Molecular Physics

In this section, we will study the binding and excitation of simple molecules. Atoms bind into molecules by sharing electrons, thus reducing the kinetic energy. Molecules can be excited in three ways.

• Excitation of electrons to higher states. $E\sim$ 4 eV
• Vibrational modes (Harmonic Oscillator). Nuclei move slowly in background of electrons. $E\sim$ 0.1 eV
• Rotational modes ($L=n\hbar$). Entire molecule rotates. $E\sim$ 0.001 eV

Why don't atoms have rotational states?
The atomic state already accounts for electrons angular momentum around the nucleus.

About which axes can a molecule rotate?

Do you think identical atoms will make a difference?

This material is covered in Gasiorowicz Chapter 20, and in Cohen-Tannoudji et al. Complements $C_VI$, $E_{VII}$, $C_{XI}$.