Analyzing 3 Electron States in Different Orbital Levels

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SUMMARY

The discussion centers on analyzing three electrons in distinct orbital levels (n, m, p) and determining the number of possible states. The key equations for constructing symmetric and anti-symmetric wavefunctions are provided, including specific formulations for cyclic permutations. The conclusion reached is that while the symmetric spin part yields four states, the total number of states, considering quantum mechanics, is eight. The distinction between classical and quantum mechanics is emphasized, particularly regarding the indistinguishability of electrons.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly electron indistinguishability.
  • Familiarity with wavefunction construction and symmetry properties.
  • Knowledge of angular momentum in quantum systems.
  • Basic grasp of permutation symmetries in quantum states.
NEXT STEPS
  • Study the implications of electron indistinguishability in quantum mechanics.
  • Learn about angular momentum coupling in quantum systems.
  • Explore the construction of multi-electron wavefunctions in quantum mechanics.
  • Investigate the role of symmetry in quantum state analysis.
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Students and professionals in physics, particularly those focusing on quantum mechanics, wavefunction analysis, and angular momentum in multi-electron systems.

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Homework Statement


Consider three electrons in three different orbital levels n, m and p. We
assume that there is one electron in each orbital level. How many states
are then possible?

Homework Equations


Equations for constructing symmetric and asymmetric wavefunctions:

Symmetric under pair permutation:
$$ \frac{1}{\sqrt{6}} \{\left |nmp\right \rangle + \left |mpn\right \rangle + \left |pnm\right \rangle +\left |npm\right \rangle + \left |pmn\right \rangle + \left |mnp\right \rangle \} $$Anti-symmetric under pair permutation:
$$ \frac{1}{\sqrt{6}}\{\left |nmp\right \rangle + \left |mpn\right \rangle + \left |pnm\right \rangle - \left |npm\right \rangle - \left |pmn\right \rangle - \left |mnp\right \rangle \} $$

Symmetric under cyclic permutation:

$$ \frac{1}{\sqrt{3}} \{ \left |nmp\right \rangle + \varepsilon \left |mpn\right \rangle + \varepsilon^* \left |pnm\right \rangle \}$$
$$ \frac{1}{\sqrt{3}} \{ \left |npm\right \rangle + \varepsilon \left |pmn\right \rangle + \varepsilon^* \left |mnp\right \rangle \}$$

With:

$$ \varepsilon = e^{i\frac{2 \pi}{3}} $$
$$ \varepsilon^* = \varepsilon^2 $$

Anti-symmetric under cyclic permutation:

$$ \frac{1}{\sqrt{3}} \{ \left |npm\right \rangle + \varepsilon^* \left |pmn\right \rangle + \varepsilon \left |mnp\right \rangle \} \}$$
$$ \frac{1}{\sqrt{3}} \{ \left |nmp\right \rangle + \varepsilon^* \left |mpn\right \rangle + \varepsilon \left |pnm\right \rangle \}$$

The Attempt at a Solution


I could get the symmetric spin part of the wave function and use that with the anti-symmetric orbital part:
$$ \left | \uparrow \uparrow \uparrow \right \rangle $$
$$ \frac{1}{\sqrt{3}} \{ \left | \downarrow \uparrow \uparrow \right \rangle + \left | \uparrow \downarrow \uparrow \right \rangle + \left | \uparrow \uparrow \downarrow \right \rangle \}$$
$$ \frac{1}{\sqrt{3}} \{ \left | \uparrow \downarrow \downarrow \right \rangle + \left | \downarrow \uparrow \downarrow \right \rangle + \left | \downarrow \downarrow \uparrow \right \rangle \}$$
$$ \left | \downarrow \downarrow \downarrow \right \rangle $$There should be 8 states, but this only gives me 4. I don't know how to get the asymmetric spin part.
 
Physics news on Phys.org
According to classical mechanics the electrons are distinguishable.

But quantum mechanically you can't distinguish the electron and can't say i-th electron is in j-th state.What can you do? You can just distinguish the angular momentum component along the z direction of the electron system.And so the solution above given is right.As the electron is spin half particle so the given four solutions represents just the 3/2,1/2,-1/2,-3/2 angular momentum states
 

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