PAH DISTRIBUTION IN BD+30 3639

We present observations of the planetary nebula BD+30 3639 in the 3.3 mu m feature and nearby continuum. The dust envelope is clearly resolv ed as a circular shell surrounding the exciting star. The 3.3 mu m emi ssion correlates closely with the spatially resolved HII region, and a large fraction (similar or equal to 70%) of the feature emission dete cted is coming from lines of sight toward the ionized region. The feat ure emission has a diffuse component distributed all over the ionized ring with several maxima which may originate from neutral or protected condensations. The distribution of the 3.3 mu m feature and the conti nuum emission is analyzed to determine the variations of the emissivit y and abundance of the 3.3 mu m emitters under the PAH hypothesis. The abundance of the 3.3 mu m feature emitting particles is shown to rise steadily inside the ionized region toward the outer edge where it is maximum and 1 to 1.5 times that proposed by Desert et al. (1990) for t he diffuse ISM. Most of the PAH emitting the 3.3 mu m feature are loca ted outside the ionized shell but still, a significant fraction of the PAH (> 11%) is found inside the HII region. We discuss these results in the frame of the PAH model, with particular emphasis on the formati on and destruction of these molecules in the circumstellar environment . The comparison with the HII/MC interface in M17 indicates that PAH d estruction or alteration caused by the high radiation fields in HII re gions has to be balanced by faster recombination processes in the case of dense objects as BD+30 3639. Destruction through Coulomb Dissociat ion of PAH dications is consistent with the observations, if stability of large PAH dications is significantly larger than that of benzene. Dehydrogenation through Photo-Termo Dissociation may also explain the observed variations in BD+30 3639, provided relatively small PAH are p resent in the HII region (similar or equal to 20 C atoms). The PAH abu ndances derived appear to be low for this type of objects to provide d irectly a large fraction of the PAH observed in the ISM. The relevance of this result for the formation of PAH molecules in the ISM is discu ssed.