POSSIBLE DISCOVERY OF THE 70 MICRON H3O-)-]3(3)(+) TRANSITION IN ORION-BN-IRC2(4(3)()

We report the first astronomical detection of a far-IR emission line a t (69.524 +/- 0.008) mu m from aboard the Kuiper Airborne Observatory (KAO), We tentatively assign this line to the R-branch transition 4(3) (-) --> 3(3)(+) of H3O+. The wavelength of the discovered line lies be tween -112 and -60 km s(-1) from predicted values, The position at whi ch the emission line was detected is located about 20 '' north of Orio n BN, which is close to the shocked molecular hydrogen peak 1. We excl ude hot shocked gas as the possible origin of the H3O+ emission, Hydro gen densities of greater than or similar to 5 x 10(8) cm(-3) and tempe ratures greater than or similar to 100 K are required to match the obs erved integrated intensity of the 70 mu m line, A speculative explanat ion for the 70 mu m H3+O emission is that it might originate from very dense clumps.