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Homework Help: Singlet and triplet states of H2

  1. Nov 21, 2013 #1
    1. The problem statement, all variables and given/known data

    The wave function for a system of two hydrogen atoms can be described approximately in
    terms of hydrogen wave functions.
    (a) Give the complete wave functions for the lowest states of the system for singlet and triplet
    spin configurations. Sketch the spatial part of each wave function along a line through the
    two atoms.
    (b) Sketch the effective potential energy for the atoms in the two cases as functions of the
    internuclear separation. Neglect rotation of the system. Explain the physical origin of the
    main features of the curves, and of any differences between them.

    2. Relevant equations

    The complete wavefunction is ψ(x1,x2)[itex]\chi[/itex](s1,s2) for a two particle system, assuming the spatial wavefunction and the spin are separable.

    Hydrogen ground state is ψ100= [itex]\frac{1}{\sqrt{\pi}}[/itex][itex](\frac{1}{a})^{3/2}[/itex][itex]e^{-\frac{r}{a}}[/itex]

    Singlet (anti-symmetric) state is | 0 0 > = [itex]\frac{1}{\sqrt{2}}[/itex]([itex]\uparrow[/itex][itex]\downarrow[/itex]-[itex]\downarrow[/itex][itex]\uparrow[/itex])
    Triplet (symetric) states are:
    | 1 1 > = [itex]\uparrow[/itex][itex]\uparrow[/itex]
    | 1 0 > = [itex]\frac{1}{\sqrt{2}}[/itex]([itex]\uparrow[/itex][itex]\downarrow[/itex]+[itex]\downarrow[/itex][itex]\uparrow[/itex])
    | 1 -1 > = [itex]\downarrow[/itex][itex]\downarrow[/itex]

    3. The attempt at a solution

    I try to compose the total wavefunction with the spatial part and the spin states, but I am not sure how to deal with the fact that there are two electrons that are under the Coulomb potential of both protons.

    Since there are two electrons in this system both spin-1/2, would the system be viewed as spin-1 and therefore a symmetric total wavefunction?

    I am clueless as to what the question is asking. Maybe with an understanding of part a), it would become clear.

    I would really appreciate it if someone can point me in the right direction. Thanks!
  2. jcsd
  3. Nov 22, 2013 #2


    User Avatar

    Staff: Mentor

    That's not important, as you are only approximating the exact wave function. What is important to keep in mind is that you are combining two wave functions that are centered on different atoms.

    No no no! The Pauli principle applies to many particle wave functions. The wave function must be antisymmetric under the exchange of two identical fermions.
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