Based on which experiment did the Rutherford nuclear model come from?

Explanation

Ernst Rutherford was engaged in experiments on a-particles emitted by some radioactive elements and explanation of the results gave an explanation of the atomic model.
According to this the entire positive charge and most of the mass of the atom is concentrated in small volume called the nucleus with electron revolving around the nucleus just as planets revolve around the Sun which is also called planetary model of atom or Rutherford nuclear model which we have accepted today.
However, it could not explain why atoms emit light of only discrete wavelengths. For example, how could an atom as simple as hydrogen, consisting of a single electron and a single proton, emit a complex spectrum of specific wavelengths?