Nuclear and Elementary Particles, Week 3 Tutorial B, 22th of Sep. 17.

In this Tutorial we discuss the outline of a semi-classical way to predict the decay rate of an alpha-emitting nucleus (for a more complete explanation: see video on alpha emission), and discuss its validity. We then go on to recap the Semi-Emperical Mass Formula (SEMF), and derive a condition to predict the stability of nuclei. We end by applying the SEMF for some real life cases.

COMMENT: when calculating the most stable isotope with mass number 111 I took the approximated form of the formula, which then yielded it to be Rh-111 ( Z = 45 ). However, for A = 111, the approximated formula is about 18% off the un-approximated form. If I had taken the un-approximated form, A = 111 would have yielded Ag-111 ( Z = 47 ), which indeed has a much longer half-life than Rh-111. As a final comment, measurements reveal that Cd-111 ( Z = 48) has the longest half-life of all
A = 111: this isotope is stable. The Semi-Empirical Mass Formula got us very close to the mark, but not the exact right isotope.