  We measured the branching fractions for the decay of the 5p 2 P 1/2 state of
88 Sr + by applying a recently demonstrated photon-counting sequential method
(M. Ramm et al., Phys. Rev. Lett. 111, 023004) to a single ion laser-cooled in
a micro fabricated surface trap. The branching fraction for the decay into the
5s 2 S 1/2 ground level was found to be p = 0.9453 +0.0007 --0.0005. This
result is in good agreement with recent theoretical calculations but disagrees
with previous experimental measurements, however affected by a one order of
magnitude larger uncertainty. This experiment also demonstrates the reliability
and the performances of ion micro trap technology in the domain of precision
measurements and spectroscopy. PACS numbers: 32.70.Cs, 06.30.Ft, 37.10.Ty
