.

$$\left ( \begin{array}{cccc} \alpha&0 & 0 & -\beta^h\\ 0 &\al... ... & \alpha & 0\\ -\beta^h & 0 & 0 & \alpha \end{array}\right )$$ (17)

The difference between the two reaction paths shows up in the H_1-4 term, where the product of sines reflects the difference in signs between the two angles.