Knowledge Bank

Cavity Fourier-Transform microwave spectroscopy has been used to characterise a gas phase, polar dimer of N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O. The polar (N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ unit is generated by co-expansion of a gas sample containing a small percentage of N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O in a helium backing gas. Transitions in the pure rotational spectra of ($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$, ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$NO)($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O), ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O) and ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ are reported. The measured transitions of ($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ and ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$NO)($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O) are assigned and fitted to Hamiltonians allowing rotational, centrifugal distortion and $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N nuclear quadrupole coupling constants to be determined. Hyperfine structure is assigned for a single $JK-1\prime K+1\prime \prime$$\to$$JK-1\prime \prime K+1\prime \prime \prime \prime$ transition of both isotopomers of ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)($\mathrm{<mrow\; data-mjx-texclass="ORD">15</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O). Nuclear quadrupole coupling constants,$\chi bb$, are reported for all four $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N nuclei. The measured $\chi bb$ are in excellent agreement with those structures predicted from the measured rotational constants. The geometry of the molecule is slipped-parallel. The separation between the central nitrogen nuclei of the monomers in the r structure is 3.570(12){\AA} with the two N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O monomers respectively oriented 54.69(68) and 49.85(64) to the $a$-inertial axis. Simulation of hyperfine structure in the spectrum of the ($\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ isotopomer yields good qualitative agreement with experiment.