Poster abstract details

We carry out plasma diagnostic analysis for a number of planetary nebulae (PNe) and H II regions. We use N II and O II optical recombination lines (ORLs) with new effective recombination coefficients calculated under the intermediate coupling scheme, for a range of electron temperatures ($T_{e}$) and densities ($N_{e}$), and fitted against the most reliable measurements. Comparing $T_{e}$ derived from ORLs, collisionally excited lines (CELs), the hydrogen Balmer Jump, and/or He I if avaiable, we find the relation $T_{e}$ (ORLs) $<$ $T_{e}$ (He I) $<$ $T_{e}$ (H I BJ) $<$ $T_{e}$ (CELs), confirming the physical conditions in the two-abundance model postulated by Liu et al. (2000), i.e. the nebula contains another cold, metal-rich and probably H-deficient component.