Laboratory and space spectroscopy of DCO+

Abstract

The rotational spectra of DCO+ and its two isotopomers D{13}^CO+ and DC{18}^O+, produced in a negative glow discharge cell, have been recorded in the 137-792 GHz region, which includes lines from J=2-1 up to J=11-10. The determined rotational and centrifugal distortion constants allow to predict the DCO+ rotational spectrum up to 1000 GHz with an accuracy of 1 part in 10^8 or better. This is important for kinematic studies of dense molecular cloud cores and for future far-infrared observations. We also report on the first detection of the hyperfine structure of the DCO+(1-0) line made at the IRAM 30m antenna, toward the quiescent starless cloud core L1512, in the Taurus Molecular Cloud. We point out that this is the first observation of the hyperfine splitting due to the deuteron. This allowed us to quantify the effects of the hyperfine splitting on the line width determination; if the hyperfine structure is not taken into account in the line fit, the DCO+(1-0) line width is overestimated by a significant factor (> 2).