  We searched for Technetium (Tc) in a sample of bright oxygen-rich asymptotic
giant branch (AGB) stars located in the outer galactic bulge. Tc is an unstable
element synthesised via the s-process in deep layers of AGB stars, thus it is a
reliable indicator of both recent s-process activity and third dredge-up.
  We aim to test theoretical predictions on the luminosity limit for the onset
of third dredge-up.
  Using high resolution optical spectra obtained with the UVES spectrograph at
ESO's VLT we search for resonance lines of neutral Tc in the blue spectral
region of our sample stars. These measurements allow us to improve the
procedure of classification of stars with respect to their Tc content by using
flux ratios. Synthetic spectra based on MARCS atmospheric models are presented
and compared to the observed spectra around three lines of Tc. Bolometric
magnitudes are calculated based on near infrared photometry of the objects.
  Among the sample of 27 long period bulge variables four were found to
definitely contain Tc in their atmospheres.
  The luminosity of the Tc rich stars is in agreement with predictions from AGB
evolutionary models on the minimum luminosity at the time when third dredge-up
sets in. However, AGB evolutionary models and a bulge consisting of a single
old population cannot be brought into agreement. This probably means that a
younger population is present in the bulge, as suggested by various authors,
which contains the Tc-rich stars here identified.
