Activity 3: Investigating the effect of aP
Now that you have determined both aV and aA, we can investigate the effect of the pairing term (aP).
Graph 2 shows the difference between the experimentally measured and theoretically calculated binding energies (last column in Table 2, shown previously), using the current model parameters (from Table 1). If you have optimised aV and aA correctly, the line should be close to zero.
| Symbol | Value |
|---|---|
| aV | |
| aS | 18.3 |
| aC | 0.714 |
| aA | |
| aP | |
3(a) :: Keeping aV and aA at your optimised parameters (filled in from activities 1 and 2), set the pairing term (aP) to zero. In Graph 2, you should now see a ‘stepping’ effect depending on whether there is an odd or even number of neutrons in the oxygen isotope with masses 13 to 17. This is the effect of the pairing term.
What is the scale of the stepping you see in graph 2?
keV
You might also want to make a note of your value to discuss in the FutureLearn course.
3(b) :: Return aP to 12 MeV. You should find that the ‘stepping’ is now minimised.