Dense cores in dark clouds. XI. A survey for N2H+, C3H2, and CCS

We have used the 3 mm receiver and upgraded antenna of Haystack Observatory to make high spatial and spectral resolution observations of lines of N2H and C3H2 in 60 dense cores. Both species are detected in most of the cores , and the velocities, and line widths are well correlated. This suggests th at ions and neutrals are well coupled. We found v(D,max) less than or equal to 0.03 km s(-1), which is the first observational constraint on the relat ive speed of ions and neutrals in star-forming dense cores. Twenty of the c ores were also observed in the J(N) = 4(3)-3(2) line of CCS. From our N2Hobservations, the fractional abundance of the molecular nitrogen N-2 is fou nd to be similar or equal to 7 x 10(-5), consistent with all the nitrogen b eing in molecular form and not depleted onto dust grains.