[单选题]
According to the selection rule, when a urzmfs ,x72*rphoton 5: takvgtpx*j8/f-t k is emitted or absorbed, transitions can only occur between state with values of-/*vg:jtk xtt8f pak5 l that differ by
A. four units.
B. three units.
C. two units.
D. one unit.
Post time 2024-1-22 00:52:27