In the environments where stars and planets form, about one percent of mass is in form micro-meter sized particles known as dust. However small insignificant these dust grains may seem, they are responsible for production simplest (H2) to most complex (amino-acids) molecules observed our Universe. Dust recognized powerful nano-factories that produce chemical species. However, mechanism converts species on gas remains elusive. Here we report experimental evidence forming interstellar analogs...

Mass spectrometry measurements show the formation of highly superhydrogenated derivatives polycyclic aromatic hydrocarbon molecule coronene through H atom addition reactions. The observed product mass distribution provides evidence also for abstraction reactions resulting in H2 formation, agreement with recent IR measurements. Complementary density functional theory calculations confirm stability species toward spontaneous and loss indicating that may be dominant route to involving neutral...

The gas-surface interaction of molecular hydrogen D2 with a thin film porous amorphous solid water (ASW) grown at 10 K by slow vapor deposition has been studied temperature-programmed-desorption (TPD) experiments. Molecular diffuses rapidly into the network ice. desorption occurring between and 30 is considered here as good probe effective surface ASW interacting gas. kinetics have systematically measured various coverages. A careful analysis based on Arrhenius plot method provided binding...

Icy dust grains in space act as catalytic surfaces onto which complex molecules form. These are synthesized through exothermic reactions from precursor radicals and, mostly, hydrogen atom additions. Among the resulting products species of biological relevance, such hydroxylamine—NH2OH—a molecule formation amino acids. In this Letter, laboratory experiments described that demonstrate NH2OH interstellar ice analogs for astronomically relevant temperatures via successive hydrogenation solid...

The amount of methanol in the gas phase and CO depletion from are still open problems astrophysics. In this work, we investigate solid-state hydrogenation CO-bearing species via H-exposure carbon monoxide, formaldehyde, methanol-thin films deposited on cold surfaces, paying attention to possibility a return phase. products probed infrared spectroscopy (reflection absorption spectroscopy), two types mass protocols: temperature-programmed desorption, during-exposure desorption techniques. case...

Context. Over 20 of the ~150 different species detected in interstellar and circumstellar media have also been identified icy environments. For most observed so far medium (ISM), abundant isomer a given generic chemical formula is stable one (minimum energy principle – MEP) with few exceptions such as, for example, CH3COOH/HCOOCH3 CH3CH2OH/CH3OCH3, whose formation thought to occur on mantles grains.

Dust grains in the interstellar medium are known to serve as first chemical laboratory where rich inventory of molecules synthesized. Here we present a study formation hydroxylamine--NH(2)OH--via non-energetic route NO + H (D) on crystalline H(2)O and amorphous silicate under conditions relevant dense clouds. Formation nitrous oxide (N(2)O) water (H(2)O, D(2)O) is also observed reaction network discussed. Hydroxylamine results detected temperature-programmed desorption (TPD) experiments,...

Any evolving system can change state via thermal mechanisms (hopping a barrier) or quantum tunneling. Most of the time, efficient classical dominate at high temperatures. This is why an increase temperature initiate chemistry. We present here experimental investigation O-atom diffusion and reactivity on water ice. explore 6-25 K range submonolayer surface coverages. derive law observe transition from to diffusion. Despite mass O, tunneling even 6 K. As consequence, solid-state astrochemistry...

The adsorption of polycyclic aromatic hydrocarbon (PAH) molecules on graphitic surfaces provides a model system with which to investigate weak van der Waals (vdW) interactions. There are few experimental investigations either the interaction between large PAH and graphite or binding layers. Determining energy in these molecular systems valuable benchmark for validating theoretical methods implementing interactions and, hence, also means interlayer graphite. Here, we coronene molecule highly...

Abstract Interstellar complex organic molecules are thought to be the building blocks of more prebiotic compounds. In particular, formamide (or methanimide, NH2CHO), is presented as a multifunctional precursor, starting point both pre-genetic and pre-metabolic species. NH2CHO widely observed in different astrophysical media well comets that may have had crucial role delivery exogenous material Earth. star-forming regions, gas phase synthesis possible, even if it still debated. this paper we...

Sticking of H and D atoms on interstellar dust grains is the first step in molecular hydrogen formation, which a key reaction InterStellar Medium (ISM). After studying sticking coefficients H2 D2 molecules amorphous silicate surfaces experimentally theoretically, we extrapolate results to coefficient propose formulae that gives both silicates icy grains. In our experiments, used King Wells method for measuring surface held at 10 K. It consists with QMS (quadrupole mass spectrometer) signals...

The formation of the first monolayer water molecules on bare dust grains is primary importance to understand growth icy mantles that cover in interstellar medium. In this work, we explore experimentally from O2 + D reaction silicate surfaces simulates present diffuse clouds at visual extinctions (AV < 3 mag). For comparison, also study covered with amorphous ice representing dense ⩾ Our studies focus sub-monolayer and regimes using reflection absorption infrared spectroscopy...

Context. The formation of carbon dioxide ice in quiescent regions molecular clouds has not yet been fully understood, even though CO2 is one the most abundant species interstellar ices.

Highly energetic translational energy distributions are reported for hydrogen and deuterium molecules desorbing associatively from the atomic chemisorption states on highly oriented pyrolytic graphite (HOPG). Laser assisted associative desorption is used to measure time of flight a (deuterium) saturated HOPG surface produced by exposure thermal atom source at around 2100K. The normal very broad, ∼0.5to∼3eV, with peak ∼1.3eV. highest measured close theoretically predicted barrier height....

At the low temperatures of interstellar dust grains, it is well established that surface chemistry proceeds via diffusive mechanisms H atoms weakly bound (physisorbed) to surface. Until recently, however, was unknown whether heavier than hydrogen could diffuse rapidly enough on grains react with other accreted species. In addition, models still require simple reduction as oxidation reactions occur explain abundances various molecules. this paper we investigate O-atom diffusion and reactivity...

Context . CO and N 2 are two abundant species in molecular clouds. molecules heavily depleted from the gas phase towards centre of pre-stellar cores, whereas maintains a high abundance. For example, cloud L183, is by factor ≈400 its with respect to outer regions cloud, only ≈20. The reason for this difference not yet clear, since have identical masses, similar sticking properties, relatively close energy adsorption. Aims We present study CO-N system sub-monolayer regimes, aim measure,...

Context. Beyond NH 3 , only one primary alkylamine, CH 2 has been identified in the interstellar medium and reason why is still not understood: its formation could occur gas phase or icy environments. Aims. To consider any possible difference between of secondary amines, we studied hydrogenation processes CN NC, which would lead to simple NHCH respectively. Methods. Experimentally, NC was carried out under ultra-high vacuum, using two beamlines inject nitrile/isonitrile H onto substrate...

Context. Formic acid (HCOOH) is the simplest organic carboxylic in chemical synthesis and significant species interstellar chemistry. HCOOH has been abundantly detected ices, dense molecular clouds star-forming regions. Aims. Laboratory hydrogenation experiments of molecules with H atoms were performed two cryogenic ultra-high vacuum devices on amorphous solid water highly oriented pyrolytic graphite surfaces. The aim this work to study reactivity at low surface temperature 10 K, coverage...

The possible role of neutral PAHs as catalysts for H2 formation in the interstellar medium is investigated by a combined experimental and density function theory study superhydrogenation coronene (C24H12). calculations suggest efficient hydrogenation both edge centre sites, along with competing abstraction reactions to form series catalytic cycles. Scanning tunneling microscopy thermal desorption measurements have been used provide direct evidence superhydrogenated result exposure D atoms....

The absorption cross section and the ionization quantum yield of H2O have been measured using a synchrotron radiation source between 9 22 eV. Comparison two curves highlights competition relaxation processes for Rydberg states converging to first à 2A 1 second 2B 2 excited H2O+. with D2O yields, derived from Katayama et al (1973 J. Chem. Phys. 59 4309), reveals specific energy-dependent deuteration effects on competitive predissociation autoionization channels. Direct was found be only...

Direct D atom desorption, as well associative desorption of D2 molecules are observed in thermal from atoms chemisorbed on a C(0001) surface by combining laser induced T-jumps with resonance enhanced multiphoton ionization detection. Bleaching curves suggest that different classes clusters present the initial surface. The energy resolved atomic flux, obtained via time flight techniques, compares favorably (via detailed balance) theoretical calculations sticking. Density functional theory...

Nitrogen monoxide (NO) is observed in the gas phase of molecular clouds. It may accrete on dust grains, and there its hydrogenation should lead to hydroxylamine (NH2OH), same way that CO transformed into methanol (CH3OH) surface grains. NO has been said barrier-less, whereas proceed through quantum tunneling, thus slower. However, CH3OH widely considered as a proxy complex organic molecules while remains undetected. We aim at studying, analyzing, understanding chemical network cold surfaces....