Microcalorimetry of dust particles in a radio-frequency plasma

The internal temperature of rhodamine B-dyed dust particles (2rp=1.2 μm) immersed in radio-frequency (rf) plasmas has been measured for various plasma conditions. For this purpose, the dye has been excited with an argon-ion laser and the fluorescent emission of the particles has been recorded with an optical multichannel analyzer system. The temperature has been determined after comparison with calibration curves. In argon, the particle temperature increases with rf power and is independent of pressure. In oxygen, an increase with rf power is observed, too. However, the energy flux towards the particles includes also heating by atom recombination (association) and exothermic combustion reactions. These temperature measurements have been compared with calculations based on the thermal balance, where measurements of gas temperature, electron density, and electron temperature have been used. A good agreement between theory and experiment has been found.