The drift velocities of ions in sulphur hexafluoride

The drift velocities of positive and negative ions of sulphur hexafluoride in their parent gas have been measured in a time-of-flight drift tube over a wide range of electric fields E and gas pressures p ( E/p <or=80 v cm -1 torr -1 ) at room temperature. Three species of negative ions and one species of positive ions were observed. The zero-field mobilities of the ions were found to be 0·56(4), 0·47(8), 0·54(5) and 0·59(0) cm 2 v -1 s -1 .