ABSORPTION-MEASUREMENTS ON A LOW-PRESSURE, INDUCTIVELY-COUPLED, ARGON-MERCURY DISCHARGE FOR LIGHTING PURPOSES .1. THE GAS TEMPERATURE AND ARGON METASTABLE STATES DENSITY

The gas temperature and the absolute density of the argon 4s(3)P(2) le vel in an 80 W inductively coupled low-pressure argon-mercury plasma a re determined for three different argon filling pressures. This is don e by measuring the line profile of the 4s(3)P(2) --> 4p(3)D(3) transit ion in argon, using a tuneable laser diode. Since the width of this ar gon line is found to depend on the kinetic heavy particle temperature only, radial profiles of the gas temperature can be obtained. It turns out that the maximum gas temperature in this discharge (550-810 K dep ending on the filling pressure) is significantly higher than that in a common tubular fluorescent lamp. From the radial distribution of the argon 4s density it can be concluded that the maxima of the electron d ensity and of the electron temperature are situated close to the coil. it is also found that the position of these maxima depends on the arg on filling pressure.