1 Introduction

Stark broadening of spectral lines is important for the modellisation of the atmospheres of hot early-type stars, where these lines are strong and can have extended collisional wings due to interactions with electrons, protons and also ionised helium. In spite of numerous efforts oriented towards the obtention of atomic parameters entering the calculation of spectral lines intensities and profiles, a number of such important parameters are still missing. For helium lines, the atomic parameters which are available are numerous (cf. for instance Dimitrijevic & Sahal-Bréchot 1984), but they do not concern lines arising from highly excited levels. In particular, there are six infrared helium lines which perturb the wings of Paschen hydrogen lines observed in hot early-type stars. These hydrogen lines are an efficient tool for determining stellar atmospheres parameters (Jaschek et al. 1994; Frémat et al. 1996). Thus the line profiles of the perturbing helium lines must be known with a sufficient precision for an accurate modellisation of these stellar atmospheres. In the present paper, we present results for Stark widths and shifts for these six infrared lines of helium that have never been calculated before. We have used the impact and quasistatic approximations, and the semi-classical perturbation theory that we have shown to be sufficient for these lines connecting a high and a low level. We have also shown that the isolated line approximation can be used in spite of the high levels involved.