  We identify emission lines of post-iron peak elements in very high
signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines
from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement
with the theories of s-process in AGB star. Surprisingly, we did not detect
lines from Br even though s-process calculations indicate that it should be
produced with Kr at detectable levels.
