Apparatus and methods are provided for 
trapping, manipulation and transferring ions along RF and 
DC potential surfaces and through RF 
ion guides. Potential wells are formed near RF-field generating surfaces due to the overlap of the radio-frequency (RF) fields and electrostatic fields created by static potentials applied to surrounding electrodes. Ions can be constrained and accumulated over time in such wells. During confinement, ions may be subjected to various processes, such as accumulation, fragmentation, collisional cooling, focusing, 
mass-to-charge filtering, spatial separation 
ion mobility and chemical interactions, leading to 
improved performance in subsequent 
processing and analysis steps, such as 
mass analysis. Alternatively, the motion of ions may be better manipulated during confinement to improve the efficiency of their transport to specific locations, such as an entrance aperture into vacuum from 
atmospheric pressure or into a subsequent vacuum stage.