Gate-pulse-induced recombination, known as the charge pumping (CP), is a fundamental carrier recombination process, and has been utilized as a method for analyzing electrical properties of defects (or dangling bonds) at the transistor interfaces, which is now recognized to be well-matured and conventional. Nevertheless, neither the origin (the bonding configuration) of the defects responsible for the CP, nor their detailed recombination sequence has been clarified yet for Si metal-oxidesemiconductor (MOS) interfaces. In order to address these problems, we investigated the CP under spin resonance conditions at temperatures ranging from 27 to 300 K in Si(100) n-type MOS transistors. We obtained evidence that P b0 and E' centers, the two major dangling bonds at (and near) the Si(100) interface, participate in the CP recombination process. We also show that the spin-dependent CP process is explained by the formation of electron-electron spin pairs, which in turn reveals that the CP via P b0 and E' centers is inherently a two-electron process.