The invention relates to a high-pressure gas discharge lamp, particularly a
motorcar lamp, comprising a bulb including at least two neck portions and
a vacuum-tight discharge vessel of quartz glass, at least two electrodes
projecting into the discharge vessel, and a filling in the discharge
vessel which, in the operating state, is in a discharge state. Such lamps
are used, in particular, in headlights of motorcars. In order to ensure
that the arc of the high-pressure gas discharge lamp generates a higher
luminescence in a small area, and the lamp can be used as a light source
in motorcar headlights, the discharge vessel of the high-pressure gas
discharge lamp in accordance with the invention encloses a discharge space
having a width B below 4 mm and a length C below 8 mm, and the filling
comprises NaI, ScI.sub.3, Xe, ZnI.sub.3 and is free of Hg. Surprisingly it
has been found that the use ZnI.sub.2 in the filling causes the arc to
generate a higher luminescence in the area of the arc axis per dimension
of the arc. In the case of motorcar headlights, forming the desired light
beam on the street requires the light source to be as punctiform as
possible, i.e. the highest possible luminescence is generated in a small
area. This enables the design of the reflector to be improved and the arc
to be more accurately projected on the street. This applies also to
headlights comprising an optical projection system instead of a reflector.
