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Numerical solution of the Schrödinger equation

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The effect <strong>of</strong> l > 0: The orbital angular momentum quantum number,<br />

l, gives a term in <strong>the</strong> potential, Eq. (2), which makes <strong>the</strong> wave function<br />

smaller close to <strong>the</strong> core. The wave functions are <strong>the</strong>n less affected by <strong>the</strong><br />

modified potential close to <strong>the</strong> core, and <strong>the</strong>refore become more similar to<br />

<strong>the</strong> hydrogenic wave functions. We <strong>the</strong>refore expect <strong>the</strong> quantum correction<br />

to be smaller for larger l. Fix l = 1 and determine <strong>the</strong> energy eigenvalues for<br />

n = 2, 3, and 4, and estimate <strong>the</strong> value <strong>of</strong> δ p in this model.<br />

For l = 1: energy eigenvalues and <strong>the</strong> quantum defect δ p .<br />

n Energy, Ẽ(n,1) δ p<br />

2<br />

3<br />

4<br />

A More effective use <strong>of</strong> Matlab<br />

(This remark is on <strong>the</strong> last point in Sec. 2.1.)<br />

The plot will appear in a new window. It is now handy to shrink <strong>the</strong> matlab<br />

window such that <strong>the</strong> two or three windows you need will fit toge<strong>the</strong>r on <strong>the</strong><br />

screen without overlapping one ano<strong>the</strong>r. Note also that it is possible to put<br />

both commands you need (calculations and plotting) on a single line.<br />

[x,f]=ode45(’hydrogen’,[0.001 20], [1 -1]); plot(x,f(:,1))<br />

Youcan<strong>the</strong>nuse <strong>the</strong> arrow-upkey to get back <strong>the</strong>command lineused before,<br />

and do both calculations and plotting in one go.<br />

With <strong>the</strong> method described above you need to change <strong>the</strong> energy value<br />

in hydrogen.m for each calculation. Since that needs to be done very many<br />

times it is much more convenient to instead give <strong>the</strong> energy as one <strong>of</strong> <strong>the</strong><br />

initial values (as described above). One can <strong>the</strong>n e.g. write<br />

[x,f]=ode45(’hydrogen’,[0.001 20], [1 -1 -0.22]); plot(x,f(:,1))<br />

where “-0.22” is <strong>the</strong> energy given as an initial value.<br />

5

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