OLYMPIA-LILBID: A New Laboratory Setup to Calibrate Spaceborne Hypervelocity Ice Grain Detectors Using High-Resolution Mass Spectrometry.

The coupling of an Orbitrap-based mass analyzer to the laser-induced liquid beam ion desorption (LILBID) technique has been investigated, with the aim to reproduce the mass spectra recorded by Cassini's Cosmic Dust Analyzer (CDA) in the vicinity of Saturn's icy moon Enceladus. LILBID setups are usually coupled with time-of-flight (TOF) mass analyzers, with a limited mass resolution (∼800 m/Δm). Thanks to the Orbitrap technology, we developed a unique analytical setup that is able to simulate hypervelocity ice grains' impact in the laboratory (at speeds in the range of 15-18 km/s) with an unprecedented high mass resolution of up to 150 000 m/Δm (at m/z 19 for a 500 ms signal duration). The results will be implemented in the LILBID database and will be useful for the calibration and future data interpretation of the Europa Clipper's SUrface Dust Analyzer (SUDA), which will characterize the habitability of Jupiter's icy moon Europa.

The reaction of C5N- with acetylene as a possible intermediate step to produce large anions in Titan's ionosphere.

A theoretical and experimental investigation of the reaction C5N- + C2H2 has been carried out. This reaction is of astrophysical interest since the growth mechanism of large anions that have been detected in Titan's upper atmosphere by the Cassini plasma spectrometer are still largely unknown. The experimental studies have been performed using a tandem quadrupole mass spectrometer which allows identification of the different reaction channels and assessment of their reaction thresholds. Results of these investigations were compared with the predictions of ab initio calculations, which identified possible pathways leading to the observed products and their thermodynamical properties. These computations yielded that the majority of these products are only accessible via energy barriers situated more than 1 eV above the reactant energies. In many cases, the thresholds predicted by the ab initio calculations are in good agreement with the experimentally observed ones. For example, the chain elongation reaction leading to C7N-, although being slightly exoergic, possesses an energy barrier of 1.91 eV. Therefore, the title reaction can be regarded to be somewhat unlikely to be responsible for the formation of large anions in cold environments such as interstellar medium or planetary ionospheres.

Selected ion flow tube study of the reactions of H3 O+ and NO+ with a series of primary alcohols in the presence of water vapour in support of selected ion flow tube mass spectrometry.

RATIONALE: Alcohols are often present in foods and other biological media, including exhaled breath, urine and cell culture headspace. For their analysis by selected ion flow tube mass spectrometry (SIFT-MS), the ion chemistry initiated by the reactions of the reagent ions H3 O+ and NO+ with alcohol molecules in the presence of water molecules needs to be understood and quantitatively described. METHODS: The reactions of H3 O+ and NO+ ions have been studied with the primary alcohols, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol and 1-hexanol, under the conditions used for SIFT-MS analyses (1 Torr He; 0.1 Torr air sample; 300 K) and over a range of sample gas humidity from 1% to 5.5%. RESULTS: The H3 O+ reactions led to the formation of protonated alcohol molecules MH+ and their hydrates MH+ (H2 O)1,2,3 and (MH+ -H2 O) fragment ions. The NO+ reactions were observed to proceed mainly via hydride ion transfer, resulting in the formation of [M-H]+ product ions. Formation of the NO+ M adduct ions was also observed due to ligand switching between the NO+ (H2 O)1,2 hydrated reagent ions and M, and via direct NO+ /M association in the case of ethanol. The variation in the percentages of the hydrated product ions with the air sample humidity is reported. CONCLUSIONS: This detailed study has provided the kinetics data, including the secondary hydrated ion product distributions, for the reactions of a number of volatile primary alcohols with the SIFT-MS reagent ions H3 O+ and NO+ , which allows their analyses by SIFT-MS in humid air and also helps in the interpretation of proton transfer reaction (PTR)-MS data. Copyright © 2016 John Wiley & Sons, Ltd.

Is the Reaction of C3N(-) with C2H2 a Possible Process for Chain Elongation in Titan's Ionosphere?

The reaction of C3N(-) with acetylene was studied using three different experimental setups, a triple quadrupole mass spectrometer (Trento), a tandem quadrupole mass spectrometer (Prague), and the "CERISES" guided ion beam apparatus at Orsay. The process is of astrophysical interest because it can function as a chain elongation mechanism to produce larger anions that have been detected in Titan's ionosphere by the Cassini Plasma Spectrometer. Three major products of primary processes, C2H(-), CN(-), and C5N(-), have been identified, whereby the production of the cyanide anion is probably partly due to collisional induced dissociation. The formations of all these products show considerable reaction thresholds and also display comparatively small cross sections. Also, no strong signals of anionic products for collision energies lower than 1 eV have been observed. Ab initio calculations have been performed to identify possible pathways leading to the observed products of the title reaction and to elucidate the thermodynamics of these processes. Although the productions of CN(-) and C5N(-) are exoergic, all reaction pathways have considerable barriers. Overall, the results of these computations are in agreement with the observed reaction thresholds. Due to the existence of considerable reaction energy barriers and the small observed cross sections, the title reaction is not very likely to play a major role in the buildup of large anions in cold environments like the interstellar medium or planetary and satellite ionospheres.

A Pilot Study of Ion - Molecule Reactions at Temperatures Relevant to the Atmosphere of Titan.

Reliable theoretical models of the chemical kinetics of the ionosphere of Saturn's moon, Titan, is highly dependent on the precision of the rates of the reactions of ambient ions with hydrocarbon molecules at relevant temperatures. A Variable Temperature Selected Ions Flow Tube technique, which has been developed primarily to study these reactions at temperatures within the range of 200-330 K, is briefly described. The flow tube temperature regulation system and the thermalisation of ions are also discussed. Preliminary studies of two reactions have been carried out to check the reliability and efficacy of kinetics measurements: (i) Rate constants of the reaction of CH3+ ions with molecular oxygen were measured at different temperatures, which indicate values in agreement with previous ion cyclotron resonance measurements ostensibly made at 300 K. (ii) Formation of CH3+ ions in the reaction of N2+ ions with CH4 molecules were studied at temperatures within the range 240-310 K which showed a small but statistically significant decrease of the ratio of product CH3+ ions to reactant N2+ ions with reaction temperature.

H/D exchange in reactions of OH(-) with D2 and of OD(-) with H2 at low temperatures.

Using a cryogenic linear 22-pole rf ion trap, rate coefficients for H/D exchange reactions of OH(-) with D2 (1) and OD(-) with H2 (2) have been measured at temperatures between 11 K and 300 K with normal hydrogen. Below 60 K, we obtained k1 = 5.5 × 10(-10) cm(3) s(-1) for the exoergic . Upon increasing the temperature above 60 K, the data decrease with a power law, k1(T) ∼T(-2.7), reaching ≈1 × 10(-10) cm(3) s(-1) at 200 K. This observation is tentatively explained with a decrease of the lifetime of the intermediate complex as well as with the assumption that scrambling of the three hydrogen atoms is restricted by the topology of the potential energy surface. The rate coefficient for the endoergic increases with temperature from 12 K up to 300 K, following the Arrhenius equation, k2 = 7.5 × 10(-11) exp(-92 K/T) cm(3) s(-1) over two orders of magnitude. The fitted activation energy, EA-Exp = 7.9 meV, is in perfect accordance with the endothermicity of 24.0 meV, if one accounts for the thermal population of the rotational states of both reactants. The low mean activation energy in comparison with the enthalpy change in the reaction is mainly due to the rotational energy of 14.7 meV contributed by ortho-H2 (J = 1). Nonetheless, one should not ignore the reactivity of pure para-H2 because, according to our model, it already reaches 43% of that of ortho-H2 at 100 K.

Stabilization of H+-H2 collision complexes between 11 and 28 K.

Formation of H(3)(+) via association of H(+) with H(2) has been studied at low temperatures using a 22-pole radiofrequency trap. Operating at hydrogen number densities from 10(11) to 10(14) cm(-3), the contributions of radiative, k(r), and ternary, k(3), association have been extracted from the measured apparent binary rate coefficients, k*=k(r)+k(3)[H(2)]. Surprisingly, k(3) is constant between 11 and 22 K, (2.6±0.8)×10(-29) cm(6) s(-1), while radiative association decreases from k(r)(11 K)=(1.6±0.3)×10(-16) cm(3) s(-1) to k(r)(28 K)=(5±2)×10(-17) cm(3) s(-1). These results are in conflict with simple association models in which formation and stabilization of the complex are treated separately. Tentative explanations are based on the fact that, at low temperatures, only few partial waves contribute to the formation of the collision complex and that ternary association with H(2) may be quite inefficient because of the 'shared proton' structure of H(5)(+).