What do s and t mean in the Heitler-London method?

[LagrangeEuler]

http://books.google.rs/books?id=vrc...epage&q=Nolting Heitler London method&f=false

What means labels $$s$$ and $$t$$ on page 189. formula 5.37
$$|\psi_s\rangle=|q\rangle^{(+)}|0;0\rangle$$
$$|\psi_t\rangle=|q\rangle^{(-)}|1;m_s\rangle$$
?

 

[Bill_K]

s stands for singlet (antisymmetric) and t stands for triplet (symmetric)

 

[LagrangeEuler]

Tnx. One more question. Is it mistake in relations 5.38?

$$(\frac{p_1^2}{2m}-\frac{e^2}{2\pi\epsilon_0r_{1a}})|\psi_a^{(1)} \rangle=E_a|\psi_a^{(1)}\rangle$$

Why not

$$(\frac{p_1^2}{2m}-\frac{e^2}{4\pi\epsilon_0r_{1a}})|\psi_a^{(1)} \rangle=E_a|\psi_a^{(1)}\rangle$$
?