Download Stuff for Friday, May 4, 2012

Stuff for Friday, May 4, 2012
Midterm returned up front. (Also pick up old stuff!)
No quiz this week!
Stuff about nuclei and radioactivity:
Nuclei: AZ X where A nucleons = Z protons + N neutrons
Radius: r ≈ r0 A1/3 with r0 = 1.2 fm
1 u = atomic mass unit ≡
1
12 (mass
closest α: rmin = k (2e)(Ze)/K0
of
12
6 C)
= 931.48 MeV/c 2
mp = 1.007277 u mn = 1.008665 u me = 0.0005486 u
Binding energy Eb ≡ Eparts − Esystem ,
∆m ≡ mparts − msys = Eb /c 2
nucleus: ∆m = Z mH + Nmn − matom where mH = 1.007825 u
Stability: Can the nucleus lower its energy by radioactive decay?
Decays: alpha, beta (neutron β − , proton β + , EC) =⇒ ν or ν, gamma
Unstable nuclei
Check Table of Nuclides (google, e.g., http://atom.kaeri.re.kr/)
Binding energy calculation:
(6*1.007825u + 9*1.008665u − 15.0105993u)*931.48 MeV/u = 106.501 MeV
Coulomb Energy
Symmetry Energy