GASPHASE ION SOURCE FOR TIME-OF-FLIGHT MASS-SPECTROMETERS WITH HIGH MASS RESOLUTION AND LARGE MASS RANGE

摘要

To achieve a high mass resolution in a time-of-flight mass-spectrometerwith gasphase ion source, the initial velocity components in the direction of acceleration of the ion source must be kept small. This can be done by injecting the analyte gas or ion beam at right angles to the direction of acceleration into the ion source. When the direction of acceleration and the direction of the analyte gas or ion beam or not colinear, the amount of unwanted gas ballast in the drift space of the time-of-flight mass-spectrometer will be less. This will increase the dynamic range of the mass-spectrometer. The heavier an ion is, the more its path will deviate from the axis of the ion source and if it deviates too far from the axis of the ion source it will be lost. This effect gives the limit of the mass range of such an ion source. If the electrical deflection field for these ions is already within the acceleration region of the ion source, its mass range can significantly be enlarged.