Atom-electron interaction in an x ray tube

Question

My question has to do with the absorption of an electron by an atom.

When an electron approaches the atom there are two possibilities. Either the electron will do a "slingshot" around the nucleus (this is called Bremsstrahlung and a certain radiation is emitted when it occurs) or a characteristic interaction will occur (in which the atom is ionized and the "missing" electron is replaced by one from a higher energy shell, emitting characteristic radiation). The characteristic interaction is known to happen with the electrons of the first shell (K) which for tungsten need an energy of 69.5 keV to be emitted.

My question is, is it possible for that kind of reaction to happen on a higher shell, for example the L shell for which the elections need keV of energy to be ejected? If yes then what happens when an electron is "shot" at an atom with an energy of 70keV? Does it cause Bremsstrahlung or does it force an electron to be ejected? If the second happens then which of the two electrons will be more likely to be ejected? One in the K shell or one in the L shell?

The video below explains the Characteristic interaction between an atoms and an electron:

https://youtu.be/FjeF1xQHdwk

Answer 1

Electron-impact ionization is larger for the L-shell than for the K-shell. See for example the values of the dipole constant $M^2$ in the paper by Kim et al in Phys Rev A (2000).

Other things can also happen. The incident electron can make a transition to an unoccupied bound level, which would give a photon of 70 keV. The process (measured in inverse photoelectron spectroscopy) has a very small cross section.