Open AccessSuprathermal chemical reactions driven by fast hydrogen atoms in cometary comae
Author(s) -
Rodgers S. D.,
Charnley S. B.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08606.x
Subject(s) - physics , photodissociation , endothermic process , hydrogen , atomic physics , coma (optics) , chemical reaction , molecule , astrophysics , chemical physics , photochemistry , chemistry , biochemistry , adsorption , quantum mechanics
We have investigated the role that energetic hydrogen atoms, produced in cometary comae by the photodissociation of water molecules, could have in driving chemical reactions that are endothermic, or possess activation energy barriers. We have developed a model of the density and energy spectrum of these atoms in the coma and have incorporated a number of reactions driven by fast H atoms into our existing coma model. We find that, in high‐activity comets close to the Sun, such reactions are competitive with direct photodissociation as the principal destruction mechanism for molecules with long lifetimes in the solar radiation field. We show that measurements of the CH 2 OH : CH 3 O ratio may be used to assess the importance of suprathermal reactions in the coma. We also confirm that these reactions are probably unable to account for the observed HNC : HCN ratios.