Search for Λ-doubling Transitions of SiH in Orion Kleinmann-Low

A recent submillimeter line survey of Orion KL claimed detection of SiH. This Letter reports on GBT observations of the 5.7 GHz Λ-doubling transitions of SiH in Orion. Many recombination lines, including C164δ, are seen, but SiH is not detected. The nondetection corresponds to an upper limit of 1.5 × 1015 cm-2 (4 σ) for the beam-averaged column density of SiH. This suggests that the fractional abundance of SiH in the extended ridge is no more than twice that in the hot core.