Rotational spectrum of cis–cis HOONO

Abstract

The pure rotational spectrum of cis-cis peroxynitrous acid, HOONO, has been observed. Over 220 transitions, sampling states up to JЈϭ67 and K a Јϭ31, have been fitted with an rms uncertainty of 48.4 kHz. The experimentally determined rotational constants agree well with ab initio values for the cis-cis conformer, a five-membered ring formed by intramolecular hydrogen bonding. The small, positive inertial defect ⌬ϭ0.075667(60) amu Å 2 and lack of any observable torsional splittings in the spectrum indicate that cis-cis HOONO exists in a well-defined planar structure at room temperature.

Internal rotation in peroxynitrous acid (ONOOH)

“…We also carry out calculations in parallel on the trans-perp conformer. Like the cis-cis conformer, 25,26,51,63,65,66 the trans-perp conformer 63,64,66,67 has been observed in recent gas-phase experimental studies. To take advantage of the wealth of pertinent gas-phase experimental data available for isomeric nitric acid that can be compared to analogous theoretically-derived results, additional calculations on HONO 2 are presented.…”

“…Although all of the calculated data correspond to equilibrium values, the CCSD͑T͒ rotational constants are within 0.5% and the CCSD͑T͒ dipole magnitude is within 1-3 % of the respective observed values. The rotational constants of the cis-cis and trans-perp conformers have also been determined in recent gas-phase experiments 65,67 and ͑Table V͒ are uniformly within 1% of the CCSD͑T͒ values. Taken together, these comparisons suggest that the CCSD͑T͒/avtz r e and e of Tables III and V can be usefully employed in cases where the analogous experimental data have not been determined.…”

“…This result, which is at variance with most of the other studies listed in Table II, seems to have been accepted in the most recent gas-phase experimental studies. [63][64][65][66][67] Assuming the QCISD͑T͒/cc-pVTZ result is correct, clearly, calculations from higher levels of theory using basis sets including diffuse functions need to be carried out.…”

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

“…Our previous work 15 on the pure rotation spectrum of cis-cis HOONO provided a potential means for specific atmospheric identification from balloon, aircraft, or groundbased millimeter and submillimeter spectrometers. An accurate determination of the permanent electric dipole moment is essential to determine the measurement sensitivity required for atmospheric detection or to quantify HOONO concentrations measured in absorption or emission in the laboratory.…”

“…The submillimeter wave rotational spectroscopy of ciscis HOONO has been expanded from the previous assign- ment of 225 lines in the 179-640 GHz range, fit with a standard deviation of 48.4 kHz, 15 to a current data set of 480 lines ͑115 blended lines of 2, 3, or 4 transitions and 174 nonblended lines͒ in the 13-840 GHz range, fit with a standard deviation of 50.6 kHz. The measured and calculated frequencies and quantum number assignments are found in the JPL millimeter and submillimeter spectral line catalog at http://spec.jpl.nasa.gov/catalog, and the HOONO SPFIT and SPCAT files are included in the supplemental material.…”