Charge Transfer Data Needs for Cometary X-ray Emission Modeling.

The emission of x-rays has been observed from nearly twenty comets and evidence exists that it is the result of radiative decays from highly-excited, highly-charged solar wind ions following charge exchange with neutral species, mostly water, in the cometary atmosphere. We review the progress to date in constructing models of the x-ray emission. However, the construction of accurate models is impeded by the near tack of reliable state-selective charge exchange cross section data for the relevant neutral species (H[sub 2]O, CO, CO[sub 2], etc.). The progress, and difficulties, of theoretical studies for the relevant collision processes is discussed with a particular focus on the breakdown of approximations made in the emission models. [ABSTRACT FROM AUTHOR]