Forbidden Transitions in the C i Sequence

Transition probabilities for most of the astronomically significant members of the C I sequence for the transitions within the ground configuration are presented. For 02+ the total intensity of all transitions, the intensity of 1D2 3p2 (X5007.57), and the ratio of intensities iS0 H `D2: `D2 H 3p2 are tabulated as a function of N and T . For determinations of T in planetary nebulae, differences between present calculations and those made with former transition probabilities become noticeable for N > 10 . For a given value of the observed intensity ratio, the deduced T will now be smaller. It is abown that the low-density approximation for [0 liii I(4363.20)/I(5007.57) is valid only for N < 10 A coronal line observed at 1668.5 A is tentatively assigned to a [P xJ transition.