Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes

It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani-ons are emitted with low kinetic energy due to many-body processes. Model calcu-lations show that both nucleus-nucleus interactions and electronic excitations con-tribute to the observed large anion emission yield.Comment: 5 pages, 4 figure

Anion and cation emission from water molecules after collisions with 6.6-keV 16 O+ ions

DOI: https://doi.org/10.1103/PhysRevA.100.032713arXiv link: http://arxiv.org/abs/1910.00657International audienceAnion and cation emission following water dissociation was studied for 6.6-keV $^{16}$O$^{+}$ + H$_{2}$O collisions. Absolute cross sections for the emission of all positively and negatively charged fragments, differential in both energy and observation angle, were measured. The fragments formed in hard, binary collisions appearing in peaks were distinguishable from those created in soft collisions with many-body dynamics that result in a broad energy spectrum. A striking feature is that anions and cations are emitted with similar energy and angular distributions, with a nearly constant ratio of about 1:100 for H$^{-}$ to H$^{+}$. Model calculations were performed at different levels of complexity. Four-body scattering simulations reproduce the measured fragment distributions if adequate kinetic-energy release of the target is taken into account. Providing even further insight into the underlying processes, predictions of a thermodynamic model indicate that transfer ionization at small impact parameters is the dominant mechanism for H$^{+}$ creation. The present findings confirm our earlier observation that in molecular fragmentation induced by slow, singly charged ions, the charge states of the emitted hydrogen fragments follow a simple statistical distribution independent of the way they are formed

A systematic IR and VUV spectroscopic investigation of ion, electron, and thermally processed ethanolamine ice

The recent detection of ethanolamine (EtA, HOCH2CH2NH2), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (H2O) ice, to electron, ion, and thermal processing, representing ‘energetic’ mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of H2O:EtA mixed ice obtained after 1 MeV He+ ion irradiation have been collected at different doses. The main radiolysis products, including H2O, CO, CO2, NH3, and CH3OH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He+ ion irradiation of pure EtA and H2O:EtA mixed ice are derived to range between 10.8 − 26.3 eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in H2O ice is more stable than in pure form and it should survive throughout the star and planet formation process

Transmission of

Experiments were carried out to study the transmission of $$3\hbox {-keV Ne}^{7+}$$ ions through nanocapillaries in polyethylene terephthalate (PET). The capillaries were highly parallel with a diameter of 230 nm and a length of $$12\, \mu \hbox {m}$$. The transmission during the charging and discharging processes was measured for different tilt angles ranging from $$3^{\circ }$$ to $$9^{\circ }$$. An advanced instrumental technique was employed to avoid recharging effects during the discharging process. During discharging, the decay of the guided transmission is found to be non-exponential depending strongly on the tilt angle. The experiments were interpreted by model calculations using a minimum number of free parameters. The discharging results for different tilt angles are reproduced by a single decay function involving nonlinear properties. After measuring the discharge for nearly 7 hours, the charge depletion rate was found to be unexpectedly small resulting in a long duration of the charges in the capillary

Two- and many-body effects in cation emission from H 2 O molecules by O + impact at keV energies: Similarities between ionization of atoms and proton emission from molecules

International audienc

Formation of anions and cations via a binary-encounter process in OH+ + Ar collisions: The role of dissociative excitation and statistical aspects

Molecular fragmentation leading to the formation of negatively and positively charged hydrogen ions in 7-keV OH+ + Ar collisions is investigated experimentally. The most striking finding is that negative and positive hydrogen ions are emitted with very similar angular dependences. Also, the kinetic energy distribution of the H+ fragment shows strong similarities with that of the ejected H- ion. The kinematics of the emitted H core is found to be essentially driven by its scattering on the atomic target. However, in addition to this binary-encounter process, dissociative electronic excitation of the molecular projectile has to be invoked to explain the observed fragmentation patterns. Though the electron capture process is complex, it is shown that the relative population of the different final charge states of the outgoing fragments can be described by simple statistical laws

Scar dechanneling: new method for scar-related left ventricular tachycardia substrate ablation

Item does not contain fulltextBACKGROUND: Ventricular tachycardia (VT) substrate ablation usually requires extensive ablation. Scar dechanneling technique may limit the extent of ablation needed. METHODS AND RESULTS: The study included 101 consecutive patients with left ventricular scar-related VT (75 ischemic patients; left ventricular ejection fraction, 36 +/- 13%). Procedural end point was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance followed by abolition of residual inducible VTs. By itself, scar dechanneling rendered noninducibility in 54.5% of patients; ablation of residual inducible VT increased noninducibility to 78.2%. Patients needing only scar dechanneling had a shorter procedure (213 +/- 64 versus 244 +/- 71 minutes; P = 0.027), fewer radiofrequency applications (19 +/- 11% versus 27 +/- 18%; P = 0.01), and external cardioversion/defibrillation shocks (20% versus 65.2%; P < 0.001). At 2 years, patients needing scar dechanneling alone had better event-free survival (80% versus 62%) and lower mortality (5% versus 11%). Incomplete CC-electrogram elimination was the only independent predictor (hazard ratio, 2.54 [1.06-6.10]) for the primary end point. Higher end point-free survival rates were observed in patients noninducible after scar dechanneling (log-rank P = 0.013) and those with complete CC-electrogram elimination (log-rank P = 0.013). The complications rate was 6.9%, with no deaths. CONCLUSIONS: Scar dechanneling alone results in low recurrence and mortality rates in more than half of patients despite the limited ablation extent required. Residual inducible VT ablation improves acute results, but patients who require it have worse outcomes. Recurrences are mainly related to incomplete CC-electrogram elimination

Anion emission from H 2 O molecules colliding with positive O + ions at keVenergies: the role of dissociative excitation

International audienc

Comparison between anion and cation emission from CH 4 molecules colliding with 10.5-keV C + ions: fragment-energy aspects

International audienc