Lecture 11

Lecture 11 - EEE 434/591Quantum Mechanics L11:1 David K....

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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L11:1 EEE 434/591—Quantum Mechanics David K. Ferry Regents’ Professor Arizona State University Approximation (to a group photo)
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EEE 434 Quantum Mechanics http://www.eas.asu.edu/~ferry/EEE434.htm L11:2 In general, there are very few problems which can be solved exactly in quantum mechanics. We have seen some of these: infinite quantum well, barrier reflection and tunneling. We shall see another one, the harmonic oscillator, a little later. In the case of the triangular potential and the finite quantum well, we have to resort to approximations. What we want to discuss this lecture is a more formal approach to such approximations with a general theory that can apply to a wide range of problems. But, what we get are good guesses, not accurate answers.
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http://www.eas.asu.edu/~ferry/EEE434.htm L11:3 Approximation Methods: The WKB Method (Wentzel-Kramers-Brillouin) So far, we have worked with simple potentials However, it was clear from the general case, with different barriers, that the problem can become quite complicated. In general, the tunneling is NOT near the top of the barrier, and the transmission coefficient will be dominated by the exponential behavior: Hence, we would like to find an approximation technique that emphasizes just this point. http://en.wikipedia.org/wiki/WKB_approximation
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This note was uploaded on 10/03/2010 for the course EEE 434 taught by Professor Roedel during the Fall '08 term at ASU.

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Lecture 11 - EEE 434/591Quantum Mechanics L11:1 David K....

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