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Firefly
The setup includes a cell containing the photoexcited gas-phase molecules and the FIREFLY (spectrometer dedicated to the measurement of weak IR emission signals). The FIREFLY spectrometer holds narrow bandpass interference circular variable filters, replicated from the ISOCAM instrument onboard of the ISO satellite (1996-1998). The filters have a high transmission (75% at 3.3 μm) and a moderate resolving power (λ/δλ = 45 at 3.3 μm). Specific ellipsoidal mirrors shape the collected IR beam to the desired dimensions on the filter and on a liquid nitrogen-cooled InSb detector (InfraRedAssociates). Its signal is amplified through a 1.5 Hz−20 kHz preamplifier before being digitized and recorded via a computer. The instrument was spectrally calibrated using gaseous ethanol, benzene, and CO2 absorption from a blackbody IR source. The reproducibility of the measurements of IR wavenumbers was characterized to be within 4 cm−1. The Firefly spectrometer can be coupled to the Nanograins set up.
