SIMBAD references

Theoretical IR spectra of naphthalene derivatives, considered as models for small isolated PAHs have been obtained using ab-initio quantum mechanical calculations. The effects of separate and combined ionization and multiple dehydrogenation have been studied. Significant changes appear, especially in intensity, with respect to neutral naphthalene. The best match to the interstellar emission is obtained for the singly ionized, singly and doubly dehydrogenated species. These theoretical results confirm that PAHs present the structural characteristics to fit the still debated UIR bands. In the regions where they are observed, the small carriers should be mostly ionized but only partly dehydrogenated with a few triple bonds at the periphery of the carbon skeleton.