This work details an application of collinear resonance ionization spectroscopy for the separation of short-lived isomeric states and their subsequent study with decay spectroscopy. It reports the successful construction of a novel decay spectroscopy apparatus that can operate at pressures below 1 x 10 DEGREES-9 mbar. The method is demonstrated by separating the nuclear ground and isomeric states of 204Fr and performing alpha-decay spectroscopy. An equivalent mass spectrometer would require 4.6 million times as much resolution to achieve the same result. This work unambiguously confirms the...