The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases and aerosol extinction with a single instrument.

CE-DOAS relies only on the measurement of relative intensity changes, i.e. does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). The instrument is inherently calibrated for light extinction from the cavity by observing O4 and measuring the pressure and temperature independently. These cavities can be constructed from the UV through Red wavelengths to measure species such as: HONO, NO2, glyoxal, methyl glyoxal, IO, OIO, I2, H2O and NO3.

These optical cavities can be used in laboratory studies such as the CLOUD project, are designed to be portable in order to deploy in the field (Cal-NEX 2010) or taken to atmospheric simulation chambers. Current instrument developments include temperature controlled optical caivties (200-295K) for measuring absorption cross-sections of oxygen dimers and a fast flow cavity working at 2Hz to measure fluxes of glyoxal over the ocean (deployed during the TORERO field campaign).