AND

Absorption lines of have been detected in the spectra of two infrared sources in the GalacticH3`center and also toward the heavily reddened star Cygnus OB2 No. 12, whose line of sight is believed to include only diuse interstellar gas. The absorptions toward the Galactic center sources (IRS 3 and GCS 3-2) probably are due to both in diuse gas and in molecular clouds. The ratios of line equiva-H3 ` H3`lent width to extinction toward these three sources are much greater than those toward dense clouds where has been detected previously. Analysis of the spectra coupled with a simple model for theH3`abundance of in the diuse interstellar medium implies that the observed is present at low den-H3 ` H3`sities along long path lengths. These are the Ðrst detections of in the diuse interstellar medium.H3