Investigation of an energy-gap model for photoacoustic O2A-band spectra: H2O calibration near 7180 cm−1

► We investigate an energy transfer model for photoacoustic measurements of the O2A-band. ► We measure the response of a photoacoustic spectrometer for known quantities of H2O and O2. ► We fit multiple theoretical spectral line profiles to the data. ► We bind the relative uncertainty of the energy transfer model to less than 1%. ► We demonstrate that speed-dependence is an important line shape effect for these experiments.