scholarly journals Photon-induced desorption of larger species in UV-irradiated methane ice

2020 ◽  
Vol 493 (1) ◽  
pp. 821-829
Author(s):  
H Carrascosa ◽  
G A Cruz-Díaz ◽  
G M Muñoz Caro ◽  
E Dartois ◽  
Y-J Chen
Keyword(s):  
Gas Phase ◽  
Uv Irradiation ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Quadrupole Mass ◽  
Gas Phases ◽  
Uv Lamp ◽  
Uv Photons ◽  
Molecular Abundances

ABSTRACT At the low temperatures found in the interior of dense clouds and circumstellar regions, along with H2O and smaller amounts of species such as CO, CO2 or CH3OH, the infrared features of CH4 have been observed on icy dust grains. Ultraviolet (UV) photons induce different processes in ice mantles, affecting the molecular abundances detected in the gas phase. This work aims to understand the processes that occur in a pure CH4 ice mantle subjected to UV irradiation. We studied photon-induced processes for the different photoproducts arising in the ice upon UV irradiation. Experiments were carried out in ISAC, an ultra-high vacuum chamber equipped with a cryostat and an F-type UV lamp reproducing the secondary UV field induced by cosmic rays in dense clouds. Infrared spectroscopy and quadrupole mass spectrometry were used to monitor the solid and gas phases, respectively, during the formation, irradiation and warming-up of the ice. Direct photodesorption of pure CH4 was not observed. UV photons form CHx· and H· radicals, leading to photoproducts such as H2, C2H2, C2H6 and C3H8. Evidence for the photodesorption of C2H2 and photochemidesorption of C2H6 and C3H8 was found; the latter species is so far the largest molecule found to photochemidesorb. 13CH4 experiments were also carried out to confirm the reliability of these results.

Photon and thermal processing of CH3NH2-bearing ices. Synthesis of prebiotic species at low temperature (such as formamide, ethylamine, and methylcyanide), and N-heterocycles during warm up.

2021 ◽  
Author(s):  
Héctor Carrascosa ◽  
Cristóbal González Díaz ◽  
Guillermo M. Muñoz Caro ◽  
Pedro C. Gómez ◽  
María Luz Sanz
Keyword(s):  
Vacuum Chamber ◽  
Organic Molecules ◽  
Solid Phase ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Quadrupole Mass ◽  
Warm Up ◽  
Methyl Cyanide ◽  
Interstellar Ice ◽  
Complex Organic

<p>Hexamethylentetramine has drawn a lot of attention due to its potential to produce prebiotic species. This work aims to gain a better understanding in the chemical processes concerning methylamine under astrophysically relevant conditions. In particular, this work deeps into the formation of N-heterocycles in interstellar ice analogs exposed to UV radiation, which may lead to the formation of prebiotic species.</p> <p>Experimental simulations of interstellar ice analogs were carried out in ISAC. ISAC is an ultra-high vacuum chamber equipped with a cryostat, where gas and vapour species are frozen forming ice samples. Infrared and ultraviolet spectroscopy were used to monitor the solid phase, and quadrupole mass spectrometry served to measure the composition of the gas phase. The variety of species detected after UV irradiation of ices containing  methylamine revealed the presence of 12 species which have been already detected in the ISM, being 4 of them typically classified as complex organic molecules: formamide (HCONH<sub>2</sub>), methyl cyanide (CH<sub>3</sub>CN), CH<sub>3</sub>NH and CH<sub>3</sub>CHNH. Warming up of the irradiated CH<sub>3</sub>NH<sub>2</sub>-bearing ice samples lead to the formation of trimethylentriamine (TMT), a N-heterocycle precursor of HMT, and the subsequent synthesis of HMT at temperatures above 230 K.</p>

Low Temperature Laser-Assisted Gas Phase Reactivity of TMGa with NH3 and Oxygen-Containing Compounds (H2O, CH3OH, O(CH3)2) in Constrained Pulsed Expansions

2002 ◽  
Vol 743 ◽  
Author(s):  
Alexander Demchuk ◽  
Michael Lynch ◽  
Steven Simpson ◽  
Brent Koplitz
Keyword(s):  
Gas Phase ◽  
Vacuum Chamber ◽  
Cluster Formation ◽  
High Vacuum ◽  
Oxygen Species ◽  
Quadrupole Mass ◽  
High Vacuum Chamber ◽  
Arf Excimer Laser ◽  
Gas Nozzle ◽  
193 Nm

ABSTRACTThe present work reports on the study of III-V gas phase reactivity in constrained gas pulse expansions of trimethylgallium (TMGa) and oxygen derivative compounds (H2O, CH3OH, O(CH3)2) with and without ammonia. The precursors are introduced separately into a high vacuum chamber via a multipulsed gas nozzle assembly. The gas mixtures are then exposed to a UV pulse from an ArF excimer laser (λ=193 nm) and the products are mass analyzed with a quadrupole mass spectrometer. The efficient laser-assisted growth of Ga-O-containing clusters in the form of [(CH3)2GaOR] x, where R is H or CH3, has been revealed. Different behavior can be seen in the reaction of TMG and the oxygen species depending on the presence of H atoms bonded to the oxygen. Significant influence of NH3 on cluster formation and oxygen incorporation is demonstrated.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

Study Of Al Surface Segregation In Icosahedral A162Cu25.5Fe12.5

1998 ◽  
Vol 553 ◽  
Author(s):  
M. GIL-GAVATZ ◽  
D. Rouxel ◽  
P. Pigeat ◽  
B. Weber ◽  
J.-M. Dubois
Keyword(s):  
Surface Segregation ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Spectrometer ◽  
Temperature Dependent ◽  
Self Diffusion ◽  
Different Temperatures ◽  
High Vacuum Chamber

AbstractSurface segregation of aluminium was observed during oxidation experiments of icosahedral A162Cu25.5 Fel12.5, performed in-situ and at different temperatures in the ultra-high vacuum chamber of a scanning Auger electron spectrometer. Two regimes, below and above 770K, were observed in relation with severe segregation of Al atoms at the surface for T > 770K. We postulate that this temperature dependent segregation rate is representative of the aluminium transport towards the surface of the quasicrystal. By analogy with classical diffusion experiments, we can thus determine reasonable estimates of the activation energy for Al self-diffusion in this quasicrystal. The results are consistent with the existence of phason flips below 770K and thermal vacancies above this temperature.

Toward Growing III-V Clusters with Metalorganic Precursors

1997 ◽  
Vol 468 ◽  
Author(s):  
A. Demchuk ◽  
J. Porter ◽  
B. Koplitz
Keyword(s):  
Excimer Laser ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Quadrupole Mass ◽  
Reaction Region ◽  
High Vacuum Chamber ◽  
Arf Excimer Laser ◽  
193 Nm ◽  
Pulsed Nozzle

ABSTRACTThe present work reports on the formation of GaN-containing clusters from metalorganic precursors by combining pulsed laser photolysis and pulsed nozzle methods. Ammonia (NH3) and triethylgallium (C2H5)3Ga (TEG) or trimethylgallium (CH3)3Ga (TMG) with He, Ar, or N2 as the carrier gas are introduced into a high vacuum chamber via a specialized dual pulsed nozzle source. The light from an ArF excimer laser (193 nm, 23 ns FWHM) is focused into the mixing and reaction region of the nozzle source, and the products are then mass analyzed with a quadrupole mass spectrometer. Efficient laser-assisted growth of (GaN)x-containing clusters is shown with this technique.

Ultra-high-vacuum chamber

Vacuum ◽  
1965 ◽  
Vol 15 (7) ◽  
pp. 372-373
Author(s):  
CONSOLIDATEDVACUUMCORPORATION
Keyword(s):  
Vacuum Chamber ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Vacuum Chamber ◽  
Ultra High Vacuum Chamber

CORRELATION AMONG THE ELECTRONIC STATE IN Sn-DOPED YBCO SYSTEM

1991 ◽  
Vol 05 (08) ◽  
pp. 581-585
Author(s):  
H. ZHANG ◽  
S.Q. FENG ◽  
Q.R. FENG ◽  
X. ZHU
Keyword(s):  
Content Analysis ◽  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Strong Correlation ◽  
Single Phase ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Electronic States ◽  
Ultra High Vacuum ◽  
X Ray

We have performed an X-ray photoelectron spectroscopy investigation on single-phase samples of Sn -doped YBCO system, together with structure analysis, oxygen content analysis, and superconductivity measurements. The experiment gave evidence that there is a strong correlation between the electronic states of copper and oxygen. When the sample was heated to 600°C for 20 minutes in vacuum chamber, the oxygen escaped from the sample, the binding energy of Cu 2p was decreased, and the two indistinct components of O 1s became clear. Keeping the sample in ultra-high vacuum for 24 hours, a similar result was obtained.

scholarly journals Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

2021 ◽  
Vol 75 (6) ◽  
Author(s):  
Duncan V. Mifsud ◽  
Zoltán Juhász ◽  
Péter Herczku ◽  
Sándor T. S. Kovács ◽  
Sergio Ioppolo ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Thermal Processing ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Quadrupole Mass ◽  
Thermal Chemistry ◽  
Physico Chemical ◽  
Solar System Bodies ◽  
Molecular Excitation

Abstract The modelling of molecular excitation and dissociation processes relevant to astrochemistry requires the validation of theories by comparison with data generated from laboratory experimentation. The newly commissioned Ice Chamber for Astrophysics-Astrochemistry (ICA) allows for the study of astrophysical ice analogues and their evolution when subjected to energetic processing, thus simulating the processes and alterations interstellar icy grain mantles and icy outer Solar System bodies undergo. ICA is an ultra-high vacuum compatible chamber containing a series of IR-transparent substrates upon which the ice analogues may be deposited at temperatures of down to 20 K. Processing of the ices may be performed in one of three ways: (i) ion impacts with projectiles delivered by a 2 MV Tandetron-type accelerator, (ii) electron irradiation from a gun fitted directly to the chamber, and (iii) thermal processing across a temperature range of 20–300 K. The physico-chemical evolution of the ices is studied in situ using FTIR absorbance spectroscopy and quadrupole mass spectrometry. In this paper, we present an overview of the ICA facility with a focus on characterising the electron beams used for electron impact studies, as well as reporting the preliminary results obtained during electron irradiation and thermal processing of selected ices. Graphic Abstract

scholarly journals UV-Induced Formation of Ice XI Observed Using an Ultra-High Vacuum Cryogenic Transmission Electron Microscope and its Implications for Planetary Science

2021 ◽  
Vol 9 ◽  
Author(s):  
Akira Kouchi ◽  
Yuki Kimura ◽  
Kensei Kitajima ◽  
Hiroyasu Katsuno ◽  
Hiroshi Hidaka ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Solar System ◽  
Uv Irradiation ◽  
Transmission Electron Microscope ◽  
High Vacuum ◽  
Planetary Science ◽  
Ultra High Vacuum ◽  
Outer Solar System ◽  
Transmission Electron ◽  
Uv Dose

The occurrence of hydrogen atom-ordered form of ice Ih, ice XI, in the outer Solar System has been discussed based on laboratory experiments because its ferroelectricity influences the physical processes in the outer Solar System. However, the formation of ice XI in that region is still unknown due to a lack of formation conditions at temperatures higher than 72 K and the effect of UV-rays on the phase transition from ice I to ice XI. As a result, we observed the UV-irradiation process on ice Ih and ice Ic using a newly developed ultra-high vacuum cryogenic transmission electron microscope. We found that ice Ih transformed to ice XI at temperatures between 75 and 140 K with a relatively small UV dose. Although ice Ic partially transformed to ice XI at 83 K, the rate of transformation was slower than for ice Ih. These findings point to the formation of ice XI at temperatures greater than 72 K via UV irradiation of ice I crystals in the Solar System; icy grains and the surfaces of icy satellites in the Jovian and Saturnian regions.

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