2py, 2pz orbits
2px-2px bond
F2 molecule. Intensity is proportional to ∫ |Ψ(r)|2dz.
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F2 molecule structure

Isolated F atom has 7 electrons in 4 orbitals
    2s ↑↓     2px ↑     2py ↑↓     2pz ↑↓
2px electrons make 2px-2px σ-bond in F2 molecule. Hydrogen orbitals 2px, 2py are also used to hold non-bonding (lone pair) electrons (note that only 2p electrons are shown).

2px-2px σ-bond

For 2px-2px σ-bond is used orbital
    (1/3)1/2[Ψ2px (r - d) - Ψ2px (r + d)],
where d = (3, 0, 0).

Comments

For atom's orbitals it is nanural to set integration origin at the atom center. Then we break square of the 2px-2px bond in three parts
    [Ψ2px (r - d) - Ψ2px (r + d)]2 =
    Ψ2px (r - d) Ψ2px (r - d) - 2 Ψ2px (r - d) Ψ2px (r + d) + Ψ2px (r + d) Ψ2px (r + d)
and set origin at d, 0, -d correspondingly.
Valence bond theory     updated 4 May 2012