A SEARCH FOR THE 13 175-S-ANGSTROM INFRARED DIFFUSE BAND IN DENSE ENVIRONMENTS

Models of ionized interstellar C60 predict a strong transition in the 1.2-mum region, and two candidate bands have recently been detected in reddened stars. We have searched for the stronger of these bands (at 13 175 angstrom) in the Taurus dark cloud complex, to determine its response to the dark cloud environment. None of the three lines of sight studied (two near the cloud surface, one reaching A(V) > 20 mag) gives rise to a detectable band; in one case, the equivalent width is a factor of order three below that predicted. Since such behaviour is also shown by the optical diffuse interstellar bands (DIBs), we suggest that the 13 175-angstrom band is a genuine DIB, but we caution against an automatic interpretation in terms of an ionic carrier.