  We introduce the differential and the total decay widths of a resonant
(Gamow) state decaying into a continuum of stable states. When the resonance
has several decay modes, we introduce the corresponding partial decay widths
and branching fractions. In the approximation that the resonance is sharp, the
expressions for the differential, partial and total decay widths of a resonant
state bear a close resemblance with the Golden Rule. In such approximation, the
branching fractions of a resonant state are the same as the standard branching
fractions obtained by way of the Golden Rule. We also introduce dimensionless
decay constants along with their associated differential decay constants, and
we express experimentally measurable quantities such as the branching fractions
and the energy distributions of decay events in terms of those dimensionless
decay constants.
