Roman Kochanov

Accurate ab initio dipole moment surfaces of ozone: First principle intensity predictions for rotationally resolved spectra in a large range of overtone and combination bands

Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of 16O3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works. For the first time, a very good agreement of first principle calculations with the experiment was obtained for the line-by-line intensities in rotationally resolved ozone spectra in a large far- and mid-infrared range. This includes high overtone and combination bands up to ΔV = 6. A particular challenge was a correct description of the B-type bands (even ΔV3 values) that represented major difficulties for the previous ab initio investigations and for the empirical spectroscopic models. The major patterns of various B-type bands were correctly described without empirically adjusted dipole moment parameters. For the 10 μm range, which is of key importance for the atmospheric ozone retrievals, our ab initio intensity results are within the experimental error margins. The theoretical values for the strongest lines of the ν3 band lie in general between two successive versions of HITRAN (HIgh-resolution molecular TRANsmission) empirical database that corresponded to most extended available sets of observations. The overall qualitative agreement in a large wavenumber range for rotationally resolved cold and hot ozone bands up to about 6000 cm-1 is achieved here for the first time. These calculations reveal that several weak bands are yet missing from available spectroscopic databases.

First-Principles Computed Rate Constant for the O + O2 Isotopic Exchange Reaction Now Matches Experiment

We show, by performing exact time-independent quantum molecular scattering calculations, that the quality of the ground electronic state global potential energy surface appears to be of utmost importance in accurately obtaining even as strongly averaged quantities as kinetic rate constants. The oxygen isotope exchange reaction, 18O + 32O2, motivated by the understanding of a complex long-standing problem of isotopic ozone anomalies in the stratosphere and laboratory experiments, is explored in this context. The thermal rate constant for this key reaction is now in quantitative agreement with all experimental data available to date. A significant recent progress at the frontier of three research domains, advanced electronic structure calculations, ultrasensitive spectroscopy, and quantum scattering calculations, has therefore permitted a breakthrough in the theoretical modeling of this crucial collision process from first principles.

CAVITY RING-DOWN SPECTROSCOPY OF HYDROGEN IN THE 784-852 NM REGION AND CORRESPONDING LINE SHAPE IMPLEMENTATION INTO HITRAN

YAN TANa, JIN WANG, CUNFENG CHENG, AN-WEN LIU, SHUI-MING HU, Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, China; PIOTR WCISLO, Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland; ROMAN V KOCHANOVb, IOULI E GORDON, LAURENCE S. ROTHMAN, Atomic and Molecular Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.

HITRANonline: A NEW STRUCTURE AND INTERFACE FOR HITRAN LINE LISTS AND CROSS SECTIONS

We present HITRANonline, an online interface to the internationally-recognised HITRAN molecular spectroscopic database[1], and describe the structure of its relational database backend[2]. As the amount and complexity of spectroscopic data on molecules used in atmospheric modelling has increased, the existing 160-character, text-based format has become inadequate for its description. For example, line shapes such as the Hartmann-Tran profile[3] require up to six parameters for their full description (each with uncertainties and references), data is available on line-broadening by species other than “air” and “self” and more than the current maximum of 10 isotopologues of some molecules (for example, CO2) can be important for accurate radiative-transfer modelling. The new relational database structure overcomes all of these limitations as well as allowing for better data provenance through “timestamping” of transitions and a direct link between items of data and their literature sources. To take full advantage of this new database structure, the online interface HITRANonline, available at www.hitran.org, provides a user-friendly way to make queries of HITRAN data with the option of returning it in a customizable format with user-defined fields and precisions. Binary formats such as HDF-5 are also supported. In addition to the data, each query also produces its own bibliography (in HTML and BibTeX formats), “README” documentation and interactive graph for easy visualization.

HITRAN IN THE XXIst CENTURY: BEYOND VOIGT AND BEYOND EARTH

The line-by-line portion of the most recent HITRAN2012 editiona contains spectroscopic parameters for 47 gases and associated isotopologues. Continuing the effort of the last five decades, our task has been to improve the accuracy of the existing parameters as well as to add new bands, molecules, and their isotopologues. In this talk we will briefly summarize some of the most important efforts of the past year. Particular attention will be given to explaining the new development in providing line-shape information in HITRAN. There are two important directions in which the database is evolving with respect to line shapes. The first direction is that, apart from the Voigt profile parameters that were traditionally provided in HITRAN, we are able to add parameters associated with many “mainstream” line shapes, including Galatry, speed-dependent Voigt, and the HT profileb recently recommended by IUPACc. As a test case, we created a first complete dataset of the HT parameters for every line of molecular hydrogen in the HITRAN database. Another important development is that in order to increase the potential of the HITRAN database in planetary sciences, experimental and theoretical line-broadening coefficients, line shifts and temperature-dependence exponents of molecules of planetary interest broadened by H2, He, and CO2 have been assembled from available peer-reviewed sources. The collected data were used to create semi-empirical models for calculating relevant parameters for every line of the studied molecules in HITRAN. This work has been supported by NASA Aura Science Team Grant NNX14AI55G and NASA Planetary Atmospheres Grant NNX13AI59G.