Measurements of the pressure shift of water vapor absorption lines by simultaneous photoacoustic spectroscopy

Simultaneous photoacoustic spectroscopy is introduced as a convenient and accurate method for the measurement of small absorption line shifts due to the pressure of the surrounding atmosphere. Results are presented for fourteen water vapor lines in the 725-nm spectral region. Rather large pressure shift coefficients of up to −0.040 cm−1/atm are observed, which have to be taken into consideration in remote sensing applications in which the exact positioning on the line center is critical, e.g., differential absorption lidar.