We set a equal to a negative number, in particular a = -2.0 a0, because we are only concerned with large values of 𝑟 IJ%%,) in the present application. (Note: 1 a0 ≡ 1 bohr ≈ 0.5292 Å.) We set f equal to 2.0 a0 -1 and b equal to 7.5 a0 because these choices of the parameters gave physical fits.