Molecular hydrogen formation on grain surfaces

Abstract

We reconsider H2 formation on grain surfaces. We develop a rate equation model which takes into account the presence of both physisorbed and chemisorbed sites on the surface, including quantum mechanical tunnelling and thermal diffusion. In this study, we took into consideration the uncertainties on the characteristics of graphitic surfaces. We calculate the H2 formation efficiency with the Langmuir Hinshelwood and Eley Rideal mechanisms, and discuss the importance of these mechanisms for a wide range of grain and gas temperatures. We also develop a Monte Carlo simulation to calculate the H2 formation efficiency and compare the results to our rate equation models. Our results are the following: (1) Depending on the barrier against chemisorption, we predict the efficiency of H2 formation for a wide range of grain and gas temperatures. (2) The Eley-Rideal mechanism has an impact on the H2 formation efficiency at high grain and gas temperatures. (3) The fact that we consider chemisorption in our model makes the rate equation and Monte Carlo approaches equivalent.

in "Light, dust and chemical evolution", Journal of Physics: Conference Series

References in corpus (2)

• Molecular hydrogen formation in the interstellar medium
• Some empirical estimates of the H2 formation rate in photon-dominated regions

Cited by in corpus (14)

• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• Chemical evolution of turbulent protoplanetary disks and the Solar nebula
• Mapping the cold dust temperatures and masses of nearby Kingfish galaxies with Herschel
• Formation of Water in the Warm Atmospheres of Protoplanetary Disks
• Formation of Organic Molecules and Water in Warm Disk Atmospheres
• Parameterizing the interstellar dust temperature
• A new look at sulphur chemistry in hot cores and corinos
• HE 0515-4414 - an unusual sub-damped Ly alpha system revisited
• The Thermodynamics of Molecular Cloud Fragmentation: Star Formation Under Non-Milky Way Conditions
• Catching the Birth of a Dark Molecular Cloud for the First Time
• Chemistry During the Gas-rich Stage of Planet Formation
• Chemical evolution of a protoplanetary disk
• A stochastic model and Monte Carlo algorithm for fluctuation-induced H${}_2$ formation on the surface of interstellar dust grains