Abstract: A method and apparatus for analyzing ions by determining times of flight include establishing an encoded sequence for launching packets of ions from a source region toward a detector. The encoded sequence is one in which the high-mass ions of a leading packet will be passed by the low-mass ions of a trailing packet. Thus, a high efficiency time-of-flight mass spectrometer is formed. The ions of each packet are acted upon to bunch the ions of the packet, thereby compensating for initial space and/or velocity distributions of ions in the launching of the packet. The times of arrival of the ions are determined at the detector to obtain a signal of overlapping spectra corresponding to the overlapping launched packets. A correlation between the overlapping spectra and the encoded launch sequence is employed to derive a single non-overlapped spectrum.