Red lines and crosses present (n,k) values from measurements at IR wavelengths22 and the red dot the measured nVIS value for the C4H2 liquid21. Our estimate based on the gas phase cross section is shown by the gray line. The dashed line presents the results when the kUV is fitted with a set of Gaussian curves and the solid black line presents the case of a 2,000 cm−1 blue-shift on kUV. The shaded cyan area presents the wavelength range sensitive to haze retrieval from the New Horizons observations14. The average k value within this range (see inset) varies between 4.0 × 10−3 and 6.8 × 10−3 for the solid and dashed line cases, respectively. The corresponding value in this range for tholin-type composition is ~0.2 (dash-triple-dotted line).