Hydrogen atom recombination on graphite at 10 K via the Eley–Rideal mechanism

Rutigliano, M.; Cacciatore, M.; Billing, Gert Due

doi:10.1016/s0009-2614(01)00366-9

Cited by 90 publications

(84 citation statements)

References 19 publications

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“…The rovibrational excitation of the molecule allows the determination of the mechanisms to form H 2 (Lemaire et al 2010;Islam et al 2007). Different mechanisms have been studied theoretically by several groups (Rutigliano et al 2001;Ree et al 2002;Morisset et al 2003;Morisset et al 2004a;Morisset et al 2005;Martinazzo & Tantardini 2006;Bachellerie et al 2007). In our KMC simulations it is not possible to extract the energy of the H 2 formed.…”

Section: Discussionmentioning

confidence: 99%

“…Density functional theory (DFT) calculations show that while the chemisorption of one H atom is associated with an important barrier, the formation of the para dimer is barrier-less and that the formation of the ortho dimer has a reduced barrier (Rougeau et al 2006). The formation of H 2 that involves chemisorbed atoms through the ER mechanism has been studied by DFT (Jeloaica & Sidis 1999;Ferro & Allouche 2003) and dynamics calculations (Rutigliano et al 2001;Ree et al 2002;Morisset et al 2003;2004b;Martinazzo & Tantardini 2006). Based on these calculations, different mechanisms have been proposed to contribute to the H 2 formation through the ER mechanisms: the direct ER that involves isolated H atoms (monomers, Morisset et al 2003;2004b;Martinazzo & Tantardini 2006), barrier-less formation of H 2 involving one H atom in a para-dimer configuration (Bachellerie et al 2007) and formation by diffusing H atoms in physisorbed states (Bonfanti et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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When sticking influences H₂formation

Cazaux¹,

Morisset

Spaans³

et al. 2011

A&A

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Aims. Because of their catalytic properties, interstellar dust grains are crucial to the formation of H 2 , the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick on dust grains. In this study we determine the sticking coefficient of H atoms chemisorbed on graphitic surfaces, and estimate its impact on the formation of H 2 . Methods. The sticking probability of H atoms chemisorbed onto graphitic surfaces is obtained using a mixed classical-quantum dynamics method. In this, the H atom is treated quantum-mechanically and the vibrational modes of the surface are treated classically. The implications of sticking for the formation of H 2 are addressed by using kinetic Monte Carlo simulations that follow how atoms stick, move and associate with each other on dust surfaces of different temperature.Results. In our model, molecular hydrogen forms very efficiently for dust temperatures lower than 15 K through the involvement of physisorbed H atoms. At dust temperatures higher than 15 K and gas temperatures lower than 2000 K, H 2 formation differs strongly if the H atoms coming from the gas phase have to cross a square barrier (usually considered in previous studies) or a barrier obtained by density functional theory (DFT) calculations to become chemisorbed. The product of the sticking times efficiency can be increased by many orders of magnitude when realistic barriers are considered. If graphite phonons are taken into account in the dynamics calculations, then H atoms stick better on the surface at high energies, but the overall H 2 formation efficiency is only slightly affected. Our results suggest that H 2 formation can proceed efficiently in photon-dominated regions, X-ray dominated regions, hot cores and in the early Universe when the first dust is available.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

When sticking influences H₂formation

Cazaux¹,

Morisset

Spaans³

et al. 2011

A&A

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“…[13] and in numerous other papers (see, for example, refs. [6,16]). We shall therefore only briefly summarize the most important points here.…”

Section: Collisional Methods and Pes Determinationmentioning

confidence: 99%

“…In a previous work, [6] we constructed an analytical PES for Reaction (1) as a sum of pairwise interactions using the ab initio data of ref. [14] for the H-graphite system.…”

Section: Introductionmentioning

confidence: 99%

Isotope and Surface Temperature Effects for Hydrogen Recombination on a Graphite Surface

Rutigliano

Cacciatore

2008

ChemPhysChem

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We highlight the isotope and surface temperature effects for hydrogen atom recombination on a graphite surface. The reaction dynamics is studied using the semiclassical collisional method, according to which the mass and temperature effects are due to the coupling between the H/D dynamics and the dynamics of the phonon excitation/de-excitation mechanism of the substrate. All possible collisional schemes with H/D adsorbed on the surface and H/D impinging from the gas phase are considered. In particular, we focus on the recombination reaction between an H atom colliding with a D atom adsorbed on the surface and a D atom incident on an H adatom. For H(2) and D(2) formation, the surface temperature effect is investigated by comparing the results obtained for T(S)=800 K with those obtained at T(S)=500 K and T(S)=100 K. Despite the low masses involved in the dynamics, effective isotope and temperature effects were observed on the recombination probabilities, reaction energetics, and roto-vibrational states of formed molecules. The results show the need for correct treatment of the multiphonon excitation mechanism in molecule-surface interactions.

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“…Moreover, a wide spectrum of vibrationally excited molecules can be formed in the recombinative desorption process of atomic hydrogen on some metal surfaces by Eley-Rideal and hot-atom reactions [40].…”

Section: B Neutral Direct Simulation Monte Carlo (Dsmc) Modulementioning

confidence: 99%