Systems and methods of generating ions at atmospheric pressure are
presented. These systems and methods include spatially dependent analysis
of a sample using an effusive ionization source. Systems and methods of
isolating samples at atmospheric pressure are presented. These systems
and methods include using a barrier to prevent metastables or electrons
from an effusive ion source from reaching a sample unless the sample is
in an analysis position. Systems and methods of using metastables in
collisionally induced dissociation are presented.