# Professor Marissa Weichman (Princeton) "Precision Cavity-Enhanced Spectroscopy for Astrochemistry and Atmospheric Science" #### calendar\_today Date and Time **February 18, 2026** 04:00PM - 05:30PM EST #### pin\_drop Location **Haller Hall - 24 Oxford Street** [24 Oxford Street Cambridge, MA 02138 United States ]() *"Precision Cavity-Enhanced Spectroscopy for Astrochemistry and Atmospheric Science"* Light beaming to us across space encodes features arising from the absorption and emission of photons by a menagerie of interstellar molecules. Identification of these astrochemical species is key to understanding the chemical underpinnings of star, planet, and galaxy formation and the prebiotic origins of life. Interpretation and assignment of observational data has historically been driven by laboratory spectroscopy, though resolving individual quantum states in large molecules − even those with as few as 20 atoms − remains a challenging endeavor on the brink of treatment with our existing toolkit. As it becomes clear that astrophysical environments are brimming with complex, spectroscopically-challenging species, we must develop next-generation methods with improved resolution, sensitivity, and scope. Cavity-enhanced frequency comb spectroscopy simultaneously permits excellent spectral resolution, high sensitivity, and broadband readout − all essential for detailed spectroscopy of large gas-phase molecules. This technique centers around the use of frequency combs: light sources that emit a spectrum consisting of thousands of narrow, evenly-spaced “comb teeth” which act as many individual stable lasers lasing synchronously. We match the comb's spectral lines to the resonant modes of an optical cavity containing the molecular absorber of interest. The cavity dramatically increases the pathlength of light through the sample, yielding sensitive absorption spectra with broadband detection across the comb spectrum. My lab has recently commissioned a state-of-the-art cavity-enhanced comb spectrometer operating in the long-wave mid-infrared. Building on my prior work on the C 60 fullerene − by far the largest and highest-symmetry molecule for which a fully quantum-state-resolved spectrum has been reported – we are now extending comb spectroscopy to achieve a similarly clear picture of the quantum states of a library of polycyclic aromatic hydrocarbons and fullerenes likely to survive in harsh astrochemical environments. We will directly compare our measured spectra to observational data with the aim of identifying specific molecular carriers of interstellar features and unlocking new astrochemical assignments. Time-permitting, I will also touch on my group’s parallel efforts to advance laboratory methods for atmospheric aerosol science. Aerosols – particles and droplets between 10 nm and 10 µm in diameter – are among the largest sources of uncertainty in models of Earth’s climate through their direct interactions with solar radiation and indirect impacts on clouds. Studying isolated single aerosols in the laboratory allows us to directly correlate particle size and composition with optical properties, microphysics, and chemistry. We have recently commissioned a new single-particle electrodynamic balance in which we can trap and levitate individual aerosols, and interrogate them with cavity-enhanced spectroscopy and Mie scattering. We are working towards understanding how aerosols are transformed during their atmospheric residence times via processes like chemical aging, photobleaching, wetting, and icing. See also:- [ Forums ](/events/forums) Share on:- [ Facebook ](#) - [ Twitter ](#) - [ Linkedin ](#) Save: [ Add to calendar calendar\_today ](https://origins.harvard.edu/node/1629121/event-feed.ics) Copy link link