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Phenylalanine (Phe) is an amino acid that has been identified in carbonaceous meteorites; its formation mechanism in space is unknown, and its radioresistance has been the subject of investigation. This work aims at studying, in the laboratory, the Phe radiolysis by cosmic analogues. The Phe destruction rate, at 300 K, is measured for H, He, and N ion beam irradiation in the 0.5 to 2 kinetic MeV range. Fourier transform infrared (FTIR) spectroscopy was employed to monitor the molecular degradation as a function of fluence. The Phe apparent destruction cross-section

In cold core of dark molecular clouds, where the UV radiation from external sources is strongly attenuated, cosmic rays can induce chemical reactions on the surface of ice-covered grains promoting the ejection of the processed material to the gas phase. We report the positive and negative secondary ion emission from pure CH3CN, C2H3CN, and i-C3H7CN ices due to the bombardment of heavy ions (252Cf fission fragments), simulating the incidence of cosmic rays on to icy surfaces. The secondary ions emitted from each sample were analysed by time-of-flight mass spectrometry, using Plasma Desorption Mass Spectrometry technique. Several ionic species were identified, indicating strong fragmentation on the frozen surface. Proton-transfer processes are suggested to play a role for positive ion desorption, as evidenced by the protonated RCNH+ parent molecules and (RCN)nH+ ionic clusters. The high electron affinity of the cyano radical seems to contribute to the strong emission of CN−, as well as anions attributed to the CHmCN− fragment and (RCN)nCN− cluster series. Sputtering and desorption of ion clusters (positive and negative) induced by heavy ion bombardment are suggested to constitute a route by which new neutral or ionized molecular species may be delivered to the gas phase where thermal desorption is negligible.

Astrophysical ices are exposed to different radiation fields including photons, electrons and ions. The latter stem from interstellar cosmic rays (CR), the solar and stellar winds, shock waves or are trapped in the magnetospheres of giant planets. We briefly discuss the physics of energy deposition by ion ir radiation in condensed matter and experimental methods to study the induced effects. We then present results on radiation effects such as sputtering, amorphisation and compaction, dissociation of molecules, formation of new molecular species after radiolysis and by implantation of ions. The formation and radio-resistance of organic molecules, related to the question of the initial conditions for the emergence of life, are briefly discussed. This review is not meant to be comprehensive, but rather focusses on recent findings, with special emphasis on experiments with heavy multiply charged ion beams. These experiments aim in particular at simulating the effects of CRs on icy grains in dense molecular clouds, and on the formation of molecules on icy bodies in the Solar System.

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Electronic sputtering of organic species being mixed to water ice by residual-gas condensation is analyzed by secondary ion time-of-flight mass spectrometry. The ice samples were prepared at 15 K by deposition from a H2O gas-flow and irradiated by 1.5 MeV N2+ ions while the temperature was raised up to 216 K. Desorption ion yields of positive H2O specific ions as of some organic ion species are measured as a function of temperature. Remarkably high desorption yield variations, mainly of the CnHm ions, were observed during the enrichment of organics hiding the emission of (H2O)nH3O+ cluster ions.

The (NH 3 ) n −1 {NH 3 –H–H 2 O} + cluster series produced by 252 Cf fission fragments (FF) impact onto a NH 3 –H 2 O ice target have been analyzed theoretically and experimentally. The ion desorption yields show a smooth dependence of the cluster population on its mass, with a relative higher abundance for n = 3. Results of DFT calculations show that two main series of cluster ions may be formed corresponding to the {H 3 O} + and {NH 4 H 2 O} + cores. The theoretical analysis shows that the members of the (NH 3 ) n −1 {NH 4 –H 2 O} + series are more stable than those of the (NH 3 ) n {H 3 O} + series, the (NH 3 ) 2 {NH 3 –H–H 2 O} + structure being the most stable one, in agreement with the experiments.

Recent experimental results on positive charged formic acid clusters generated by the impact of (252)Cf fission fragments (FF) on icy formic acid target are examined in this paper by quantum mechanical calculations. Structures for the clusters series, (HCOOH)(n)H(+) and (HCOOH)(n)H(3)O(+), where 2 < or = n < or = 4, are proposed based on ab initio electronic structure methods. Results show that cluster growth does not present a regular pattern of nucleation. A stability analysis was performed considering the commonly defined stability function, where E is the total electronic energy plus the zero point vibrational energy correction, including the BSSE correction. The stability analysis leads to a picture that is compatible with experimental observations, indicating a decay of the stability with the increase of cluster mass. Temporal behavior of the clusters was evaluated by Born-Oppenheimer molecular dynamics to check the mechanism that provides cluster stability. The evaluated temporal profiles indicate the importance of hydrogen atom migration between the formic acid moieties to maintain the stability of the structures.

The structures and abundances of C n = 2 - 16 - clusters produced from amorphous and graphite targets by 337 nm UV laser are analyzed. A systematic search for the more stable conformers at the DFT/B3LYP level of calculation is presented. Two new series and some new structures of previously reported series of negatively charged carbon clusters are proposed: linear (new members), monocyclic (new members), fused ring and non-planar series. The cluster stability analysis indicates higher abundances for the n = 2, 4, 6, 8 and 12 clusters in the negative spectra, in agreement with the experimental observations.

The structures and abundances of C n = 2 – 16 + clusters produced by electronic sputtering from the impact of 252 Cf fission fragments on CO ice and from the UV laser desorption of amorphous carbon and graphite targets are analyzed. A systematic search for the more stable conformers at the DFT/B3LYP level of calculation and their contribution to the mass spectra is reported. A new methodology for a proper taxonomic description of the cluster isomers is proposed. Besides the known linear and monocyclic clusters series, new members of these series and two new series are described: the bi-cyclic and/or tri-cyclic and the rhombic core series.

Hydrocarbon ions are important species in flames, spectroscopy and the interstellar medium. Their importance is reflected in the extensive body of literature on the structure and reactivity of carbocations. However, the geometry, electronic structure and reactivity of carbocations are difficult to assess. This study aims to contribute to the current knowledge of this subject by presenting a quantum mechanics description of methane cation dissociation using multiconfigurational methods. The geometric and electronic parameters of the minimum structure were determined for three main reaction paths: the dissociation CH4(+)→ CH2(+) + H2 and the dissociation-recombination processes CH4(+)↔ CH3(+) + H. The electronic and energetic effects of these reactions were analyzed, and it was found that each reaction path has a strong dependence on the methodology used as well as a strong multiconfigurational character during dissociation. The first doublet excited states are inner-shell excited states and may correspond to the ions that are expected to be formed after electron detachment. The rate coefficient for each reaction path was determined using variational transition state theory and RRKM/master equation calculations. The major dissociation paths, with their rate coefficients at the high-pressure limit, are CH4(+)(X(~)(2)B1) → CH3(+)(A(2)A1') + H((2)S) (k∞(T) = 1.42 × 10(+14) s(-1) exp(-37.12/RT)) and CH4(+)(X(~)(2)B1) → CH2(+)(A(2)A1) + H2((2)Σg(+)) (k∞(T) = 9.18 × 10(+14) s(-1) exp(-55.77/RT)). Our findings help to explain the abundance of ions formed from CH4 in the interstellar medium and to build models of chemical evolution.

Electronic sputtering of lithium fluoride by swift heavy ions was studied as a function of electronic energy loss (dE/dx) e . The single crystal targets were irradiated with swift heavy ion beams (166Z P 692; 46E P /M P (MeV/u) 611). This allowed varying the deposited energy by a factor of 20 (1.86dE/dx (keV/nm) 632). The sputtered secondary ions were measured from well controlled LiF targets without surface contaminations, by means of the time-of-flight technique (TOF-SIMS). The mass spectrum reveals an important contribution of clusters (over single ions), which increases with (dE/dx) e . Another observation for the strongest perturbation at high dE/dx (>8 keV/nm) is that the secondary ion yields saturate: Y(dE/dx) = constant. In contrast, at lower dE/dx (

Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF)n=2,36 neutral clusters suggest that nanotube structures with hexagonal and octagonal transversal cross sections show stability equal to or greater than that of the typical cubic form of large LiF crystals. The nanotube stability was further corroborated by quantum dynamic calculations at room temperature. The fact that stable nanotube structures were also found for other alkali halides (e.g., NaCl and KBr) suggests that this geometry may be widely implemented in material sciences.

We studied the effects produced by the interaction of heavy ion cosmic rays with interstellar and cometary organic molecules in the solid phase. Formic acid (HCOOH) ice at 15 K was irradiated by 267-MeV 56Fe22+ ions and the chemical evolution was analysed using Fourier transform infrared spectroscopy. The destruction cross-section of HCOOH and the formation cross-sections of the produced molecular species have been determined; the sputtering yield values are also discussed. The most abundant chemical species formed by Fe ion irradiation are CO, CO2 and H2O. The half-life of frozen formic acid molecules in the interstellar medium, as a result of interaction with the different cosmic ray constituents, is evaluated to be 108 yr, considering that the destruction cross-section σ d of heavy ions is ruled by a power law as a function of the electronic stopping power Se (i.e. σd ∼ S3/2 e ). Moreover, a complementary study based on mass spectrometry data from the literature has been performed, in order to understand the HCOOH molecule radiolysis, the desorption of its product and the chemical reaction pathways in ice.

Cosmic Rays (CR) have been studied since their discovery by Victor Hess in the years 1911-1913. Interestingly, research in Physics in Brazil started with experiments on CR. Bernhard Gross (INT/Rio), Gleb Wataghin and Giuseppe Occhialini (USP) carried out their investigations on CR in Brazil in the 30's. Franz X. Roser worked with V. Hess (Nobel Prize, 1936) and Cesar Lattes collaborated with Cecil Powell (Nobel Prize, 1950). Nowadays, most of CR research in Brazil is conducted by the Pierre Auger Project. Nevertheless, there is an enormous lack of information on the effects of CR in matter, particularly in organic and biological materials, which motivates measurements of relevant physicochemical data, such as parameters of crystalline structure modifications, sputtering yields and cross sections for inducing associative or dissociative processes of atoms, molecules and molecular fragments. A fascinating question about CR is whether they are/were one of the agents responsible for the transformation of inor...

The most abundant geometries and relative stabilities of alkali halide clusters with a ( XY ) n 0 configuration (e.g., LiF, NaCl, KBr) are described. Five main series were obtained: linear, cyclic, cubic, arc strips and nanotubes. The stability analysis shows that higher members are likely to be formed from the lower member of the same series and/or from two building blocks (n = 1, 2). The energy analysis (D-plot) indicates that the most compact ones (e.g., cubic and nanotubes) present higher stability when compared to the linear, cyclic and arc strip structures; moreover, relative stability between the cubic and nanotube series varies with the cluster size.

An experimental study of the interaction of highly charged, energetic ions (52 MeV (58)Ni(13+) and 15.7 MeV (16)O(5+)) with mixed H(2)O : C(18)O(2) astrophysical ice analogs at two different temperatures is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by cosmic rays inside dense, cold astrophysical environments, such as molecular clouds or protostellar clouds as well at the surface of outer solar system bodies. The measurements were performed at the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France. The gas samples were deposited onto a CsI substrate at 13 K and 80 K. In situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross section at 13 K of both H(2)O and CO(2) is about 3-4 times smaller when O ions are employed. The ice temperature seems to affect differently each species when the same projectile was employed. The formation cross section at 13 K of molecules such as C(18)O, CO (with oxygen from water), and H(2)O(2) increases when Ni ions are employed. The formation of organic compounds seems to be enhanced by the oxygen projectiles and at lower temperatures. In addition, because the organic production at 13 K is at least 4 times higher than the value at 80 K, we also expect that interstellar ices are more organic-rich than the surfaces of outer solar system bodies.

Our groups in Brazil, France and Italy have been active, among others in the world, in performing experiments on physical-chemical effects induced by fast ions colliding with solids (frozen gases, carbonaceous and organic materials, silicates, etc.) of astrophysical interest. The used ions span a very large range of energies, from a few keV to hundreds MeV. Here we present a summary of the results obtained so far on the formation of oxidants (hydrogen peroxide and ozone) after ion irradiation of frozen water, carbon dioxide and their mixtures. Irradiation of pure water ice produces hydrogen peroxide whatever is the used ion and at different temperatures. Irradiation of carbon dioxide and water frozen mixtures result in the production of molecules among which hydrogen peroxide and ozone. The experimental results are discussed in the light of the relevance they have to support the presence of an energy source for biosphere on Europa and other icy moons in the outer Solar System., This research has been supported by the European COST Action CM0805: The Chemical Cosmos.

Icy grain mantles consist of small molecules containing hydrogen, carbon, oxygen and nitrogen atoms (e.g. H2O, CO, CO2, NH3). Such ices, present in different astrophysical environments (giant planets satellites, comets, dense clouds, and protoplanetary disks), are subjected to irradiation of different energetic particles: UV radiation, ion bombardment (solar and stellar wind as well as galactic cosmic rays), and secondary electrons due to cosmic ray ionization of H2. The interaction of these particles with astrophysical ice analogs has been the object of research over the last decades. However, there is a lack of information on the effects induced by the heavy ion component of cosmic rays in the electronic energy loss regime. The aim of the present work is to simulate of the astrophysical environment where ice mantles are exposed to the heavy ion cosmic ray irradiation.Sample ice films at 13K were irradiated by nickel ions with energies in the 1-10 MeV/u range and analyzed by means of FTIR spectrometry. Nickel ions were used because their energy deposition is similar to that deposited by iron ions, which are particularly abundant cosmic rays amongst the heaviest ones.In this work the effects caused by nickel ions on condensed gases are studied (destruction and production of molecules as well as associated cross sections, sputtering yields) and compared with respective values for light ions and UV photons.

We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV 58Ni13+) with interstellar ammonia-containing (H2O:NH3:CO) ice analog in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed at the heavy ion accelerator GANIL in Caen, France. In-situ analysis have been performed by a Fourier transform infrared spectrometer. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide are determined and the estimated half life for the studied species inside dense molecular clouds is 2-3 × 106 years. The IR spectra of organic residue produced by the radiolysis have revealed, at room temperature, five bands that are tentatively assigned to vibration modes of the zwitterionic glycine (NH3+CH2COO−).

In order to simulate the effects of the heavy ion component of cosmic rays on ices in astrophysical environments, the CO and CO2 ices were irradiated with swift nickel ions in the electronic energy loss regime. The ices were prepared by condensing gas onto a CsI substrate at a temperature of 14 K and analyzed by means of infrared (FTIR) spectroscopy. The physical process of deposition by Ni ions is similar to more important and abundant heavy cosmic rays such as Fe ions. Dissociation of the ice molecules, and formation of new molecules were observed. Also, sputtering (leading to desorption of molecules from the solid surface to the gas phase) was observed. It was found that the sputtering yield due to heavy ions cannot be neglected with respect to desorption induced by weakly ionizing particles such as UV photons and protons.