ULTRAVIOLET-SPECTRA OF QUENCHED CARBONACEOUS COMPOSITE DERIVATIVES - COMPARISON TO THE 217-NANOMETER INTERSTELLAR ABSORPTION FEATURE

QCCs (quenched carbonaceous composite) are amorphus carbonaceous materials formed from a hydrocarbon plasma. We present the UV-visible spectra of ''filmy QCC'' (obtained outside of the beam ejected from the hydrocarbon plasma) and ''dark QCC'' (obtained very near to the beam) for comparison to the interstellar extinction curve. When filmy QCC is heated to 500-700-degrees-C (thermally altered), the wavelength of the absorption maximum increases from 204 nm to 220-222 nm. The dark QCC has an absorption maximum at 217-222 nm. In addition, the thermally altered filmy QCC has a slope change at about 500 nm which resembles that in the interstellar extinction curve. The resemblance of the extinction curve of the QCCs to that of the interstellar medium suggests that QCC derivatives may be representative of the type of interstellar material that produces the 217 nm interstellar medium feature. The peak extinction of the dark QCC is higher than the average interstellar extinction curve while that of the thermally altered filmy QCC is lower, so that a mixture of dark and thermally altered filmy QCC can match the peak extinction observed in the interstellar medium. It is shown from electron micrographs that most of the thermally altered filmy QCC is in the form of small grainy structure less than 4 nm in diameter. This shows that the structural unit causing the 217-222 nm feature in QCC is very small.