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Quantum Tunneling

  1. Apr 28, 2009 #1
    1. The problem statement, all variables and given/known data
    A 10eV electron is incident on a potential barrier of height 25eV and width 1nm. Estimate (order of magnitude) the probability that the electron will tunnel through the barrier, repeat your calculations for a barrier of 01.nm

    2. Relevant equations
    T=16(E/V)(1-(E/V))exp(-2[tex]\alpha[/tex]a)
    [tex]\alpha[/tex]=[tex]\sqrt{}(2m(V-E))[/tex]/[tex]\hbar[/tex]


    3. The attempt at a solution
    E=10eV=1.6x10^-18J, V=25eV=4x10^-18J

    [tex]\alpha[/tex]=[tex]\sqrt{}(2*9.1x10^-31(4x10^-18-1.6x10^-18))[/tex]/6.62x10^-34=3.157x10^9

    T=3.84exp(-2*3.157x10^9*1x10^-9)=7x10^-3???

    the answer is meant to be 9.2x10^-9 or 4.95x10^-13???? sorry, my book says 4.95 and the lecturers notes say 9.2... doesnt matter, coz im way way off...

    please can someone help me where i am going wrong?
     
  2. jcsd
  3. Apr 28, 2009 #2
    sorry about the latex the x is multiply
     
  4. Apr 28, 2009 #3
    plz anyone?
     
  5. Apr 28, 2009 #4

    Matterwave

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    Gold Member

    Well, the only thing I see is that instead of hbar you used h in your calculations. hbar is a factor of 2pi smaller than h.
     
  6. Apr 28, 2009 #5
    omg oops, thanks
     
  7. Apr 29, 2009 #6
    still have wrong answer, anyone know y?
     
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