Professor Steven T. Shipman of New College of Florida is supported by the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry (with co-funding from the Division of Astronomical Sciences) to study the spectroscopy of "interstellar weeds" - molecules (such as methyl formate or dimethyl ether) that are relatively abundant in the interstellar medium (ISM). The dense and unpredictable spectra of these "weeds" generally frustrate attempts to identify new molecules in the ISM. The objective of this research is to obtain high-quality rotational spectra of these compounds at room temperature. These results will lead to better predictions of weed transition frequencies, significantly aiding astrochemists in the search for new complex molecules in the ISM.
Undergraduate students involved in this project will be directly participating in research addressing fundamental questions about the origins of complex molecules in the universe. As part of this work, they will gain experience in molecular spectroscopy, computational chemistry, and the construction of scientific instrumentation in a tight-knit academic environment that fosters close interactions between students and faculty mentors. Students will acquire experience crafting scientific arguments and communicating the results of their research to the broader scientific community. Educational impact will be enhanced by making the equipment available via cyber-access.
This award provided for the development and implementation of extended capabilities to the chirped-pulse microwave spectrometer at New College of Florida. These new bandwidth extension circuits have allowed us to nearly double the operating bandwidth of the spectrometer by increasing the maximum cutoff frequency from 18 to 26.5 GHz, allowing us to collect significantly more information about each molecule that we study with the spectrometer than was previously possible. These new capabilities were used to study a wide variety of molecules of potential astrochemical interest. In particular, we studied molecules similar to several "interstellar weeds". Interstellar weeds are molecules that are relatively small but which have very dense and complex spectra. The complexity of their spectra is generally due to the presence of large amplitude internal motion (such as from a methyl group with a low barrier to rotation) that can couple to the overall rotation of the molecules. Specific molecules that were studied with the newly-built equipment include ethyl mercaptan, 1-propanethiol, 2-propanethiol, 1-propylamine, 2-propylamine, 2-methoxyethanol, 2-ethoxyethanol, 2-aminobutanol, 3-methoxypropylamine, allyl bromide, methyl ethyl ketone, and methyl acetate. Our results from these studies have been presented as papers in various journals and as presentations at various conferences. The ethyl mercaptan results in particular have been used to help find this molecule in interstellar space. As new, more sensitive radio telescopes are developed and come online, we anticipate that our results will be used to guide searches for these compounds and will ultimately help to address fundamental questions about the origins of complex molecules in the universe. All of the work performed under this award was carried out by undergraduate students under the direction of the PI. The participating students gained experience in molecular spectroscopy, computational chemistry, and software and hardware development for scientific research. These students were also responsible for preparing and presenting talks and posters at conferences, and so gained experience in crafting scientific arguments and communicating the results of their research to the broader scientific community.