The invention generally relates to two-dimensional mass spectrometry using ion micropacket detection. In certain aspects, the invention provides systems including a mass spectrometer having an ion trap and one or more detectors. The system includes a central processing unit (CPU), and storage coupled to the CPU for storing instructions that when executed by the CPU cause the system to: apply one or more scan functions to the ion trap that excite a precursor ion and eject a product ion from the ion trap; and determine a secular frequency of the product ion by detecting micropackets of the product ion as the micropackets are ejected from the ion trap.