Rotational Spectrum of the Most Abundant Isotopomers of the Van der Waals Dimer N$\text{}_{2}$···HBr

The rotational spectrum of the two most abundant isotopomers of the weakly bound dimer between dinitrogen and hydrogen bromide, $\text{}^{14}$N$\text{}_{2}$···H$\text{}^{79}$Br and $\text{}^{14}$N$\text{}_{2}$···H$\text{}^{81}$Br, has been measured for the first time. The three lowest J transitions, at frequencies from 2 to 8 GHz, have been studied at conditions of supersonic expansion. The complicated hyperfine splitting structure arising from the three non-equivalent quadrupolar nuclei has been assigned and fitted. The resulting spectroscopic constants and the derived molecular quantities are compared with those for other isotopomers, as well as with experimental and calculated results for other linear dimers involving dinitrogen. A revised value for the nuclear quadrupole splitting constant for free nitrogen molecule,ρ(N)=-5.3(1) MHz, is also derived.