Over 30 years have passed since polycyclic aromatic hydrocarbons (PAHs) were first proposed as the carrier of the previously unidentified infrared emission features.  These features can dominate the infrared spectra of objects as varied as planetary nebulae, star-forming regions, and starburst galaxies.  Since its introduction, the PAH model has gained widespread acceptance, but at the same time we have realized that PAHs are only the tip of the iceberg for interstellar carbon.  They appear almost as the last gasp of more fragile aliphatic structures which are destroyed first as ionization fronts around hot stars eat into the dust and molecular clouds around them.  Mixing aliphatic hydrocarbons with PAHs shifts the wavelengths of the spectral emission features in the laboratory, and we see these shifts in interstellar environments excited by cooler radiation fields.  Objects associated with aliphatic hydrocarbons include highly evolved stars which have not yet become planetary nebulae.  Many features in their spectra remain unidentified, and those features may hold the key to understanding the forms interstellar carbon takes in more benign environments.  Future progress depends on work in the laboratory and by theorists.

Polycyclic aromatic hydrocarbons and related forms of interstellar carbon

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.