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The observation of a transient population inversion in the resonance line of strontium is reported. Basically the process involves a two-photon excitation of the upper state in a three-level system, including the resonant level as the intermediate one. Both transitions involved emit superfluorescent pulses revealing the achievement of population inversions. Characteristics of the process are investigated in time and frequency domains.
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Bréchignac et al. (1981) studied this question.
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