Lecture 11b Polyatomic ideal gas Model - translation, rotation, vibration Rotational partition function Vibrational partition function - harmonic oscillator Thermodynamic functions Problems

Single polyatomic molecule Translational, rotational, vibrational and electronic energies additive qt - evaluated last lecture qr and qv - will evaluated today Typically with De - binding energy

Translation Consider a single diatomic molecule is the box M =m1+m2

Rotation Rotation energies: Degeneracy r is the rotational temperature

Rotation - continuation Unless temperature is very low: If two atoms are the same we overcounted states by  - symmetry number

Vibrations Vibrations - harmonic oscillator - frequency Near potential minimum With reduced mass

Vibrations - continuation Partition function Vibrational temperature

Partition function Q and free energy F translation rotation vibrations electronic

Energy translation rotation vibrations electronic

Heat capacity Translation rotation vibrations

Chemical potential