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The purpose of studying excited level lifetimes is to determine the absolute radiative transition probabilities (or oscillator strengths) needed for quantitative spectroscopy and tests of fundamental quantum mechanical principles. The transition probability translates the intensity of an atomic or molecular absorption or emission line into the population of a particular species in the initial level of the transition. From the relative abundances of the various elements, compounds, and ionization stages, much information about the chemistry and dynamics of the source can be inferred. Many other techniques are used to measure radiative lifetimes or oscillator strengths (gf values) besides those discussed in this chapter. One that deserves special mention, because of its potential precision, accuracy, and broad applicability, is the measurement of relative gf values through absorption spectroscopy. |
