Knowledge Bank

The $101-000$ rotational transition of the $C2D3$ radical in the ground electronic state has been detected for Fourier transform millimeter-wave (FTMW) spectrometer. The $C2D3$ produced by discharging the $C2D3Br$ gas diluted in Ar. Thirty-two fine and hyperfine components of the $101-000$ transition are observed in the frequency region around 44.4 GHz. We determined the rotational constant, the spin-rotation interaction constant, and the hyperfine interaction constants accurately for the s and a states caused by the tunneling motion in the $CCD\alpha$ rocking mode. From the nuclear quadrupole interaction constant $\chi aa$ of the $\alpha$ deuteron determined in the present study, the angle between the $C-D\alpha$ bond and the a-axis is estimated to be $148.5\circ$. Furthermore, the lower limit of the energy difference between the s and a states is estimated to be $0.01cm-1$ on the basis of the hyperfine interaction, indicating that the tunneling motion is significant even for $C2D3$.