Vector atom model and coupling schemes

LS coupling and JJ coupling by Waqas Ali

1. Coupling L-S and J-J Coupling

2. Presented to: Dr. Waseem Ahmad Presented by: Muhammad Waqas Ali (Bsf1803653) Asmatullah chandia ( Bsf1803676) M. Shehbaz Qamar ( Bsf1803672) Muhammad Junaid ( Bsf1803664)

3. Table of Contents Vector Atom Model Coupling L-S Coupling J-J Coupling

4. Vector Atom Model Proposed by Uhlenbeck and Goudsmit in 1925,, extension to Bohr- Sommerfield model just after De Broglie hypothesis S pace quantization and spinning electron hypothesis Electrons have spins around their axis, have magnitude Electrons revolve around the nucleus in orbits having orbital angular momentum, having magnitude Total angular momentum= J = L + S Semi-classical Model 3D model, 2 dimensions define the size and form of electron while 3 rd one defines quantization of electron orbit. Only certain discrete orientation of e-orbit are allowed  

5. Vector Atom Model

6. Atom having an electron cloud around nucleus, say 3D space. Electron’s positive (clockwise, upwards) and negative spin (anti-clockwise, downwards)

7. Atomic Coupling? S pin–orbit coupling, also known as spin-pairing, describes a weak magnetic interaction, or coupling, of the particle spin and the orbital motion of this particle, e.g. the electron spin and its motion around an atomic nucleus.

8. L-S Coupling Also called as Russell-Saunders coupling Electron’s orbital angular momentum (L) and Electron spin (S) interaction T he orbital angular momenta of the individual electrons add to form a resultant orbital angular momentum More accurate than Bohr Model in energy and radius of atom Electrons have spins around their axis, have magnitude Electrons revolve around the nucleus in orbits having orbital angular momentum, having magnitude Total Angular Momentum will be LS Coupling lecture: https ://www.youtube.com/watch?v=kcvtKnDb3iY  

9. L-S Coupling Figures

10. J-J Coupling O ccurs between electrons in atoms and nucleons in nuclei In this scheme, each  electron n  is assigned an angular momentum  j  composed of its orbital angular momentum  l  and its spin  s T he energies associated with the spin-orbit interactions are much higher than the energies associated with electrostatic repulsion Multiplets of many-electron atoms having a large atomic number are characterized by j-j coupling S election rules for j-j coupling are, only one electron jumps at a time and the `-value of the jumping electron must change by one unit or, more generally, the parity must change The total angular momentum  J  is then the vector addition of  j 1  +  j 2  +  j 3  +…, where each  j n  is due to a single electron J-J Coupling lecture: https ://www.youtube.com/watch?v=5NUMaDY_GEo

11. J -J Coupling Figures