FORMATION OF MOLECULAR HYDROGEN FROM METHANE ICE

Journal Article · Fri Oct 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/721/2/1656· OSTI ID:21464753

Jiao, He; Kun, Gao ^[1]; Vidali, Gianfranco; Bennett, Chris J; Kaiser, Ralf I ^[2]

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1. Physics Department, Syracuse University, Syracuse, NY 13244 (United States)
2. Chemistry Department, University of Hawaii at Minoa, Honolulu, HI 96822 (United States)

To study the formation of molecular hydrogen in the wake of the processing of interstellar ices by energetic cosmic-ray particles, we investigated the interaction of energetic electrons, as formed in the track of galactic cosmic-ray particles, with deuterated methane ices (CD{sub 4}) at 11 K. The energetic electrons mimic energy-transfer processes that occur in the track of the trajectories of energetic cosmic-ray particles; deuterated methane ice was utilized to discriminate the molecular deuterium (m/z = 4) formed during the radiation exposure from the residual molecular hydrogen gas (m/z = 2) released inside the ultrahigh vacuum scattering chamber from outgassing of the stainless steel material. The ices were characterized online and in situ using Fourier transform infrared spectroscopy, while the evolution of the molecular deuterium (D{sub 2}) into the gas phase was monitored using a mass spectrometer. A mass spectrometric signal proportional to the number density of the deuterium molecules generated inside the ice and released during the irradiation was analyzed kinetically using a set of coupled rate equations. From the fit to the experimental data, we obtain activation energies for the diffusion of atomic deuterium (E{sub 0} = 37 {+-} 1 meV), and for the desorption of atomic (E{sub 1} = 32 {+-} 1 meV) and molecular deuterium (E{sub 2} = 32 {+-} 1 meV). These energies are placed in context and then transferred to atomic and molecular hydrogen to yield astrophysically relevant data. The experimental yield of molecular deuterium is then used to calculate the formation rate of molecular hydrogen due to cosmic-ray interaction with ice-covered grains in dense clouds.

• OSTI ID: 21464753
• Journal Information: Astrophysical Journal, Vol. 721, Issue 2; Other Information: DOI: 10.1088/0004-637X/721/2/1656; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACTIVATION ENERGY
ASTRONOMY
ASTROPHYSICS
COSMIC RADIATION
DEUTERIUM
ENERGY TRANSFER
FOURIER TRANSFORM SPECTROMETERS
HYDROGEN
ICE
MASS SPECTROMETERS
MASS SPECTROSCOPY
METHANE
REACTION KINETICS
STAINLESS STEELS
TAIL ELECTRONS
ALKANES
ALLOYS
CARBON ADDITIONS
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
FERMIONS
HIGH ALLOY STEELS
HYDROCARBONS
HYDROGEN ISOTOPES
IONIZING RADIATIONS
IRON ALLOYS
IRON BASE ALLOYS
ISOTOPES
KINETICS
LEPTONS
LIGHT NUCLEI
MEASURING INSTRUMENTS
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHYSICS
RADIATIONS
SPECTROMETERS
SPECTROSCOPY
STABLE ISOTOPES
STEELS
TRANSITION ELEMENT ALLOYS