Patent ID: 8525106

Claim:
A method of transmitting ions in a mass spectrometer having an ion source with an ion exit and a mass analyzer and maintained in a sub-atmospheric pressure regime, comprising: (a) generating analyte ions in the ion source, the ion source having an ion source volume comprising a plurality of subvolumes; (b) applying extraction voltages for extracting analyte ions through the ion exit, wherein the extraction voltages and geometrical dimensions of the ion exit are configured so that analyte ions generated in substantially all of the subvolumes of the ion source volume are extracted and an energy distribution width of the extracted analyte ions is maximized; (c) transmitting the extracted analyte ions through an ion guide to the mass analyzer, the ion guide being filled with an interaction gas; and (d) configuring at least one of an inner width of the ion guide, operating voltages applied to the ion guide, a length of the ion guide, and a pressure of the interaction gas so that the analyte ion energy distribution width is narrowed and the analyte ions are collimated within the ion guide.