LS coupling

LS coupling, also known as Russell-Saunders coupling, is a method used in physics to describe the total angular momentum of atoms, particularly for lighter elements. It approximates the total angular momentum of an atom as the vector sum of its total orbital angular momentum and its total spin angular momentum.1

• Orbital Angular Momentum: This arises from the motion of electrons around the nucleus and is quantized, meaning it can only take specific values.12
• Spin Angular Momentum: This is an intrinsic property of electrons, behaving as if they are spinning, which also creates angular momentum.32

This coupling scheme is useful when magnetic interactions between electrons are weak. For heavier atoms, a different scheme called jj coupling may be more appropriate. Spin is a fundamental property of subatomic particles, classifying them as either fermions (half-integer spin) or bosons (integer spin).12