const h     = 6.626_070_040e-34*J*s
const h_bar = h / (2pi)
const electron_rest_mass = 9.10938356e-31 * kg
const c     = 299_792_458.0 * m / s
const electron_rest_energy = c^2 * electron_rest_mass
const r_c   = h_bar / (c*electron_rest_mass) # reduced compton wavelength of electron
const alpha = 1/137.04 # fine structure constant
