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Determine electronic transitions by the emitted wavelength? 
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#1
Sep111, 08:42 PM

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 [tex]\frac{1}{\lambda}=4R\left(\frac{1}{m^2}\frac{1}{n^2}\right)[/tex] 3. The attempt at a solution I know it is a pashenalpha 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. 


#2
Sep111, 11:55 PM

HW Helper
Thanks
P: 10,767

HeI is the neutral He atom, HeII is the onceionized 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 


#3
Sep111, 11:59 PM

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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