For a one-photon process, Prof. Yang showed that the selection rules are ΔL = +/- 1 and ΔS = 0. In this bonus problem, we're going to look at the transition from a hydrogen atom in its ground electronic configuration (1s¹) to the excited state configuration 4p¹ by consecutive single-photon processes.

You'll probably want to start out by listing all the possible configurations between 1s¹ and 4p¹ (e.g. 2s¹, 2p¹, etc.) and finding term symbols for each of those states (remember that p¹ defines the term symbol, so 2p¹ has the same term symbol as 3p¹, and so forth). You may want to lay them out in a table: figure 8.4 (p. 307) and figure 8.5 (p. 308) might give you some ideas.

So the question for you to answer is: if you have 1 photon, how many paths get you from 1s¹ to 4p¹? How many paths are there with 2 photons? What about 4 photons? 5? The real show-offs should try 3 photons.