Laboratory microwave spectroscopy of the doubly deuterated cyanomethyl radical, D2CCN.

The microwave spectrum of the doubly deuterated cyanomethyl radical (D2CCN) in its ground electronic state (2 B 1) has been observed for the lowest four rotational transitions (NKa,Kc = 10,1-00,0, 20,2-10,1, 21,2-10,1 and 21,1-11,0) using a Fourier transform microwave spectrometer in combination with a pulsed discharge nozzle. A total of 394 hyperfine components were measured and subjected to a least squares analysis which allowed determining twelve hyperfine constants for nitrogen and deuterium nuclei. With this new set of molecular constants we obtained accurate predictions for low N rotational transitions with hyperfine structure, and searched for this species in TMC-1.