Helmholtz resonator enhancement of photoacoustic signals

A Helmholtz resonator attached to a nonresonant photoacoustic cell enhances the responsivity to trace gas absorption by as much as a factor of 15.3. A simple system model based on a lumped parameter approach predicts the experimentally determined resonance frequency f(0) within 6% for all five resonator volumes tried and gives a pressure amplitude response at resonance proportional to f(0)(-5/2), which is the approximate experimental dependence. Optimization of response based on the model shows a pressure amplitude dependence on a(1/2), the square root of the radius of the cylindrical tube connecting the cell and the resonator.