Molecules in planetary nebulae

Abstract

Circumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately merge with the ISM. Thus the study of PNe is the key to understand the transition from stellar to interstellar materials. The gas-phase molecules synthesized in CEs are believed to be the precursors of complex organic compounds. Strong ultraviolet radiation from PN central star can heavily photoionize, photodissociate or process molecules, resulting in different molecular compositions during the AGB-PPN-PN evolution. The discoveries of C60 and C60+ in circumstellar and interstellar environments suggest that large molecules can survive in PNe and enrich the ISM. In this presentation I shall briefly review some recent radio and infrared observations of molecules in PNe. Circumstellar chemistry and its link with interstellar matters will be discussed.