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

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

A theoretical investigation of the reaction between the amidogen, NH, and the ethyl, C2H5, radicals: a possible gas-phase formation route of interstellar and planetary ethanimine

The reaction between the amidogen, NH, radical and the ethyl, C2H5, radical has been investigated by performing electronic structure calculations of the underlying doublet potential energy surface. Rate coefficients and product branching ratios have also been estimated by combining capture and RRKM calculations. According to our results, the reaction is very fast, close to the gas-kinetics limit. However, the main product channel, with a yield of ca. 86-88% in the range of temperatures investigated, is the one leading to methanimine and the methyl radical. The channels leading to the two E-, Z- stereoisomers of ethanimine account only for ca. 5-7% each. The resulting ratio [E-CH3CHNH]/[Z-CH3CHNH] is ca. 1.2, that is a value rather lower than that determined in the Green Bank Telescope PRIMOS radio astronomy survey spectra of Sagittarius B2 North (ca. 3). Considering that ice chemistry would produce essentially only the most stable isomer, a possible conclusion is that the observed [E-CH3CHNH]/[Z-CH3CHNH] ratio is compatible with a combination of gas-phase and grain chemistry. More observational and laboratory data are needed to definitely address this issue

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

Interstellar dimethyl ether gas-phase formation: a quantum chemistry and kinetics study

Dimethyl ether is one of the most abundant interstellar complex organic molecules. Yet its formation route remains elusive. In this work, we have performed electronic structure and kinetics calculations to derive the rate coefficients for two ion-molecule reactions recently proposed as a gas-phase formation route of dimethyl ether in interstellar objects, namely CH$_3$OH + CH$_3$OH$_2^+$ $\rightarrow$ (CH$_3$)$_2$OH$^+$ + H$_2$O followed by (CH$_3$)$_2$OH$^+$ + NH$_3$ $\rightarrow$ CH$_3$OCH$_3$ + NH$_4^+$. A comparison with previous experimental rate coefficients for the reaction CH$_3$OH + CH$_3$OH$_2^+$ sustains the accuracy of the present calculations and allow a more reliable extrapolation at the low temperatures of interest in interstellar objects (10-100 K). The rate coefficient for the reaction (CH$_3$)$_2$OH$^+$ + NH$_3$ is, instead, provided for the first time ever. The rate coefficients derived in this work essentially confirm the prediction by Taquet et al. (2016) concerning dimethyl ether formation in hot cores/corinos. Nevertheless, this formation route cannot be efficient in cold objects (like prestellar cores) where dimethyl ether is also detected, because ammonia has a very low abundance in those environments

Introduzione

Il I Convegno nazionale del Laboratorio Permanente di Diritto Penale, tenutosi a Perugia il 19 settembre 2014, ha proposto alla comunit\ue0 scientifica un incontro di studio sul tema \u201cLa giustizia penale nella rete. Le nuove sfide della societ\ue0 dell\u2019informazione nell\u2019epoca di Internet\u201d. Il riscontro si \ue8 espresso attraverso un vivace dibattito sui temi pi\uf9 attuali che coinvolgono le complesse implicazioni fra il sistema penale e le nuove tecnologie: la societ\ue0 dell\u2019informazione, infatti, caratterizzata dall\u2019esplosione di Internet e dei nuovi prodotti tecnologici, ha da tempo comportato dei cambiamenti epocali in ogni settore della vita umana, implicanti non solo molteplici opportunit\ue0 di sviluppo \u201cpositivo\u201d, sul piano sociale, culturale ed economico. Su questo fertile terreno fioriscono difatti anche nuovi fenomeni, modi e tipi di comportamenti di rilievo penale, e si aprono \u201caltri\u201d percorsi per commettere reati \u201ctradizionali\u201d; d\u2019altro canto il mondo digitale si dimostra una fondamentale frontiera per la lotta alla criminalit\ue0 moderna, offrendo innovativi strumenti e mezzi per la ricerca delle prove e, in generale, per il contrasto a vasti settori di illiceit\ue0 penale

La giustizia penale nella \u201crete\u201d. Le nuove sfide della societ\ue0 dell\u2019informazione nell\u2019epoca di Internet

Il volume raccoglie gli atti del I convegno nazionale del Laboratorio Permanente di Diritto Penale, che si \ue8 tenuto a Perugia il 19 settembre 2014, sul tema \u201cLa giustizia penale nella rete. Le nuove sfide della societ\ue0 dell\u2019informazione nell\u2019epoca di Internet\u201d. L\u2019incontro \ue8 stato caratterizzato da un vivace dibattito sui temi pi\uf9 attuali che coinvolgono le complesse implicazioni fra il sistema penale e le nuove tecnologie in una prospettiva europea ed internazionale: la societ\ue0 dell\u2019informazione, infatti, ha da tempo comportato dei cambiamenti epocali in ogni settore della vita umana, implicanti non solo molteplici opportunit\ue0 di sviluppo \u201cpositivo\u201d, sul piano sociale, culturale ed economico. Su questo fertile terreno fioriscono difatti anche nuovi fenomeni, modi e tipi di comportamenti di rilievo penale, e si aprono \u201caltri\u201d percorsi per commettere reati \u201ctradizionali\u201d; d\u2019altro canto il mondo digitale si dimostra una fondamentale frontiera per la lotta alla criminalit\ue0 moderna, offrendo innovativi strumenti e mezzi per la ricerca delle prove e, in generale, per il contrasto a vasti settori di illiceit\ue0 penale

Double photoionization of propylene oxide: a coincidence study of the ejection of a pair of valence-shell electrons

Propylene oxide, a favorite target of experimental and theoretical studies of circular dichroism, was recently discovered in interstellar space, further amplifying the attention to its role in the current debate on protobiological homochirality. In the present work, a photoelectron-photoion-photoion coincidence technique, using an ion-imaging detector and tunable synchrotron radiation in the 18.0-37.0 eV energy range, permits us (i) to observe six double ionization fragmentation channels, their relative yields being accounted for about two-thirds by the couple (C2H4+, CH2O+) and one-fifth by (C2H3+, CH3O+); (ii) to measure thresholds for their openings as a function of photon energy; and (iii) to unravel a pronounced bimodality for a kinetic-energy-released distribution, fingerprint of competitive non-adiabatic mechanisms

Molecular Fragmentation of Acetylene by VUV Double Photoionization

Acetylene is a simple molecule of interest for interstellar medium (ISM) and planetary atmospheres. The presence of C2H2 was detected by IR spectroscopic measurements. Acetylene was also found as a minor component in the atmosphere of gas giants like the planet Jupiter, in the atmosphere of Saturn's satellite Titan, and in comets, where photochemical experiments have demonstrated that this simple hydrocarbon is a likely precursor of C2, a widely observed component in such environments. It has to be noted that the presence in planetary atmospheres and ISM of Vacuum Ultra Violet (VUV) light's photons as well as cosmic rays makes highly probable the double photoionization of molecular species with the production of molecular dications producing subsequent dissociation into ionic fragments having a high kinetic energy content of several eV. This translational energy is sufficient in some cases to allow ions escape from the upper atmosphere of some planet of the Solar System, as Venus, Mars and Titan, into space. In this contribution we present the experimental study of the microscopic dynamics of the two-body dissociation reactions of the C2H2+2 dication, induced by the double ionization of acetylene molecules by VUV photons in the energy range of 31.9–50.0 eV. The photoionizing agent was a tunable synchrotron radiation beam, while ion products are revealed by coupling photoelectron-photoion-photoion-coincidence and ion imaging techniques. The measured angular distributions and kinetic energy of product ions exhibit significant changes (as the photon energy increases) for the three leading dissociation reactions producing H++C2H+, C++CH2+, and CH++CH+, providing detailed information on the fragmentation dynamics of the C2H22+ dication

Phenolic content and antioxidant activity of einkorn and emmer sprouts and wheatgrass obtained under different radiation wavelengths

Abstract Sprouted seeds represent intriguing ready-to-eat micro-scale vegetables for the healthy food market, since they are tasty and rich in bioactive compounds. However, sprouts have been recently proposed as a source for the extraction and purification of several phytochemicals to be used in food supplementation or pharmaceutics. Recently, there has been an industrialization of sprout production, carried out indoor, often with use of artificial light, which have implications on biomass yield and composition, and on energetic and economic costs. This work investigates the effects of different radiation wavelengths from light emitting diodes (LED) on free and bound phenolics and antioxidant activity of sprouts and wheatgrass of einkorn (Triticum monococcum L. ssp. monococcum) and emmer ([(Triticum turgidum L. spp. dicoccum, (Schrank ex Schubler) Thell.)]). After 3 days of grain incubation in the dark, three light treatments were applied, labelled as BLUE (447 and 470 nm), RED (627 and 655 nm), and SUN (447, 470, 505, 530, 590, 627, 655 nm), for a same total photon flux density (PFD) of 200 μmol m−2 s−1. Sprouts were harvested at 5 days after sowing (DAS) and wheatgrass at 9 DAS. The effect of light was generally not significant for sprouts, much greater and species-specific for wheatgrass: BLUE in einkorn and RED in emmer generally increased free and total content of polyphenol (PC), tannins (TC), flavonoid (FC) and phenolic acids (PAs). The antioxidant activity was increased by BLUE in einkorn and decreased by RED in both species. BLUE and RED resulted energy saving compared to SUN