How does ionization of gas molecule affect the translational kinetic energy of the molecule?

Some things I understand to be true: When we raise the temperature of a gas to around 10-20,000 Kelvin, the molecules of gas start to ionize, form a plasma, according to the Saha equation. The temperature of a gas relates to the average kinetic energy, which for monotomic molecules, e.g. argon atoms, comprises the translational kinetic energy of the atoms of the gas (cf diatomic molecules, such as nitrogen, which can also hold rotational, and vibrational KE) So... thinking this through... let's imagine a single atom of argon traveling along, at constant velocity $v$ , and having kinetic energy $0.5mv^2$ . Then, we suppose that its KE is high enough that it can ionize, and convert a large part of the KE into electrostatic PE. So ... the resulting ion and electron basically just stop moving? That would seem to violate laws of relativity, and mean we can extract energy from relative velocity? e.g. would allow us to convert the motion of the earth into usable energy? Since such things are generally not possible, I'm going to assume there are some flaws in my understanding of what happens during ionization of a monotomic gas atom/molecule?