Heat capacity of a diatomic gas
= Heat capacity of a diatomic gas
{title2=$C_V\longrightarrow7R/2$}
For an ideal diatomic gas with intact molecules and all translational, rotational and harmonic vibrational degrees of freedom active, the classical molar <heat capacity> is $7R/2$. Quantum freeze-out of vibrations and then rotations produces approximate $5R/2$ and $3R/2$ regimes. The model excludes dissociation, condensation and electronic excitation.