1 Introduction

IC 1396 is an extended H II region located in the Cep OB2 association (at a distance of 750 pc) and excited by the O6 star HD 206267. Inside the ionised region, several globules have been identified, characterised by their optically visible bright rim tracing the ionisation front in the direction of the O6 star (Osterbrock 1957). Such globules have long been suspected to be sites of star formation induced by the compression due to the ionisation shock front. The association of some of these globules with IRAS sources has given further support to this hypothesis (Sugitani et al. 1991). IC 1396-N, located at about 11 pc of projected distance from HD 206267, is associated with the brightest of these IRAS sources (21391+5802, $L_{\rm bol} \sim 300~L_{\odot}$, e.g. Wilking et al. 1993) showing a very cold far infrared spectrum and a large circumstellar mass (Wilking et al. 1993; Sugitani et al. 2000), indicating that it should be in an early stage of evolution. Furthermore this source drives an energetic outflow having a dynamical time <10⁵ yr (Sugitani et al. 1989; Codella et al. 2001). These findings represent strong evidence for an on-going star formation activity triggered by radiation-driven implosion, although evidences for a spontaneous onset of the collapse are also provided (Serabyn et al. 1993).

IC 1396-N has been recently also observed with the ISO spectrometers. The far-infrared spectrum from the environments of the IRAS source is extremely rich of molecular emission excited at a temperature in excess of 1500 K (Saraceno et al. 1996) in a dense shock originated along the protostellar outflow. Such a high temperature is expected to give rise also to copious emission from the rotovibrational transitions of H₂ and in particular from the 1-0 S(1) line at 2.12 $\mu$m. In this paper we report the results of narrow band imaging in this line covering all the IC 1396-N globule. These observations provide a powerful tool both to study the morphology of the shocked gas and to indirectly reveal the presence of young embedded sources inside the globule. The narrow band images are also complemented with J, H and K photometry of the region, allowing to study the young star population and test the hypothesis of the triggered star formation.