Rotational spectroscopy and dipole moment of cis-cis HOONO and DOONO

Abstract

The rotational spectrum of cis-cis HOONO has been studied over a broad range of frequencies, 13-840 GHz, using pulsed beam Fourier-transform microwave spectroscopy and room-temperature flow cell submillimeter spectroscopy. The rotational spectrum of the deuterated isotopomer, cis-cis DOONO, has been studied over a subset of this range, 84-640 GHz. Improved spectroscopic constants have been determined for HOONO, and the DOONO spectrum is analyzed for the first time. Weak-field Stark effect measurements in the region of 84-110 GHz have been employed to determine the molecular dipole moments of cis-cis HOONO [μa =0.542 (8) D, μb =0.918 (15) D,μ=1.07 (2) D] and DOONO [μa =0.517 (9) D, μb =0.930 (15) D,μ=1.06 (2) D]. The quadrupole coupling tensor in the principal inertial axis system for the N14 nucleus has been determined to be Χaa =1.4907 (25) MHz, Χbb =-4.5990 (59) MHz, Χab =3.17 (147) MHz, and Χcc =3.1082 (59) MHz. Coordinates of the H atom in the center-of-mass frame have been determined with use of the Kraitchman equations, ∫ aH ∫ =0.516 Å and ∫ bH ∫ =1.171 Å. The inertial defects of HOONO and DOONO are consistent with a planar equilibrium structure with significant out-of-plane H atom torsional motion. Comparisons of the present results are made to ab initio calculations. © 2006 American Institute of Physics.