Ethylene in IRC +10216

Ethylene has been detected in the circumstellar gas surrounding the supergiant star IRC +10216. Two lines of the nu sub 7 vibration-rotation band near 28 THz (949/cm) have been seen in absorption at an expansion velocity of 14 km/sec relative to the central star. The line intensities indicate a rotational temperature of T greater than 400 K and a radial C2H4 column density of 10 to the 16th to 10 to the 17th per sq cm.