Radical species in the Atmosphere: Detection and Investigation using Comb-based Absorption Laser Spectroscopy – RADICALS

Reactive radical traces play a fundamental role in atmospheric chemistry and the determination of radical concentrations is today an important challenge. We will address the ambitious goal of detecting these species directly in the atmosphere by developing absorption spectrometers with high sensitivity over a large spectral range. We will use frequency comb lasers to perform long-path detection without losing the coherence of the light, enabling precision spectroscopy and unambiguous quantification of multiple species simultaneously. The specific target will be the gas-phase traces of key radicals such as IO, BrO, NOx, CH3, NO3, HO2, HONO, and formaldehyde. We will develop and test comb-based complimentary long-path techniques: i) single laser dual-comb spectroscopy (DCS), and ii) Fourier transform spectroscopy (FTS); in complementary spectral range: i) in the visible, near-ultraviolet (UV) range and ii) in the mid-infrared (IR). These techniques will be employed to demonstrate simultaneous multi-species atmospheric monitoring.