For decades, NASA scientists had tried to match the infrared emissions from carbon chemicals called Polycyclic aromatic hydrocarbons (PAH) to a mysterious infrared glow released by certain stars. The scientists never did find the right match, but in the course of their research, they built up a database of PAH signatures unmatched anywhere in the world.
Now NASA has put that PAH database online, opening up a cornucopia of new information on these cosmologically, biologically and commercially important carbon compounds.
"Initially, our hope was to help interpret the experimental spectra, but over time, our computational capabilities made it possible to study molecules much larger than can be studied in the laboratory," said Charles Bauschlicher Jr., a computational chemist at NASA’s Ames Research Center, in Moffett Field, Calif.
It's the world's largest collection of PAH infrared data, and the website contains nearly 700 spectra of PAHs in their neutral and electrically charged states. In addition, it has tools to download PAH spectra ranging in temperature from minus 470 to 2,000 degrees Fahrenheit (243 to 1,093 degrees Celsius). Thanks to these spectra, PAHs are now known to be abundant throughout the universe, but in exotic forms not readily found on Earth.
NASA tried to make the website user friendly for researchers, and the interface visually resembles the Google homepage. One can explore the database by charge, composition and spectral signatures. Tools allow users to do analyses online. For example, spectra can be combined to create a "composite" signature that can be compared directly to the spectrum of "unknown" material.
"PAHs in space are probably produced by carbon-rich, giant stars. A similar process produces soots here on Earth," said Louis Allamandola, an astrochemist at NASA's Ames Research Center.
"Besides astronomical applications," he said, "this PAH database and software can be useful as a new research tool for scientists, educators, policy makers, and consultants working in the fields of medicine, health, chemistry, fuel composition, engine design, environmental assessment, environmental monitoring, and environmental protection."