Rebecca Washenfelder

Research Chemist

Tropospheric Chemistry

NOAA Chemical Sciences Laboratory
325 Broadway, R/CSL7
Boulder, CO 80305 USA




The focus of my research is developing new laboratory and field instruments to measure trace gases and aerosol in the atmosphere. I have used cavity enhanced spectroscopy to measure glyoxal (CHOCHO), nitrous acid (HONO), nitrogen dioxide (NO2), formaldehyde (HCHO), and other gases. This is a sensitive and accurate technique that can achieve effective pathlengths of many kilometers in a cell with a physical length of 1 m.
Most recently, I am examining aerosol optical properties and absorbing organic aerosol ("brown carbon") using cavity enhanced spectroscopy and a particle-into-liquid sampler coupled to a liquid waveguide capillary cell (BrC-PILS). Wildfires are a major source of brown carbon, and I deployed the BrC-PILS instrument on the NOAA Twin Otter aircraft during FIREX-AQ in 2019.


B.A., Chemistry, Pomona College, 1999
M.S., Environmental Science and Engineering, California Institute of Technology, 2002
Ph.D., Environmental Science and Engineering, California Institute of Technology, 2006


- Measurement of aerosol optical properties and reactive trace gases using spectroscopic techniques.
- Quantifying the chemical and optical properties of organic aerosol.
- Information about my graduate work: column concentrations of greenhouse gases and the Total Carbon Column Observing Network.

Current Topics

Broadband cavity enhanced spectroscopy (BBCES) is an analytical technique that was first described by Fiedler et al. (2003). This approach uses a broadband light source, optical cavity, and grating spectrometer to acquire spectra with a very long effective absorption pathlength. Spectral fitting methods can be used to retrieve multiple absorbers. I have used this technique for laboratory and field measurements of glyoxal (CHOCHO), nitrous acid (HONO), nitrogen dioxide (NO2), ozone (O3), hydrogen peroxide (H2O2), and aerosol optical extinction.

I am currently focused on methods to determine complex refractive indices of aerosol in the ultraviolet spectral region. This is important because organic aerosols have been shown to absorb light in this spectral region, which may significantly affect the earth's radiative budget.

National Oceanic and Atmospheric Administration

last modified: August 05, 2021