MICROWAVE SPECTRUM, STRUCTURE AND $l$-TYPE DOUBLING OF DCNO: DEUTERO-FULMINIC ACID

The microwave spectrum of the deuterated form of fulminic acid has been investigated in the frequency region from 10 to 45 GHz. For the ground vibrational state of DCNO the following rotational constants were obtained: $B_{o}(D^{12}C^{14}N^{16}O) = 10 292.51$ MHz, $B_{o}(D^{18}C^{14}N^{16}O) = 10 011.69$ MHz, $B_{o}(D^{12}C^{14}N^{18}O) = 9 759.87$ MHz. These constants yield a combined $r_{***}$ and $r_{o}$-structure: $r(C-D) = 1.027 \\pm 0.001 {\\AA}, r(C-N) = 1.175 \\pm 0.015 {\\AA}$, and $r(N-O) = 1.186 \\pm 0.015 {\\AA}$. The large uncertainties in two of the distances are due to the close proximity of the nitrogen atom to the center of gravity, as it has been observed before in the case of HCNO (refs. $^{1,2}$). For the two degenerate bending modes v*** and v*** the l-type doublets of the transition $J = 1 \\rightarrow 2$ and the two corresponding series of l-type doubling transitions have been observed. The doubling constants are: $q_{4} = 17.92 \\pm 0.05$ MHz, and $q_{5} = 38.09 \\pm 0.05$ MHz. A third series of l-type doubling transitions has been found, whose doubling constant can be expressed as a linear combination of $q_{4}$ and $q_{5}$. For both HCNO and DCNO, rotational transitions $(J = 0\\rightarrow 1 and J = 1\\rightarrow 2)$ of molecules in the following seven vibrational states are now assigned: $(00100), (0001^{1}0), (0002^{0}0), (00001^{1}), (00002^{0}), (000(11)^{\\circ}) \\Sigma^{+}$, and $(000(11)^{\\circ}) \\Sigma^{-}$. In HCNO, the difference between $\\nu_{4}$ and $\\nu_{5}$ was determined to be $200 \\pm 10 cm^{-1}$ from the relative intensities of the $(0001^{1}1^{1})$ and $(00002^{\\circ})$ vibrational satellites.