Isospin, or isotopic spin, is a quantum variable describing the relationship between protons and neutrons in nuclear and particle physics. (Strictly, it describes the relationship between up and down quarks, as described in Chapter 39, but it was introduced before the advent of the quark model.) It has the same algebraic properties as quantum angular momentum: A proton and a neutron form an iso-doublet ot states, with total isospin quantum number 1/2; the proton is in the t2 = 1/2 state, and the neutron is in the t2 = 1/2 state, where l refers to a direction in an abstract isospin space.
a) What isospin states can be constructed from two nucleons, that is, two particles with t = ½? To what nuclei do these states correspond?
b) What isospin states can be constructed from three nucleons? To what nuclei do these correspond?