Activity 2: Determining the value of a_A

Now that we know what a_V should be, we can move on to determine the asymmetry term (a_A) based on the shape of the binding energy curve across all of the oxygen isotopes, shown in the graph below.

Table 1 shows the parameters for the Liquid Drop (LD) formula. The sliders allow you to alter the constants. These changes will be reflected in Graph 1. Note that the values for a_S and a_C are already given.

Graph 1 shows the experimentally measured and theoretically calculated binding energy per nucleon for all observed isotopes of oxygen (from Table 2 on the previous page).

2(a) :: Vary the constant (a_A) in Table 1 until the shape of the theoretical binding energy curve matches the experimental data in Graph 1 as well as possible. We suggest you start by exploring what happens when you change the asymmetry parameter in steps of 5 MeV from 0 to 30 MeV. Note that you will not be able to get a perfect match.

2(b) :: Leave your answer for a_A in the Table to use it for the next activity. You might also want to make a note of your value to discuss in the FutureLearn course.