top of page
Hear your absorption

A direct way of measuring the aerosol absorption coefficient using the photo acoustic effect. Measurements at up to four wavelengths enable a specific characterisation of the aerosol.

  • Quantification of PM1 combustion aerosol, including black and brown carbon mass concentrations

  • Aerosol ageing processes under complex urban conditions

  • Source apportionment studies for light absorbing particulate matter from fossil fuel and biomass burning

  • Air quality monitoring networks

  • Detection limit better than 0.5 Mm  (equivalent to a black carbon concentration (eBC) below 0.05 µg m  )

  • Customisable wavelength combinations in the 375 nm to 785 nm spectral range

  • Separate optics, electronics, and flow units for flexible adaptation to your lab environment or implementation of accompanied measurements 

  • Fully integrated into 19” rack enclosures ready to be integrated in air-quality monitoring stations





Detection limit

Accuracy & Precision

Laser Beam

Laser Wavelengths

Acoustic resonator

Sample flow rate

Cell volume

Time resolution

Control Unit

Instrument Computer


Power Consumption*

Physical Dimensions


Specific measurement of the aerosol absorption coefficient of PM1 aerosol in a single photoacoustic cell at multiple (up to four) wavelengths


0.5 Mm  (approx. 0.05 µg m  Black Carbon)

10% and 3%

Up to four wavelengths efficiently combined to a 0.7 mm (1/e ) collimated beam

Customisable wavelength combinations in the 375 nm to 1550 nm spectral range (e.g. 405 nm, 515 nm, 660 nm, 785 nm) 

Compact stainless steel cylindrical cavity with a fundamental acoustic frequency of 3200 Hz

0.5 - 2 lpm

236 cm  (including acoustic buffer volumes)

1s sampling rate. 60s typical averaging time per wavelength.

Dual core (667 MHz) real time embedded controlle

2.0 GHz CPU, 4 GB RAM, 120 GB SSD Panel PC with 8” touch screen

Graphical data acquisition software. SQL database storage for long-term monitoring

180 W typical 

Optics Unit:        462 mm x 422 mm x 210 mm

Electronics Unit: 496 mm x 449 mm x 310 mm

Flow Unit:           436 mm x 449 mm x 177 mm

Optics Unit: 27 kg

Electronics Unit: 17 kg

Flow Unit: 5 kg






Laser 1

Laser 2

Laser 3

Laser 4

lock-in amplifier

photoacoustic cell

beam dump

power measurement

aerosol in

aerosol out

Schematic diagram of the PAAS-4λ measurement setup

Sample aerosol is led through the photoacoustic cell of the instrument. This cell consists of a cylindrical cavity that has a fundamental acoustic resonance frequency of 3200 Hz...


Schnaiter, F. M., Linke, C., Asmi, E., Servomaa, H., Hyvärinen, A.-P., Ohata, S., Kondo, Y., and Järvinen, E.: The Four-Wavelength Photoacoustic Aerosol Absorption Spectrometer PAAS-4λ, Atmos. Meas. Tech. Discuss. [preprint],, in review, 2023.

Schnaiter, M., Linke, C., Ibrahim, I., Kiselev, A., Waitz, F., Leisner, T., Norra, S., and Rehm, T., "Specifying the light-absorbing properties of aerosol particles in fresh snow samples, collected at the Environmental Research Station Schneefernerhaus (UFS), Zugspitze.", Atmospheric Chemistry and Physics, 19, 10829-10844, 2019, doi:10.5194/acp-19-10829-2019.

Linke, C., Ibrahim, I., Schleicher, N., Hitzenberger, R., Andreae, M. O., Leisner, T., and Schnaiter, M., "A novel single-cavity three-wavelength photoacoustic spectrometer for atmospheric aerosol research", Atmospheric Measurement Techniques, 9, 5331-3346, 2016, doi:105194/amt-9-5331-2016.

bottom of page