Tuesday 5 May, 1998 at 2pm

G. C. Sloan - Australian Defence Force Academy

"The nature of organic molecules in the interstellar medium"

ABSTRACT:"Since the discovery of the unidentified infrared (UIR) emission features (at 3.3, 6.2, 7.7, 8.6, and 11.2 um) in 1973, a great deal of controversy has developed over their origin. Many carriers have been proposed, all made of organic material. Of these, polycyclic aromatic hydrocarbons (PAHs) represent the best model. This talk will concentrate on what the PAH model can tell us about organic material in the interstellar medium, and just as significantly, what it cannot. The UIR features arise only from regions exposed to strong UV fields, and organic material in more shielded regions may have a very different structure. Long-slit infrared spectroscopy of extended regions of UIR emission such as the Orion Bar and NGC 1333 provides insight into both the structure of PAHs and the more protected organic material nearby."