scholarly journals Using Surface Science Techniques to Investigate the Interaction of Acetonitrile with Dust Grain Analogue Surfaces

2021 ◽  
Author(s):  
Emily R. Ingman ◽  
Amber Shepherd ◽  
Wendy A. Brown
Keyword(s):  
Surface Science ◽  
Thermal Processing ◽  
Desorption Energy ◽  
Water Ice ◽  
Ice Surface ◽  
Coverage Analysis ◽  
Wide Range ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Temperature Programmed ◽  
Dust Grain

Surface science methodologies, such as reflection-absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD), are ideally suited to studying the interaction of molecules with model astrophysical surfaces. Here we describe the use of RAIRS and TPD to investigate the adsorption, interactions and thermal processing of acetonitrile and water containing model ices grown under astrophysical conditions on a graphitic dust grain analogue surface. Experiments show that acetonitrile physisorbs on the graphitic surface at all exposures. At the lowest coverages, repulsions between the molecules lead to a decreasing desorption energy with increasing coverage. Analysis of TPD data gives monolayer desorption energies ranging from 28.8 - 39.2 kJ mol-1 and an average multilayer desorption energy of 43.8 kJ mol-1. When acetonitrile is adsorbed in the presence of water ice, the desorption energy of monolayer acetonitrile shows evidence of desorption with a wide range of energies. An estimate of the desorption energy of acetonitrile from CI shows that it is increased to ~37 kJ mol-1 at the lowest exposures of acetonitrile. Amorphous water ice also traps acetonitrile on the graphite surface past its natural desorption temperature, leading to volcano and co-desorption. RAIRS data show that the C≡N vibration shifts, indicative of an interaction between the acetonitrile and the water ice surface.

scholarly journals Surface science investigations of the role of CO 2 in astrophysical ices

2013 ◽  
Vol 371 (1994) ◽  
pp. 20110578 ◽  
Author(s):  
John L. Edridge ◽  
Kati Freimann ◽  
Daren J. Burke ◽  
Wendy A. Brown
Keyword(s):  
Surface Science ◽  
Amorphous Solid ◽  
Temperature Programmed Desorption ◽  
Surface Data ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Temperature Programmed ◽  
Astrophysical Ices ◽  
Dust Grain ◽  
Science Investigations

We have recorded reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) data for a range of CO 2 -bearing model astrophysical ices adsorbed on a graphitic dust grain analogue surface. Data have been recorded for pure CO 2 , for CO 2 adsorbed on top of amorphous solid water, for mixed CO 2 :H 2 O ices and for CO 2 adsorbed on top of a mixed CH 3 OH:H 2 O ice. For the TPD data, kinetic parameters for desorption have been determined, and the trapping behaviour of the CO 2 in the H 2 O (CH 3 OH) ice has been determined. Data of these types are important as they can be used to model desorption in a range of astrophysical environments. RAIR spectra have also shown the interaction of the CO 2 with H 2 O and CH 3 OH and can be used to compare with astronomical observations, allowing the accurate assignment of spectra.

scholarly journals Implications of Ice Morphology for Comet Formation

2005 ◽  
Vol 13 ◽  
pp. 491-494 ◽  
Author(s):  
M. P. Collings ◽  
J. W. Dever ◽  
M. R. S. McCoustra ◽  
H. J. Fraser
Keyword(s):  
Surface Science ◽  
High Vacuum ◽  
Binding Energies ◽  
Ultra High Vacuum ◽  
Water Ice ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Thermodynamic Conditions ◽  
Temperature Programmed ◽  
Additional Constraints ◽  
Ice Morphology

AbstractLaboratory surface science under ultra-high vacuum (UHV) conditions allows us to simulate the growth of ices in astrophysical environments. Using the techniques of temperature programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS) and micro-balance methods, we have studied binary ice systems consisting of water (H2O) and variety of other species including carbon monoxide (CO), at astrophysically relevant conditions of temperature and pressure. We present results that demonstrate that the morphology of water ice has an important influence on the behavior of such systems, by allowing processes such as diffusion and trapping that can not be understood through a knowledge of the binding energies of the species alone. Through an understanding of the implications of water ice morphology on the behavior of ice mixtures in the interstellar environment, additional constraints can be placed on the thermodynamic conditions and ice compositions during comet formation.

scholarly journals Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

2019 ◽  
Vol 15 (S350) ◽  
pp. 370-371
Author(s):  
Henda Chaabouni ◽  
Stephan Diana ◽  
Thanh Nguyen
Keyword(s):  
Energy Distribution ◽  
Thermal Desorption ◽  
Interstellar Dust ◽  
Binding Energies ◽  
Desorption Energy ◽  
Exponential Factor ◽  
Water Ice ◽  
Ice Surface ◽  
Crystalline Water ◽  
Best Fit

AbstractThermal desorption experiments of Formamide (NH2CHO) and methylamine (CH3NH2) were performed in LERMA-Cergy laboratory to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces, and to understand their interaction with water ice. We found that more than 95 % of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate, and is released into the gas phase with a desorption energy distribution Edes = (7460 – 9380) K, measured with the best-fit pre-exponential factor A=1018 s-1. Whereas, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes =3850-8420 K) is measured with the best-fit pre-exponential factor A=1012s-1. A fraction of solid methylamine, of about 0.15 monolayer diffuses through the water ice surface towards the HOPG substrate, and desorbs later, with higher binding energies (5050-8420 K), which exceed that of the crystalline water ice (Edes =4930 K), calculated with the same pre-exponential factor A=1012 s-1.

scholarly journals Variation of the sticking of methanol on low-temperature surfaces as a possible obstacle to freeze out in dark clouds

2020 ◽  
Vol 494 (3) ◽  
pp. 4119-4129
Author(s):  
K A K Gadallah ◽  
A Sow ◽  
E Congiu ◽  
S Baouche ◽  
F Dulieu
Keyword(s):  
Low Temperature ◽  
Surface Temperature ◽  
Gas Phase ◽  
Amorphous Solid ◽  
Vacuum System ◽  
Initial Value ◽  
Water Ice ◽  
Dark Clouds ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Temperature Programmed

ABSTRACT Sticking of gas-phase methanol on different cold surfaces – gold, 13CO, and amorphous solid water (ASW) ice – was studied as a function of surface temperature (7–40 K). In an ultrahigh-vacuum system, reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption methods were simultaneously used to measure methanol sticking efficiency. Methanol band strengths obtained by RAIRS vary greatly depending on the type of the surface. Nevertheless, both methods indicate that the sticking of methanol on different surfaces varies with surface temperature. The sticking efficiency decreases by 30${{\ \rm per\ cent}}$ as the surface temperature goes from 7 to 16 K, then gradually increases until the temperature is 40 K, reaching approximately the initial value found at 7 K. The sticking of methanol differs slightly from one surface to another. At low temperature, it has the lowest values on gold, intermediate values on water ice, and the highest values are found on CO ice, although these differences are smaller than those observed with temperature variation. There exists probably a turning point during the structural organization of methanol ice at 16 K, which makes the capture of methanol from the gas phase less efficient. We wonder if this observation could explain the surprising high abundance of gaseous methanol observed in dense interstellar cores, where it should accrete on grains. In this regard, a 30${{\ \rm per\ cent}}$ reduction of the sticking is not sufficient in itself but transposed to astrophysical conditions dominated by cold gas (∼15 K), which could reduce the sticking efficiency by two orders of magnitude.

scholarly journals Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

2018 ◽  
Vol 612 ◽  
pp. A47 ◽  
Author(s):  
H. Chaabouni ◽  
S. Diana ◽  
T. Nguyen ◽  
F. Dulieu
Keyword(s):  
Energy Distribution ◽  
Gas Phase ◽  
Thermal Desorption ◽  
Binding Energies ◽  
Desorption Energy ◽  
Exponential Factor ◽  
Water Ice ◽  
Ice Surface ◽  
Ice Surfaces ◽  
Best Fit

Context. Formamide (NH2CHO) and methylamine (CH3NH2) are known to be the most abundant amine-containing molecules in many astrophysical environments. The presence of these molecules in the gas phase may result from thermal desorption of interstellar ices. Aims. The aim of this work is to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces and to understand their interaction with water ice. Methods. Temperature programmed desorption (TPD) experiments of formamide and methylamine ices were performed in the sub-monolayer and monolayer regimes on graphite (HOPG) and non-porous amorphous solid water (np-ASW) ice surfaces at temperatures 40–240 K. The desorption energy distributions of these two molecules were calculated from TPD measurements using a set of independent Polanyi–Wigner equations. Results. The maximum of the desorption of formamide from both graphite and ASW ice surfaces occurs at 176 K after the desorption of H2O molecules, whereas the desorption profile of methylamine depends strongly on the substrate. Solid methylamine starts to desorb below 100 K from the graphite surface. Its desorption from the water ice surface occurs after 120 K and stops during the water ice sublimation around 150 K. It continues to desorb from the graphite surface at temperatures higher than160 K. Conclusions. More than 95% of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate and is released into the gas phase with a desorption energy distribution Edes = 7460–9380 K, which is measured with the best-fit pre-exponential factor A = 1018 s−1. However, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes = 3850–8420 K) is measured with the best-fit pre-exponential factor A = 1012 s−1. A fraction of solid methylamine monolayer of roughly 0.15 diffuses through the water ice surface towards the HOPG substrate. This small amount of methylamine desorbs later with higher binding energies (5050–8420 K) that exceed that of the crystalline water ice (Edes = 4930 K), which is calculated with the same pre-exponential factor A = 1012 s−1. The best wetting ability of methylamine compared to H2O molecules makes CH3NH2 molecules a refractory species for low coverage. Other binding energies of astrophysical relevant molecules are gathered and compared, but we could not link the chemical functional groups (amino, methyl, hydroxyl, and carbonyl) with the binding energy properties. Implications of these high binding energies are discussed.

scholarly journals The Growth of Semiconductor Thin Films Studied by RHEED

1990 ◽  
Vol 43 (5) ◽  
pp. 583
Author(s):  
GL Price
Keyword(s):  
Thin Films ◽  
Surface Science ◽  
High Vacuum ◽  
High Energy ◽  
Ultra High Vacuum ◽  
Large Area ◽  
Growth Modes ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Recent Developments

Recent developments in the growth of semiconductor thin films are reviewed. The emphasis is on growth by molecular beam epitaxy (MBE). Results obtained by reflection high energy electron diffraction (RHEED) are employed to describe the different kinds of growth processes and the types of materials which can be constructed. MBE is routinely capable of heterostructure growth to atomic precision with a wide range of materials including III-V, IV, II-VI semiconductors, metals, ceramics such as high Tc materials and organics. As the growth proceeds in ultra high vacuum, MBE can take advantage of surface science techniques such as Auger, RHEED and SIMS. RHEED is the essential in-situ probe since the final crystal quality is strongly dependent on the surface reconstruction during growth. RHEED can also be used to calibrate the growth rate, monitor growth kinetics, and distinguish between various growth modes. A major new area is lattice mismatched growth where attempts are being made to construct heterostructures between materials of different lattice constants such as GaAs on Si. Also described are the new techniques of migration enhanced epitaxy and tilted superlattice growth. Finally some comments are given On the means of preparing large area, thin samples for analysis by other techniques from MBE grown films using capping, etching and liftoff.

scholarly journals The role of radiolysis in the modelling of C2H4O2 isomers and dimethyl ether in cold dark clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 3414-3424
Author(s):  
Alec Paulive ◽  
Christopher N Shingledecker ◽  
Eric Herbst
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Thermal Method ◽  
Dark Clouds ◽  
Ice Surface ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modelled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C2H4O2 isomers – methyl formate (HCOOCH3), glycolaldehyde (HCOCH2OH), and acetic acid (CH3COOH) – and a chemically similar molecule, dimethyl ether (CH3OCH3), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

Influence of submonolayer sodium adsorption on the photoemission of the Cu(111)/water ice surface

2006 ◽  
Vol 125 (22) ◽  
pp. 224702 ◽  
Author(s):  
Tomas Vondrak ◽  
John M. C. Plane ◽  
Stephen R. Meech
Keyword(s):  
Water Ice ◽  
Ice Surface

Structural and Phase Transitions on Water Ice Surface Under HCl Exposure: Implication for Stratosphere Conditions

1998 ◽  
Vol 05 (01) ◽  
pp. 437-441
Author(s):  
N. M. Persiantseva ◽  
O. B. Popovicheva ◽  
T. V. Rakhimova
Keyword(s):  
Phase Transitions ◽  
Pressure Range ◽  
Phase State ◽  
Amorphous Solid ◽  
Surface Concentration ◽  
Uptake Kinetics ◽  
Water Ice ◽  
Uptake Efficiency ◽  
Ice Surface ◽  
Characteristic Values

The HCl-ice interaction has been investigated over a wide HCl pressure range of 10-7–10-4 Torr and ice temperatures 150–240 K. The Three characteristic values for HCl uptake efficiency were obtained which indicate the change of phase state and structure of the ice surface at increasing HCl pressure. The low value γ ≈ 0.1 ± 0.02 corresponds to HCl vapor interaction with pure ice and is realized at the atmosphere conditions. The value γ ≈ 0.5 ± 0.1 indicates the formation of hexahydrate HCl • 6H 2 O with increase of HCl pressure. And the largest value of γ ≈ 0.8 ± 0.1 is observed at appearance of liquid or amorphous solid 4:1 H 2O:HCl. The HCl uptake kinetics is analyzed. The flow of HCl molecules from the ice surface into the bulk is shown to play an important role in the redistribution of HCl molecules. It defines a low surface concentration of the adsorbed HCl molecules under stratospher condition at early times of interaction.

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