An infrared filter radiometer for atmospheric cluster-ion detection.

Area of Science:

• Atmospheric Science
• Spectroscopy
• Instrumentation

Background:

• Infrared absorption bands from atmospheric cluster ions have been observed in laboratory settings.
• Detecting these ions in the atmosphere is crucial for understanding atmospheric processes.

Purpose of the Study:

• To develop and calibrate a narrowband filter radiometer for detecting atmospheric cluster ions.
• To assess the instrument's sensitivity and response to atmospheric ion fluctuations.

Main Methods:

• Construction of a narrowband filter radiometer with a 9.15 µm filter and auxiliary germanium filter.
• Laboratory calibration using a blackbody source to determine sensitivity.
• Field experiments to measure response to atmospheric ion changes.

Main Results:

• The filter radiometer achieved a laboratory sensitivity of (29.3±0.1) µV/(W m⁻²).
• The instrument demonstrated responsiveness to cluster-ion fluctuations in atmospheric experiments.
• Sensitivity to atmospheric ion changes was determined to be (0.47±0.05) (mW m⁻²)/(ions cm⁻³).

Conclusions:

• The developed filter radiometer is a viable tool for detecting atmospheric cluster ions.
• The instrument's sensitivity allows for the study of ion fluctuations in atmospheric conditions.
• This technology can advance atmospheric research related to ion chemistry and physics.