Abstract

Near- to mid-infrared spectra of 17 Galactic Planetary Nebulae (PNe), which show prominent C-rich dust features, were obtained with the AKARI/IRC and Spitzer/IRS. Relative intensities of Polycyclic Aromatic Hydrocarbon (PAH) features were measured. The evolutionary stage of PNe is estimated by the effective temperature of the central star. The evolution of the PAH emission is investigated in terms of the evolution of the central stars. As PNe evolve, the ionization fraction of PAHs decreases, the 3:4–3:5mm aliphatic features become stronger and the peak position of the 6:2mm feature moves toward shorter wavelengths. Possible mechanisms for the evolution of the PAH emission are discussed.

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