Patent ID: 7041967

Claim:
A method of analyzing ions to enhance the separation of groups of ions with different charge states, the method comprising: (1) providing a stream of ions, wherein the stream of ions includes at least a first group of ions having a first charge state and a second group of ions having a second charge state and injecting at least a portion of the stream of ions into an ion processing section for an injection period; (2) trapping at least some of the injected ions in the ion processing section in an axial direction of the ion processing section; (3) thermalizing the trapped ions; and (4) providing, in the ion processing section, an energy barrier having a barrier magnitude that is constant for at least a separation time period, wherein, during the separation time period: (a) the energy barrier has a first effective barrier height with respect to ions in the first group, wherein the first effective barrier height is equal to the first charge state multiplied by the barrier magnitude, and wherein the first effective barrier height is less than the kinetic energy of the first group of ions; and (b) the energy barrier has a second effective barrier height with respect to ions in the second group, wherein the second effective barrier height is equal to the second charge state multiplied by the barrier magnitude, and wherein the second effective barrier height is greater than the kinetic energy of the second group of ions, thereby allowing ions in the first group to preferentially escape from the ion processing section.