Presentation #411.09 in the session Cometary Volatiles (iPosters).
Forbidden atomic oxygen lines in emission are ubiquitous for cometary spectra in the visible region, at 557.7 nm and 630.0/636.4 nm. Coma of a comet at ~1 au from the Sun is dominated by water as parent molecule, and photodissociation reactions of water produce oxygen atoms in meta-stable states such as O(1D) and O(1S), from which the forbidden emission lines are emitted. High resolution spectra of comets reported in literatures showed that the line widths of green line were wider than those of red lines although the opposite was predicted theoretically by Festou (1981). Kawakita (2022) recently recalculated photodissociation rates, excess energies, and total kinetic energies released for the photolysis of H2O producing O(1S) by solar UV radiation field, and found that the total kinetic energies released for atomic oxygen are larger for the green line than the red lines. This finding may be the reason why the green line was usually reported wider than the red lines in comets. Here we present the results of Monte-Carlo simulation for line profiles of the forbidden atomic oxygen lines in comets at ~1 au from the Sun based on Kawakita (2022). We also compare our results with the line widths observed in comets so far.