MEASUREMENTS ON THE MOBILITY OF IONS AND IONIC CLUSTERS IN GASES USING (24M)NA+ AS 20 MSEC TRACER

Mobilities of sodium ions and their clusters in gases have been measur ed by gamma-ray spectrometry using the 20 ms isomeric state of Na-24 a s tracer. This isomer is obtained through the decay of Ne-24 which was produced by bombarding Ne-22 with a 7 MeV triton beam. This new techn ique of measurement allows to determine the mobility of sodium ions in non-reacting gases of a pressure higher than 1 mbar. The measured mob ility of Na-24+ was determined to be 3.2 cm2/Vs in pure neon gas at 10 00 mbar. Measurements of the mobility of sodium ions in a diffusion cl oud chamber showed a rapid decrease in the mobility in the region of s upersaturation due to the growth of large clusters. The usable pressur e range from 1 mbar to high pressures in the range of some hundred bar s is interesting because most other methods for cluster studies don't work at such high pressures. This method enables us to measure the mob ility change towards the condensation point and eventually towards the critical point.