Incoherent Broadband Cavity Enhanced Absorption Spectrometer (IBBCEAS)

The Incoherent Broadband Cavity Enhanced Absorption Spectrometer (IBBCEAS) is an in-house built instrument that is used to study nitrous acid (HONO) sources in outdoor and indoor environments. This instrument gives HONO and NO2 absorption information of the sample being studied. The IBBCEAS is comprised of an air-tight 70 cm Teflon tube that has inlet and outlet valves for the sample and holds highly reflective mirrors on both ends. On one end of the cavity is an LED as the light source which is collimated into the cavity using a combination of optics. The light is reflected back and forth in the cavity by the mirrors which results in a pathlength of about 1.4 kilometers. On the other end of the cavity, optics focus the light into a fiber optic leading to a CCD detector which measures light intensity. This data is deconvoluted to give absorption/concentration information of HONO and NO2 and allows for the simultaneous measurements of the two analytes. This capability is important because a significant source of HONO is the surface reaction between photosensitized humic acid and NO2. The types of samples that can be studied by the IBBCEAS are calibrated HONO/NO2 gases or the headspace of reactions that are carried out in a separate Teflon reaction cell in which a carrier gas (which may be key in the reaction) flows into the IBBCEAS inlet. This instrument can give insight into HONO sources in outdoor and indoor environments including photochemical and heterogenous chemistry.