Brett A. McGuire

Brett McGuire

During his PhD at the California Institute of Technology, Brett constructed a spectrometer to measure the far-infrared (THz) absorption spectra of interstellar ice analogs. Such ices may be the dominant source of complex molecule formation in the ISM, and yet their compositions are largely unknown due to the difficulty of characterizing them using known infrared spectra. The THz region of the spectrum, which overlaps well with the new SOFIA observatory’s capabilities, provides the opportunity for unambiguous observation and characterization of these ices once laboratory data are known.

As part of his postdoc, he transitioned into the microwave/mm/sub-mm region of the spectrum with high-resolution, gas-phase rotational spectroscopy of reactive or transient species. Rotational spectra are, in principle, completely defined by the three moments of inertia of a molecule. Thus, in addition to providing the spectral signatures needed for identifications in the ISM, the exact geometries of these species can be determined as well. In turn, when coupled with high-level ab initio calculations, these geometries provide the precise energetics of a system needed to robustly understand the formation pathways and mechanisms used in models of formation chemistry in the ISM.

He is also a member of a team of astronomers working to expand our knowledge of the gas-phase chemical inventories in the ISM through the Prebiotic Molecular Survey of the Sgr B2(N) star-forming region. As a result, he has published the first detection of propylene oxide (CH3CHCH2O), the first chiral molecule found outside our solar system, and carbodiimide (HNCNH) a new astronomical maser. Through observational programs such as this, which rely heavily on complimentary laboratory efforts, he hopes to shed light on the processes which can give rise to species such as glycine in the ISM.

Most recently, he led an effort which resulted in the first detection of an aromatic, benzene-ring containing molecule in the interstellar medium: benzonitrile (c-C6H5CN). It's thought that a class of interstellar aromatic benzene-ring molecules known as the polycyclic aromatic hydrocarbons (PAHs) contain ~10% of all the carbon in the universe. Due to their unique structural properties, however, it is extraordinarily challenging to observe them. Our detection of benzonitrile changes the game on this, and offers us the ability to study these types of molecules routinely, and without the need for the infrared space-based telescopes we have had to use (with limited success) until now. As part of his microwave spectroscopy work, he has undertaken a comprehensive follow-up program to study the formation of these ring structures from non-cyclic precursor molecules in the laboratory.