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Title: GR9677.099
Post by: conantee on December 08, 2010, 04:54:43 AM
99. The electronic energy levels of atoms of a certain gas are given by E_n = E_1 n^2, where n =1,2,3,.... Assume that transitions are allowed between all levels. If one wanted to construct a laser from this gas by pumping the n=1 \to n=3 transitions, which energy level or levels would have to be metastable?
(A) n=1 only
(B) n=2 only
(C) n=1 and n=3 only
(D) n=1, n=2, and n=3
(E) None