A new technique is developed for measuring the incoherent resonance decay (IRD) and the coherent optical ringing of selectively (±3 MHz) prepared electronic states in solids and gases. The method utilizes electro-optic switching of a single laser mode that is on or off resonance with respect to the homogeneous molecular packets in the excited ensemble. The technique was applied to a variety of systems to give information about their phase memory (optical T 2 processes), radiative and radiationless decay (optical T 1 processes), and to measure directly their optical transition moment between the ground state and the prepared electronic state.