A’ = A - 4
Z’ = Z - 2
Alpha Decay - Energy of alpha particle
Calculating mass defect of alpha decay U 232 --> Th 228 + Alpha
232.037131 --> 228.028716 + 4.002602
(Appendix F, for Alpha = He 4)
(#electrons?)
232.037131 --> 232.031318 (products have less mass)
Mass defect = parent - products = 232.037131 - 232.031318
= 0.005813 u
Ek = (0.005813 u)(931.5 MeV/u) = 5.415 MeV
(Less - daughter Ek)
H = 1.007825 u, Neutron = 1.008665 u, 1 u = 931.5 MeV
He (neutral atom) = 4.002602 u
Parent mass = 247.07030 u
Product mass = 243.061373 u + 4.002602 u = 247.063975 u
Mass defect = parent - products = 0.006325 u
Energy of radiation = (.006325 u)(931.5 MeV/u) = 5.892 MeV
= (5.892 x106 eV)(1.602 x 10-19 J/eV) = 9.439 x 10-13 J
24797Bk --> 24395Am + α
247.07030 --> 243.061373 + 4.002602
What is energy of alpha? (in MeV and J)
5.892 MeV, 9.439 x 10-13 J
Parent mass = 243.061373 u
Product mass = 239.052932 u + 4.002602 u = 243.055534 u
Mass defect = parent - products = 0.005839 u
Energy of radiation = (0.005839 u)(931.5 MeV/u) = 5.439 MeV
= (5.439 x106 eV)(1.602 x 10-19 J/eV) = 8.713 x 10-13 J
Ek = 1/2mv2, m = 6.64 x 10-27 kg, Ek = 8.713 x 10-13 J
v = 1.62 x 107 m/s
24395Am --> 23993Np + α
243.061373 -->239.052932 + 4.002602
(It’s a decay series!!!)
What is energy of alpha? (in MeV and J)
What is the velocity of the alpha? (m/s)
mα = 6.64x10-27 kg
5.439 MeV, 8.713 x 10-13 J, 1.62 x 107 m/s
Why Alpha Decay
Only possible if mass products < parent
Tendency to reduce potential energy
Larger nuclei
He nucleus is rather tightly bound
He Nucleus
Tunneling - Energy is not conserved!
Alpha shouldn’t escape (energy)
ΔEΔt > h/2π
Violates COE (briefly)
“Tunneling”
Pure quantum randomness
Ek of alpha - observed
Shape of curve
Capture of Alpha:
Repulsion - Coulombic
Attraction - Strong Nuc.
Ek(Alpha) < Ek(Capture)