Parts of the 3 mm line survey of IRC +10216 showing the three lines tentatively assigned to the J = 15−14, J = 16−15, and J = 18−17 rotational lines of NCCP. The J = 16−15 line is marginally detected. The rms noise levels per 1 MHz channel are 0.4, 1.2, and 0.8 mK in the bottom, middle, and top panels, respectively. Line profiles calculated under LTE, assuming that NCCP extends between 5 and 20′′ with a homogeneous fractional abundance and rotational temperature of 20 K are shown as thick gray lines.