  We report the observation of the self-guided propagation of 120 fs, 0.56 mJ
infrared radiation in air for distances greater than one meter. In contrast to
the known case of filamentation, in the present experiment the laser power is
lower than the collapse threshold. Therefore the counter balance between Kerr
self focussing and ionization induced defocussing as the stabilizing mechanism
is ruled out. Instead, we find evidences of a process in which the transversal
beam distribution reshapes into a form similar to a Townes soliton. We include
numerical support for this conclusion.
