The electric field gradient tensor and the tensors of the molecular magnetic susceptibility and the molecular electric quadrupole moment in nitric acid: A high-resolution rotational Zeeman effect study

Abstract High-resolution zero field and Zeeman rotational spectra have been studied for HNO 3 and DNO 3 . The measured values for the 14 N nuclear quadrupole coupling constants are χ + = χ bb + χ cc = −0.929(6) MHz and χ − = χ bb − χ cc = −0.789(10) MHz for HNO 3 and χ + = 0.731(6) MHz and χ − = −0.576(10) MHz for DNO 3 . The measured molecular g values are g aa = −0.1213(3), g bb = −0.1097(2), and g cc = −0.0493(2) for HNO 3 and g aa = −0.1271(1), g bb = −0.0970(1), and g cc = −0.0474(1) for DNO 3 . The two independent components of the magnetic susceptibility anisotropy in units of 10 −6 erg G −2 mole −1 are 2 ξ aa − ξ bb − ξ cc = −0.4(4) and 2 ξ bb − ξ cc − ξ aa = +7.9(4) for HNO 3 and 2 ξ aa − ξ bb − ξ cc = +1.2(3) and 2 ξ bb − ξ cc − ξ aa = +6.2(3) for DNO 3 , where a , b , and c denote the molecular principal inertia axes. From these values and from the known relative position and orientation of the principal inertia axes systems of the two isotopomers, the complete tensors of the molecular magnetic susceptibility, the molecular electric quadrupole moment, and the intramolecular electric field gradient at the 14 N nucleus are calculated. The latter is compared to recent ab initio results. The large discrepancies between the two data sets can be reduced, if the SCF-value for the electronic contribution to the intramolecular electric field gradient is appropriately scaled.