Knowledge Bank

The rotational spectrum of LiNC has been measured for the first time. We succeeded in producing a supersonic molecular beam (1% LiNC in Ar). The LiNC molecule has been produced in two totally different chemical reactions. Two rotational transitions in the ground vibrational state at 26.6 and 53.2 GHz were observed being $J=1\leftarrow 0$ and $J=2\leftarrow 1$. The hyperfine structure was resolved and identified microwave double resonance. The results for the rotational constants are: $Be=13293.293(3)$ MHz, $De=32.5(4)$ KHz; the quadrupole coupling constants are : eqQ(Li) = 0.366(30) MHz, eqQ(N) = 2.944(10) MHz. The $J=1\leftarrow 0$ rotational transition of $\mathrm{<mrow\; data-mjx-texclass="ORD">6</mrow>}$LiNC at 29.2 GHz was observed in natural abundance, Yielding $B1$ = 14591.504 (20) MHz. From this we can conclude that LiNC has a linear isocyanide structure. In earlier work we observed the rotational spectrum of KCN and NaCN and we found surprisingly a T-shaped structure for both molecules. The results for the effectives structural parameters are: , and . We did not observe transitions of excited vibrational states of LiCN (abundance in the beam $\le 3\%$). This leads to an estimated isomerization energy $\ge 120cm-1$. The agreement between our experimental results and recent ab initio calculations is good.