Vibrational motion

This chapter focuses on molecular vibration, which plays a role in the interpretation of thermodynamic properties. It introduces the ‘harmonic oscillator’, a simple but very important model for the description of vibrations. The chapter shows that the energies of an oscillator are quantized and that an oscillator may be found at displacements that are forbidden by classical physics. The energy levels of a quantum mechanical harmonic oscillator are evenly spaced. The chapter then explains how the wavefunctions of a quantum mechanical harmonic oscillator are products of a Hermite polynomial and a Gaussian (bell-shaped) function. A quantum mechanical harmonic oscillator has zero-point energy, an irremovable minimum energy.