This is an introduction to our Visualization of Atomic Collisions Calculations . (It has been written originally in 1995, so the format is not technically perfect.)

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This is a picture describing the basis of the (semi) classical collision theory. On the next picture, the plane is rotated into the screen plane.

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The collision plane, seen on the previous perspective drawing, rotated into the screen plane

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The theory: Time dependent Schroedinger equation relevant for the collision process. The expansion in a basis set is shown. Also shown are the kinetic energy of the electron and the two potentials, describing the interaction with the target and the projectile.

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Using the expansion and evaluating projections on the basis states, one obtains a set of coupled equations for the coefficients as functions of time.

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In most cases, one is satisfied by obtaining the expansion coefficients, since the occupation probabilities (and the experimentally relevant quantities) can be obtained from them. However, there is also the concept of probability density and probability density current. These two quantities are defined above.

To obtain them, we must use the basis states in "all points", i.e. on a certain mesh. This is an additional computational effort, which cannot lead to any comparison with experiment.

It can, however, provide cllues for understanding of the mechanisms.

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This is a plot of probability density. Each new pattern is factor 2 down, i.e. exponential scale with steps of log 2.

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This is the corresponding probability density current.

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Here the two previous are compared.

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Once more the definitions......

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This is a cut from a movie, which one can run in task 5. This particular picture compares two densities toowards the "end" of the collision. The difference is in the starting condition: The upper starts in "3p-" state, the lower in "3p+ state. See on the next picture what does it mean in terms of currents.

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These are the coresponding currents "before" the collision. The picture tells more than words and formulae.

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Now that collision is "finished". Can you describe the difference? Can it be understood (or made probable) using classical arguments?

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Another starting point: the states are prepared in alligned states. What will be the difference now?

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Here and in the following are pictures of densities (and at the end 1 current), constructed from simple amplitudes, equal to 1. These plots show the hydrogenic state densities.

BACK .... TOP .... NEXT Here and in the following are pictures of densities (and at the end 1 current), constructed from simple amplitudes, equal to 1. These plots show the hydrogenic state densities.

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Back to the animations of the Li+ ion collision with Na atom.....
Back to the Atomic Movies demo.....