Question

Can atoms capture beta particles or secondary electrons into their orbits and become anions?

Answer 1

Beta particle energies are of order 105105 eV, which is vastly greater than typical electron affinities of order 11 eV. The beta electron is not going to end up bound to another atom until it's had a chance to dissipate the unwanted 99,99999,999 eV. The energy is typically dissipated by colliding with other atoms and ionising them.