Who provided evidence for the existence of an atomic nucleas?

In 1911, the scientist Ernest Rutherford directed a beam of alpha particles (each one equivalent to a helium nucleus, with 2 protons and 2 neutrons) at a thin sheet of gold foil - many of the alpha particles (with a charge of +2) were deflected straight back, repelled by the positively charged atomic nuclei within the gold foil. This provided experimental evidence for the existence of the nucleus for the first time.