features is correct, then about 1% of the elemental carbon is locked up in these 

 species. It is noteworthy that the carbonaceous grains in carbonaceous meteor- 

 ites also exhibit Raman spectroscopic features similar to those of figure 3-7. 

 These grains are also the bearers of isotopic ratios of D/H that approach those 

 ratios observed in interstellar molecules. 



10 



8.3 



Microns, |im 

 7.14 6.25 



5.55 



(a) Auto Soot-Raman 



A. 



/•' 



,1 



I 



1 



(b) Orion Bar-Emission 



20 



E 

 o 



ru 



<=> 10 



X 



Z5 



y 



w^ 



1000 1200 1400 



Wavenumbers, cm 



1600 



1 



1800 



Figure 3-7. Comparison of the Raman spectrum of auto soot, a collection of 



polycyclic aromatic molecules, with the 5- to 7 O-micrometer emission 

 features in the Orion bar. 



69 



