Question 2 b) of the attatched PDF   In a laser cooling experiment, the transition 52S1/2 : F = 2 ...

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Question 2 b) of the attatched PDF   In a laser cooling experiment, the transition 52S1/2 : F = 2   to   52P3/2; F' = 3 is excited by light that has frequency detuning  delta = Gamma / 2. Selection rules dictate that the excited state decays back to the initial state so there is a nearly closed cycle of absorption and spontaneous emission, but there is some off-resonant excitation to the F' = 2 hyperne level which can decay to F = 1 and be 'lost' from the cycle. The F' = 2 level lies about 45Gamma below the F' = 3 level.   Estimate the average number of photons scattered by an atom before it falls into the lower hyperfine level of the ground state conguration. Assume I = ISAT and that the transitions have similar strengths.