Molecular relaxation effects on vibrational water vapor photoacoustic spectroscopy in air

Benjamin Lang*, Philipp Breitegger, Georg Brunnhofer, Jordi Prats Valero, Simon Schweighart, Andreas Klug, Wolfgang Hassler, Alexander Bergmann

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Photoacoustic spectroscopy is a highly sensitive technique, well suited for and used in applications targeting the accurate measurement of water vapor in a wide range of concentrations. This work demonstrates the nonlinear photoacoustic response obtained for water vapor in air at typical atmospheric concentration levels, which is a result of the resonant vibrational coupling of water and oxygen. Relevant processes in the relaxation path of water in a mixture with air, excited with near-infrared radiation, are identified and a physical model for the acoustic signal measured with a resonant photoacoustic cell is presented. The model is valid for modulation frequencies typical for conventional and quartz-enhanced photoacoustic spectroscopy and provides a simplified means of calibration for photoacoustic water vapor sensors. Estimated values for comprised model coefficients are evaluated from photoacoustic measurements of water vapor in synthetic air. Furthermore, it is shown experimentally that the process of vibrational excitation of nitrogen is of negligible importance in the relaxation path of water vapor and thus insignificant in the photoacoustic heat production in atmospheric measurement environments.

Original languageEnglish
Article number64
Number of pages18
JournalApplied Physics B: Lasers and Optics
Issue number4
Publication statusPublished - 1 Apr 2020

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Physics and Astronomy(all)


Dive into the research topics of 'Molecular relaxation effects on vibrational water vapor photoacoustic spectroscopy in air'. Together they form a unique fingerprint.

Cite this