Round 11: Tossup 15

The rate of this process increases in a resonant cavity in the Purcell effect. In three-level systems, a form of this process drops atoms from the metastable energy state E2 to E1. The probabilities of two types of this process are described by the Einstein A21 (15[1])and B21 coefficients. Gain media like rubies facilitate one form of this process, which exceeds the rate of (*) absorption in systems displaying population inversion. This process’s “spontaneous” form occurs naturally (10[1])as an excited atom drops to a lower energy state, but its “stimulated” form occurs in a chain reaction (10[1])in barcode scanners. For 10 points, lasers are named for performing what process of releasing light? ■END■ (10[1])

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