolecular interaction both in the most and less stable configurations of the interacting system. The complete and appropriate formulation of the PESs must be then considered crucial not only to describe the dynamics of elementary processes occurring in interstellar medium and in planetary atmospheres, but also to control equilibrium and non-equilibrium phenomena of applied interest, as those occurring in combustion, flames and plasmas.
Molecular beam scattering experiments probing the interaction of Cl2 with simple molecules (D2, O2, D2O, ND3)
Chemical Physics Letters, May 1, 2021
Abstract Molecular beam experiments for the scattering of D2, O2, D2O, and ND3 by Cl2 have been c... more Abstract Molecular beam experiments for the scattering of D2, O2, D2O, and ND3 by Cl2 have been carried out to probe the involved intermolecular interaction and the quantum “glory” interference effect has been observed for all the systems. Simple and reliable interaction potentials, defined as a combination of an anisotropic van der Waals, polar flattening, charge transfer and electrostatic terms have been obtained.
A theoretical study of formation routes and dimerization of methanimine: implications for the aerosols presence in the upper atmosphere of Titan
Research Square (Research Square), Nov 3, 2022
The detailed characterization of barrier-less chemi-ionization reactions provides unique-direct i... more The detailed characterization of barrier-less chemi-ionization reactions provides unique-direct information on basic quantities determining the topology of their stereo-dynamics. The precursor state, formed by collisions of reagents, plays here an important role being coincident with the reaction transition state. All the features of such a state, as well as its structure and stability, are directly or indirectly controlled by intermolecular forces operative in each collision complex. Particular attention it must be focused on the selectivity of the orbital angular momentum, affecting the fate of each collision event at any collision energy. Moreover, the distance of the closest approach (turning point) of reagents, controls the relative weight of two different reaction mechanisms: i) An exchange mechanism triggered by strong chemical forces that act mainly at short separation distances, inducing an electron transfer between the reactants through a prototype oxidation process; ii) A radiative mechanism, caused by the combination of weak chemical and physical forces dominant at larger distances and which provokes an electron ejection via a pure photoionization event determined by the exchange of a "virtual" photon between the reacting partners. Obtained results are of great interest for many other elementary processes, difficult to characterize at the same level of detail. They suggest some limitations of the so called "capture models", usually exploited to describe many other barrier-less processes, like ion-molecule reactions, occurring in interstellar medium, planetary atmospheres and plasmas.
Calcoli di struttura elettronica e RRKM sulla reazione CH3OH2+ + CH3OH
Molecules
The behavior of nitrosyl chloride (ClNO) exposed to ionizing radiation was studied by direct prob... more The behavior of nitrosyl chloride (ClNO) exposed to ionizing radiation was studied by direct probing valence-shell electrons in temporal coincidence with ions originating from the fragmentation process of the transient ClNO2+. Such a molecular dication was produced by double photoionization with synchrotron radiation in the 24–70 eV photon energy range. The experiment has been conducted at the Elettra Synchrotron Facility of Basovizza (Trieste, Italy) using a light beam linearly polarized with the direction of the polarization vector parallel to the ClNO molecular beam axis. ClNO molecules crossing the photon beam at right angles in the scattering region are generated by effusive expansion and randomly oriented. The threshold energy for the double ionization of ClNO (30.1 ± 0.1 eV) and six dissociation channels producing NO+/Cl+, N+/Cl+, N+/O+, O+/Cl+, ClN+/O+, NO+/Cl2+ ion pairs, with their relative abundance and threshold energies, have been measured.
The European Physical Journal D
This paper reports on the characterization of the stereo-dynamic controlling three different chem... more This paper reports on the characterization of the stereo-dynamic controlling three different chemi-ionization reactions, recent objective of our study, since they participate to the balance of phenomena occurring in plasma, interstellar medium, planetary atmospheres, flames and lasers. The optical potential, obtained by a phenomenological method and defined in the whole space of the relative configurations of reagents, has been formulated in an accurate and internally consistent way for three different systems. Some cuts of the multidimensional potential, that asymptotically correlate with a specific fine level of the open shell atom and/or with a defined orientation of the molecular reagent, have been exploited in the present study to emphasize crucial features of the collision dynamics along selected entrance channels of the reactions. Consistently, basic quantities determining the topology of the reaction stereo-dynamics have been properly defined, emphasizing in the three cases ...
The detailed characterization of barrier-less chemi-ionization reactions provides unique-direct i... more The detailed characterization of barrier-less chemi-ionization reactions provides unique-direct information on basic quantities determining the topology of their stereo-dynamics. The precursor state, formed by collisions of reagents, plays here an important role being coincident with the reaction transition state. All the features of such a state, as well as its structure and stability, are directly or indirectly controlled by intermolecular forces operative in each collision complex. Particular attention it must be focused on the selectivity of the orbital angular momentum, affecting the fate of each collision event at any collision energy. Moreover, the distance of the closest approach (turning point) of reagents, controls the relative weight of two different reaction mechanisms: i) An exchange mechanism triggered by strong chemical forces that act mainly at short separation distances, inducing an electron transfer between the reactants through a prototype oxidation process; ii) A...
Stereo-Dynamics of Autoionization Reactions Induced by Ne*(3P0,2) Metastable Atoms with HCl and HBr Molecules: Experimental and Theoretical Study of the Reactivity Through Selective Collisional Angular Cones
Lecture Notes in Computer Science, 2022
A Comparative Study of the Ba+HI and Ba+DI Reactions
1995 Conference on the Dynamics of Molecular Collisions, 1995
In this paper we illustrate the Free-methane (Fuel from RenewablE Energies – methane) proposal su... more In this paper we illustrate the Free-methane (Fuel from RenewablE Energies – methane) proposal submitted to the Horizon 2020 Call H2020-LCE-2016-2017 (COMPETITIVE LOW-CARBON ENERGY) as a Research and Innovation Action (Proposal number: 763936-1) for the first step of a two-stage process. The project is aimed at building a solid background for the assembling of a novel apparatus using renewable energies to produce carbon neutral fuels through a chemical catalytic conversion of carbon dioxide waste flue gases. The first operational line of the proposal is the theoretical, computational and experimental treatment of elementary reactive and non-reactive molecular processes on which the project is grounded. The second operational line of the proposal is the designing and fabricating the technological components of the proposed apparatus. The project will lead to the production of three basic innovative components of the apparatus: a new electrolyser and two highly efficient reactors prod...
Coulomb explosion of molecular dications and escape of fragment ions from planetary atmospheres
Radiochimica Ambientale - Una Guida Pratica Per Capire Che Cos’È e Come Si Misura
The Journal of Chemical Physics, 2021
The interactions of He and Ne with propylene oxide have been investigated with the molecular beam... more The interactions of He and Ne with propylene oxide have been investigated with the molecular beam technique by measuring the total (elastic + inelastic) integral cross section as a function of collision velocity. Starting from the analysis of these experimental data, potential energy surfaces, formulated as a function of the separation distance and orientation of propylene oxide with respect to the interacting partners, have been built: The average depth of potential wells (located at intermediate separation distances) has been characterized by analyzing the observed “glory” quantum effects, and the strength of long-range attractions has been obtained from the magnitude and the velocity dependence of the smooth component of measured cross sections. The surfaces, tested and improved against new ab initio calculations of minima interaction energies at the complete basis set level of theory, are defined in the full space of relative configurations. This represents a crucial condition t...
The atmosphere of Titan, the largest moon of Saturn, is believed to be in some way reminiscent of... more The atmosphere of Titan, the largest moon of Saturn, is believed to be in some way reminiscent of the primordial atmosphere of Earth, being composed mainly by dinitrogen, methane, simple nitriles like HCN and HCCCN, simple hydrocarbons like C2H6, C2H4 and C2H2, H2 and Ar. Dinitrogen is the prevalent species, being the 97% of the atmosphere and the second relevant constituent is CH4 which represents an average amount of 2.7%. All the other species are present only in trace amounts, but their reactivity is very important as suggested by the plethora of information provided by the NASA/ESA/ASI Cassini-Huygens mission. Recent investigations suggested also the presence of positive ions and negatively charged ions in Titan’s ionosphere. More recent information were provided by the observations performed with the ALMA interferometer. Among the species identified by Cassini Ion Neutral Spectrometer (INMS), benzene shows a relatively important mole fraction, being 1.3’10-6 at 950 km. However...
Determination of Volatile Aroma Composition Profiles of Coco de Mèr (Lodoicea Maldivica) Fruit: Analytical Study by HS-SPME and GC/MS Techniques
This work reports the detection and identification of volatile chemical compounds in fruit kernel... more This work reports the detection and identification of volatile chemical compounds in fruit kernel of “Lodoicea maldivica” coco nucifera palm by gas chromatographic method. The analysis was performed by HS-SPME and GC/MS techniques to determine volatile aroma composition profiles in internal and external pulp. No qualitative differences in flavor composition were observed between two pulp parts, but there were notable variations in the abundance levels of the prominent compounds. Computational method was used to extract individual component mass spectra from GC/MS data files by using the AMDIS version 2.65 software. With such a procedure we are able to construct our own mass spectra library determining retention indices for chemical compounds of our interest in the used specific experimental conditions.
Analytical Study of Lodoicea Maldivica Fruits by GC-MS Technique
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Papers by Stefano Falcinelli