Detection of deuterated cyanodiacetylene /DC5N/ in Taurus Molecular Cloud 1

Abstract

The J = 9-8 and J = 10-9 transitions of deuterated cyanodiacetylene (DC5N) have been detected at 22.9 and 25.4 GHz in Taurus Molecular Cloud 1. The abundance ratio DC5N/HC5N is found to lie in the range 0.006-0.016, which overlaps the range 0.013-0.017 observed for DCO(+)/HCO(+), and is less than the range 0.02-0.08 determined for DC3N/HC3N. The observation that R(DC5N) is approximately 0.5 R(DCO(+)), is consistent with a model in which HC5N is formed on grains and subsequently deuterated by reactions with H2D(+) in the gas phase.