Collision strengths for the optically allowed transitions 1–13 and 2–7, optically forbidden transition 1–4, and the intercombination transition 1–11: solid curve – our DARC calculation, open red square – DW calculations from Landi & Bhatia (2008), solid blue circle – calculations from Zhang & Sampson (1992). The insets show the details of the collision strengths near the background.