# Determine electronic transitions by the emitted wavelength?

by FountainPen
Tags: determine, electronic, emitted, transitions, wavelength
 P: 2 1. The problem statement, all variables and given/known data What is the electronic transition of He II when it emits 468.6 nm photon. 2. Relevant equations $$\frac{1}{\lambda}=4R\left(\frac{1}{m^2}-\frac{1}{n^2}\right)$$ 3. The attempt at a solution I know it is a pashen-alpha line from googling but I don't know how to find that from this equation with two unknowns. I know the energy levels are discrete so there is probably only one transition that makes this wavelength. Don't know why He II and not He I so I might be missing something.
 HW Helper Thanks P: 9,675 HeI is the neutral He atom, HeII is the once-ionized helium, it has a single electron. The energy levels of HeII can be treated with the Bohr model, with Z=2. You can find n and m by trial and error. They must be integer numbers in principle. m is the final state, it can be 1, 2, 3,... Find n for each of them. Because of the uncertainty of the wavelength, it will not be an integer number exactly, but it has to be very close to an integer. ehild
 P: 2 Thanks for explaining what He II is. I thought there would be some sort of mathematical way to determine the transition without brute force. Oh well.

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