Molecular Structure

Phase 3: Molecules and Spectroscopy

Syllabus Goal

Understand the Born-Oppenheimer approximation.

Born-Oppenheimer Approximation

Separation of nuclear and electronic motion due to the large mass difference ($M_N \gg m_e$).

1. Solve electronic Schrödinger equation for fixed nuclear positions.
2. Electronic energy serves as potential energy for nuclear motion.

Diatomic Molecules

• Electronic States: $\Sigma, \Pi, \Delta$ (based on $\Lambda$).
• Vibrational States: Harmonic oscillator approximation.
• Rotational States: Rigid rotor approximation.