content_image/302054.jpg content_image/302053.jpg content_image/302052.jpg
ions. The eigen vectors are 

<img src='content_image/302054.jpg'>

where A$_{m}$$_{1(2)}$$_{±}$ are normalization constants, − → r lm = − → r l − − → r $_{m}$, and 

Note that ψ$_{pl}$ = ψ$_{px}$ for l = 3 , 4 and ψ$_{pl}$ = ψ$_{py}$ for l = 5 , 6. The eigen vectors of ε$_{p}$ do not concern us because they are non-bonding states. If there is no bond-bending, then there are only π -bonding for xy-orbitals. It turns out that the eigen vectors have very similar forms as those in eqs. (9). They are shown in Appendix. 

## 0.0.4 4. Spin-orbit interaction and polarization 

We now introduce the spin-orbit interaction in eq. (4). Its effect can be ex- pressed in the following relations 

<img src='content_image/302053.jpg'>

<img src='content_image/302052.jpg'>

