• Introduction and Background• Introduction and Background
For average stars like our own sun, the end of the stellar lifecycle is neither spectacular nor sudden. Instead, this stage is marked by a gradual decline in the star’s ability to produce the energy it needs to sustain itself and a steady deterioration of its structure. After swelling to many times its original size in the familiar “red-giant” phase, the star throws off its outer layers into the surrounding interstellar medium. During this tumultuous period, carbon produced deep within the heart of the failing star is dredged up and thrown out as well. It is in this outflow that copious quantities of polycyclic aromatic hydrocarbons (PAHs) and other carbon-rich materials are formed. For a while, the intense radiation from the remaining lifeless - but still fiercely hot - core of the former star lights up this shell of matter, producing a visually stunning “planetary nebula”. Eventually though, this glowing shell of matter fades and disperses into the tenuous diffuse interstellar medium that permeates our galaxy. In this manner, the interstellar medium is seeded with carbonaceous compounds.
I am an infrared spectroscopist specializing in the relatively new field of astrochemistry. Although I have always considered myself first and foremost a chemist, I have long been fascinated by the exotic and complex chemistry found in space. This interest led me to pursue my Ph.D. in physical chemistry with a minor in astronomy from Cornell University. After completing my degree, I was awarded an NRC Postdoctoral Associateship in the Astrochemistry Lab Group at the NASA Ames Research Center to continue my research in molecular astrophysics. In 1994, I returned to my home state of Michigan to accept a faculty position in the Chemistry Department at my undergraduate alma mater Adrian College - a small Liberal Arts college in southeastern Michigan. There I taught both General and Physical Chemistry courses. I remained in that position until 1997 when the opportunity arose to return to NASA Ames and the Astrochemistry Laboratory as a Space Scientist. Here are my publications.
• Research Interests
In general, our research efforts are directed toward the development of new experimental techniques to generate and study the infrared spectroscopic properties of PAHs, PAH ions, and related materials. Based on nearly two decades of research, it is now widely believed that such species are prevalent throughout the interstellar medium and are responsible for the so-called "Unidentified Infrared Bands" - a family of discrete interstellar infrared emission features dominated by bands at 3.3, 6.2, 7.7, 8.6, and 11.2 µm. Nevertheless, proper testing of the PAH model and exploitation of PAHs as interstellar probes has for some time been hampered by a general lack of knowledge of the spectral properties of these species in their likely interstellar forms: gas-phase, neutral and ionized molecules; clusters; and amorphous carbon particles. Thus, the overriding goal of our research activities in this area is the development of a comprehensive database of the infrared spectroscopic properties of a broad range of PAH species, covering different ionization states, different structural units, and derivatization with additional hydrogen, oxygen, and nitrogen - all measured under simulated interstellar conditions. To date, this database is comprised of nearly 60 discrete species representing neutral PAHs as well as positive and negative PAH ions. A substantial portion of our PAH database is currently available on line, and will continue to be updated in the future. In addition, we enjoy an active and very fruitful ongiong collaboration with Dr. Charles Bauschlicher of the Computational Chemistry Branch at NASA Ames and Dr. Stephanie Langhoff at NASA Ames. The spectral database resulting from their theoretical studies of a wide range of PAH species - some of which have been studied experimentally, some of which have not - is also available on line.
In our infrared laboratory studies, we employ the matrix isolation technique to trap our species of interest in a solid, noble gas matrix at cryogenic temperatures while it is probed spectroscopically. Although it may at first not be apparant, spectroscopic measurements under such conditions are directly relevant to the astrophysical problem.
Currently active research projects include:
Another aspect of our research in this area is the application of our laboratory data to the interpretation of astronomical infrared emission spectra. Most recently we have been collaborating with Prof. A.G.G.M. Tielens of the University of Groningen (The Netherlands) and his group on the detailed analysis of astronomical data measured using the European Space Agency's Infrared Space Observatory (ISO). Future NASA missions of direct importance to our work include the Stratospheric Observatory For Infrared Astronomy (SOFIA) and the Next Generation Space Telescope (NGST).
• Extracurricular Interests and Activities
Outside of work, I enjoy spending time with my wife, Mikki, and our four kids Brittany, Ian, Nathan, and Ellie.
In addition to my professional interest, I am also an avid amateur astronomer and telescope maker. In fact, it was my love of astronomy that originally led me to pursue a professional career in the field. You can click here for a picture of my old home-built 17.5" Dob telescope taken on an observing trip to my favorite dark-sky observing site, Lake San Antonio in southern Monterey county. For my thoughts on Lake San Antonio as an observing site, click here. This site is now the home of the newly organized California Star party - CalStar. My 17.5" scope was decommission a couple of years ago to make way for a larger 24" scope that just came on line this past fall.This scope has been decomissioned and has been replaced by a new 24" truss-tube dob. as I am now working on a larger 24" scope that I hope will be on line in time for the CalStar 2000 Star Party that will be held at Lake San Antonio in late September.
I also enjoy homebrewing (and drinking!) my own beer.
I am always happy to communicate with interested individuals and can be contacted by phone at (650) 604-4216, by Fax at (650) 604-6779, via e-mail, or by post at M/S 245-6, Moffett Field, CA 94035-1000.
Information about my Chemistry 161B class at San Jose State University can be found here.
Updated January 2001. Do you have any questions about this web site? Feel free to contact us.