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:

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

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

Expect some constant Breit-Wigner Resonance Curve

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

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

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

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

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).]

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

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