Chemistry on Rotating Grain Surface: Ro-Thermal Desorption of Molecules from Ice Mantles

Abstract

It is widely believed that water and complex organic molecules (COMs) first form in the ice mantle of dust grains and are subsequently returned into the gas due to grain heating by intense radiation of protostars. Previous research on the desorption of molecules from the ice mantle assumed that grains are at rest which is contrary to the fact that grains are suprathermally rotating as a result of their interaction with an anisotropic radiation or gas flow. {To clearly understand how molecules are released in to the gas phase, the effect of grain suprathermal rotation on surface chemistry must be quantified}. In this paper, we study the effect of suprathermal rotation of dust grains spun-up by radiative torques on the desorption of molecules from icy grain mantles around protostars. We show that centrifugal potential energy due to grain rotation reduces the potential barrier of molecules and significantly enhances their desorption rate. We term this mechanism {\it rotational-thermal} or {\it ro-thermal} desorption. We apply the ro-thermal mechanism for studying the desorption of molecules from icy grains which are simultaneously heated to high temperatures and spun-up to suprathermal rotation by an intense radiation of protostars. We find that ro-thermal desorption is much more efficient than thermal desorption for molecules with high binding energy such as water and COMs. Our results have important implications for understanding the origin of COMs detected in star-forming regions and call for attention to the effect of suprathermal rotation of icy grains to use molecules as a tracer of physical conditions of star-forming regions.

9 figures, 16 pages; resubmitted to ApJ after the positive referee report

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Cited by in corpus (10)

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• Magnetic Properties of Dust Grains, Effect of Precession and Radiative Torque Alignment
• Alignment and rotational disruption of dust
• Rotational Desorption of Ice Mantles and Complex Molecules from Suprathermally Rotating Dust Grains around Young Stellar Objects
• CH3-Terminated Carbon Chains in the GOTHAM Survey of TMC-1: Evidence of Interstellar CH3C7N
• Observational evidence for rotational desorption of Complex Molecules by radiative torques from Orion BN/KL
• Dust rotational dynamics in non-stationary shock: rotational disruption of nanoparticles by stochastic mechanical torques and spinning dust emission
• Evolution of Dust and Water Ice in Cometary Comae by Radiative Torques
• On planet formation around supermassive black holes and the grain disruption barriers by radiative torques
• Rotational Disruption of Dust and Ice by Radiative Torques in Protoplanetary Disks and Implications for Observations