  The Odin satellite has been used to search for the 118.75-GHz line of
molecular oxygen (O2)in the Galactic centre. Odin observations were performed
towards the Sgr A* circumnuclear disk (CND), and the Sgr A +20 km/s and +50
km/s molecular clouds using the position-switching mode. Supplementary
ground-based observations were carried out in the 2-mm band using the ARO Kitt
Peak 12-m telescope to examine suspected SiC features. A strong emission line
was found at 118.27 GHz, attributable to the J=13-12 HC3N line. Upper limits
are presented for the 118.75-GHz O2 (1,1-1,0) ground transition line and for
the 118.11-GHz 3Pi2, J=3-2 ground state SiC line at the Galactic centre. Upper
limits are also presented for the 487-GHz O2 line in the Sgr A +50 km/s cloud
and for the 157-GHz, J=4-3, SiC line in the Sgr A +20 and +50 km/s clouds, as
well as the CND. The CH3OH line complex at 157.2 - 157.3 GHz has been detected
in the +20 and +50 km/s clouds but not towards Sgr A*/CND. A 3-sigma upper
limit for the fractional abundance ratio of [O2]/[H2] is found to be X(O2) <
1.2 x 10exp(-7) towards the Sgr A molecular belt region.
