How did Ernest Rutherford later prove that alpha particles are helium nuclei?

Ernest Rutherford proved that alpha particles are helium nuclei through a collaborative effort at the University of Manchester. Working with his student Thomas Royds, Rutherford utilized the expertise of the laboratory's glassblower to isolate alpha particles. By performing a spectrochemical analysis on the isolated particles, they were able to demonstrate that the alpha particles were, in fact, helium ions.1