New infrared absorption cross sections of difluoromethane (HFC-32) for atmospheric remote sensing

Difluoromethane (CH2F2; HFC-32), a hydrofluorocarbon (HFC) used as a refrigerant in air conditioning and heat pump systems, is currently being phased out under the terms of the Montreal Protocol (Kigali Amendment). In order to monitor its concentration profiles using infrared-sounding instruments, for example the Atmospheric Chemistry Experiment – Fourier transform spectrometer (ACE-FTS), accurate laboratory spectroscopic data are required. This work describes new high-resolution infrared absorption cross sections of difluoromethane / dry synthetic air over the spectral range 850–1335 cm−1, derived from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26-cm-pathlength cell. Spectra were recorded at resolutions between 0.009 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD = maximum optical path difference) over a range of temperatures and pressures (7.6–760 Torr and 188–297 K). The new absorption cross sections in this work improve upon those currently available in HITRAN for remote sensing.