The quality factor of low-frequency oscillations in gases

Abstract

Measurements of the quality factor Q for damped oscillations in a modified Rüchardt's experiment for gases show two striking features. First, when Q is plotted as a function of the period of oscillation T (or the volume of gas), a maximum occurs at low values of T (small volumes). Second, values of Q_max for various gases span a range (∼8 to 75) which is typical for mechanical systems: in this sense one can classify heavily damped gases (e.g. He), medium damped gases (e.g. CO₂), and lightly damped gases (polyatomic gases). These features can be understood in terms of a model based on internal friction associated with heat flows in an oscillating confined gas, and provide clear evidence for the non-adiabatic nature of the oscillations.