Knowledge Bank

Observations of the infrared spectra of $N2-CO$ by diode laser spectroscopy have been reported $previouslyab$. The present study is an observation of the rotational spectra of $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N2-CO,\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N14N-CO$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N2-CO$ using a Fourier transform microwave spectrometer. Two sets for the $J=2-1,3-2$, and 4-3 transitions are observed for $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N2-CO$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N2-CO$, while only one set for $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N14N-CO$. The hyperfine structures are observed for the complexes containing $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N$ nucleus. The first set is assigned to the K=0 state of $ortho-N2$ and the second to the K=1 state of $para-N2$, based on the infrared analysis and eQq splittings. The transitions with the $K=1$ state are stronger than those with the $K=0$ state for $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N2-CO$ complex, while the reversed is observed for $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N2-CO$. In the case of $\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}N14N-CO$ only lowest transition is observed because of lack of symmetry in the complex. The nuclear electric quadrupole coupling constant of the $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N$ nucleus is much smaller than related complexes. The value of the van der Waals stretching frequency for $N2-CO$ is calculated to be $19cm-1$ from the rotational and the centrifugal distortion constants obtained. We concluded that both moieties, $N2$ and CO, are rotating almost freely in the complex $N2-CO$.