Transmission coefficient (quantum tunnelling)

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SUMMARY

The transmission probability (T) for a quantum tunneling scenario where the incident particle energy (E) equals the barrier energy (U) is not null and is less than 1. To determine T, one must take the limit of T as E approaches U0, utilizing the approximation of sin x by x when x is near 0. It is essential to solve the Schrödinger equation with E set to U0, as the behavior of the wave function differs significantly depending on the value of k in the equation \(\frac{{d}^{2}\psi}{d{x}^{2}} = k\). Directly substituting E = U0 into existing solutions is incorrect due to the distinct cases for positive, negative, and zero values of k.

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  • Understanding of quantum mechanics principles, specifically quantum tunneling.
  • Familiarity with the Schrödinger equation and its applications.
  • Knowledge of transmission and reflection probabilities in quantum physics.
  • Basic calculus, particularly limits and approximations.
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Homework Statement


What is transmission probability (T), when the incident particle energy (E) is equal to the energy of the barrier (U)?

Homework Equations


Equations to transmission and reflection probabilities.
http://i950.photobucket.com/albums/ad348/gs5720/img099.png?t=1278212132
http://i950.photobucket.com/albums/ad348/gs5720/img098.jpg?t=1278212130

The Attempt at a Solution


I know that the probability isn't null and less than 1, but i don't know how to proceed when the energy of E is equal to U.

That is all the information I have, I would appreciate any help.
 
Last edited:
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Try taking the limit of T as E approaches U0. Use the fact that 1-U0/E will approach 0 and approximate sin x by x when x ~ 0.
 
You'll need to solve the Schrödinger equation with E = Uo.

Don't try to find T by putting E = Uo in those two cases. This is because the solution to \frac{{d}^{2}\psi}{d{x}^{2}} = k is different for the three cases where k is positive, negative or zero. You cannot solve the equation for positive k, and then put k=0 in the solution to obtain the solution for k=0.
So you'll have to solve Schrödinger equation again with E = Uo inside the barrier.
 

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