In previous studies by the authors, optical emission spectroscopy (OES) was used as a non-intrusive technique for estimating the electron temperature, T-e, of discharges operated for ion plating. This paper reports on further work to investigate the previously observed increase in T-e during the evaporation of titanium. Spatially resolved OES has been used to estimate T-c in the plasma region both before and during evaporation (i) for 1, 2 and 4 Pa argon pressures at a fixed distance from the source, and (ii) for various distances from the source at I Pa argon pressure. The data indicate an increase in T-e during evaporation that decreases for (i) increasing gas pressure and (ii), increasing distance from the source. The results are discussed in relation to the possible contributions from gas rarefaction above the vapour source, Penning ionisation, and vapour-wall interactions. (C) 2003 Elsevier Science B.V. All rights reserved.