1. probability of surviving
through at least time t
mean lifetime  = 1/
For any free particle (separation of space-time components)
Such an expression CANNOT describe an unstable particle
since
Instead mathematically introduce the exponential factor:

2. a decaying probability
then
a decaying probability
of surviving
Note: G=ħ
Also notice: effectively introduces an imaginary part to E

3. Applying a Fourier transform:
What’s this represent?
E distribution of
the unstable state
still complex!

4. Expect
some constant
Breit-Wigner Resonance Curve

6. 1.0 
MAX
0.5
 = FWHM E Eo
When SPIN of the resonant state is included:

7. 130-eV neutron resonances
Transmission
130-eV neutron resonances
scattering from 59Co
-ray yield for
neutron radiative
capture

8. +p elastic scattering cross-section in the region of the Δ++ resonance.
The central mass is 1232 MeV with a width =120 MeV

9. e+e- anything near the Z0 resonance plotted against cms energy
Cross-section for the reaction
e+e- anything
near the Z0 resonance
plotted against
cms energy

10. Cross section for the reaction B10 +   N14* versus energy.
The resonances indicate levels in the compound nucleus N14*.
[Talbott and Heydenburg, Physical Review, 90, 186 (1953).]

11. Spectrum of protons scattered from Na14 indicating its energy levels.
[Bockelman et al., Physical Review, 92, 665 (1953).]

12. Resonances observed in the radiative proton capture by 23Na.
[P.W.m. Glaudemans and P.M. Endt, Nucl. Phys. 30, 30 (1962).]