Hi! it's been a day since I have started this problem. I was wondering how I could arrive to this Hamiltonian? And I'm a bit at a lost on how exactly to derive this? I hope anyone can help me with this, even a suggestion of good starting point would be much appreciated. Basically the problem is to derive a hamiltonian for the system here. Regarding this, I'm currently thinking of having a set of polar and azimuthal terms cancel out and thus leading to this maybe? Thank you very much!