= Solution
The <partial decay width> $\Gamma_x$ is the <energy> width associated with decay of the <compound nucleus> back into the entrance channel $x+X$; by <time reversal> it also controls formation from that channel. The <partial decay width> $\Gamma_y$ describes the selected exit channel $y+Y$. The total <decay width> sums all energetically accessible channels, including these: $\boxed{\Gamma=\sum_i\Gamma_i=\hbar/\tau}$. The <branching fraction> for channel $i$ is $\Gamma_i/\Gamma$. Widths have <energy> units, whereas $\Gamma_i/\hbar$ is a decay probability per unit time. The isolated-resonance formula assumes approximately constant widths over the resonance and neglects a nonresonant interfering background.
Back to article page
