On the internal kinematics of PNe

Our new sample of spectra of round/elliptical double-shell PNe around central stars (CSs) with H-rich surface chemistry covers all evolutionary phases across the HRD. By means of high-res. & high S/N spectra we determine bulk matter velocities of the inner wind-driven rims and the maximum (= post-shock) gas velocities of the surrounding thermally expanding shells. Studying the details of the internal kinematics allows a look at processes of PN formation & at PN expansion history helping, for instance, to determine expansion distances. Ralf Jacob1, Detlef Schonberner1, Holger Lehmann2, Alena Zwanzig1, Christer Sandin1, and Matthias Steffen1