Discrete fluorescent saturation regimes in multilevel systems

Abstract

An examination of the fluorescent process in simple and detailed models of multilevel atoms, expressed in terms of the parameter Pij/Cij where Pij and Cij are, respectively, the photoexcitation rate and the collisional excitation rate in the pumped resonance transition i-j, shows that three distinct regimes exist over the full range of this parameter which may be usefully exploited. The regimes are defined by I, Pij/Cij1; II, Pij/Cij1, PijCki; III, Pij/Cij1, PijCki, where Cki is the collisional rate populating the source level i. Regime I is characterized by sensitivity of fluorescent-fluorescent line intensity ratios to the photoexcitation rate Pij. Regime II is characterized, on the other hand, by insensitivity of these line ratios to Pij. If regime III is reached, even fluorescent-nonfluorescent line ratios become independent of Pij. A concrete application of the analysis has been made to the resonant photoexcitation of a carbonlike ion. © 1988 The American Physical Society.