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Homework Help: Ionization Energy (Quantum Mechanics)

  1. Sep 24, 2012 #1
    1. The problem statement, all variables and given/known data

    When ultraviolet radiation of wavelength 58.4 nm from a helium lamp is directed on to a sample of krypton, electrons are ejected with a speed of 1.59 Mm/s. Calculate the ionization energy of Krypton.

    2. Relevant equations

    E=hv, [itex]\frac{1}{λ}[/itex]=R(1- [itex]\frac{1}{n2}[/itex] ) <- Lyman series
    Ionization energy = [itex]\frac{hcR}{n2}[/itex]

    3. The attempt at a solution

    I used the Lyman series to try and find the Rydberg constant for Krypton (with n=4), then substituted that value into the Ionization energy equation with n = 4 again. I'm given that the answer should be 14 eV, but I didn't get that result.

    My confusion is how these equations relate to the ionization of krypton since the equations assume a single electron atom, which krypton is not. Furthermore, I can't find a use for the velocity (E= 0.5mv2 also doesn't give the correct answer).

    Any help in figuring out how to approach this problem would be greatly appreciated.
  2. jcsd
  3. Sep 24, 2012 #2
    Why do you care about the structure of krypton's spectrum? You have the energy of incident photons, you have the energy of emitted electrons. Where is the difference at?
  4. Sep 24, 2012 #3


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    The Lyman type of series only applies to one-electron atoms or ions. Try relating this problem to the photoelectric effect.
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