Iouli E. Gordon

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.

Direct-potential-fit analysis of new infrared and UV/visible AΣ+1-XΣ+1 emission spectra of AgH and AgD

New high-resolution infrared and UV/visible spectra of (107)AgH, (109)AgH, (107)AgD, and (109)AgD have been recorded with a Fourier transform spectrometer. The new line positions are combined with published microwave and older electronic A (1)Sigma(+)-X (1)Sigma(+) data and used, first in a decoupled analysis of the X state alone, and then in a global multi-isotopologue analysis which yields comprehensive descriptions of both the X (1)Sigma(+) and A (1)Sigma(+) states of all four isotopologues of AgH. While the A state was long believed to be heavily perturbed, it is shown that its irregular spectrum merely reflects an unusual potential function shape. A direct fit of all data to appropriate radial Hamiltonians yields analytic potential-energy functions and Born-Oppenheimer breakdown radial functions for the ground X (1)Sigma(+) and A (1)Sigma(+) states.

Fourier transform infrared emission spectra of MgH and MgD

High resolution Fourier transform infrared emission spectra of MgH and MgD have been recorded. The molecules were generated in an emission source that combines an electrical discharge with a high temperature furnace. Several vibration-rotation bands were observed for all six isotopomers in the X (2)Sigma(+) ground electronic state: v=1-->0 to 4-->3 for (24)MgH, v=1-->0 to 3-->2 for (25)MgH and (26)MgH, v=1-->0 to 5-->4 for (24)MgD, v=1-->0 to 4-->3 for (25)MgD and (26)MgD. The new data were combined with the previous ground state data, obtained from diode laser vibration-rotation measurements and pure rotation spectra, and spectroscopic constants were determined for the v=0 to 4 levels of (24)MgH and the v=0 to 5 levels of (24)MgD. In addition, Dunham constants and Born-Oppenheimer breakdown correction parameters were obtained in a combined fit of the six isotopomers. The equilibrium vibrational constants (omega(e)) for (24)MgH and (24)MgD were found to be 1492.776(7) cm(-1) and 1077.298(5) cm(-1), respectively, while the equilibrium rotational constants (B(e)) are 5.825 523(8) cm(-1) and 3.034 344(4) cm(-1). The associated equilibrium bond distances (r(e)) were determined to be 1.729 721(1) A for (24)MgH and 1.729 157(1) A for (24)MgD.

The vibration-rotation emission spectrum of MgH2

The gaseous MgH2 molecule has been discovered in an electrical discharge inside a high temperature furnace. The vibration–rotation emission spectrum of 24MgH2 was recorded with a Fourier transform spectrometer and the antisymmetric stretching mode (ν3) was detected near 1589 cm−1. In addition, three hot bands involving ν2 and ν3 were found and rotationally analyzed. The MgH2 molecule has a linear structure with an R0 Mg–H bond distance of 1.703 327(3) A.

Infrared emission spectra and equilibrium bond lengths of gaseous ZnH2 and ZnD2

A detailed analysis of the high resolution infrared emission spectra of gaseous ZnH2 and ZnD2 in the 800-2200 cm(-1) spectral range is presented. The nu3 antisymmetric stretching fundamental bands of 64ZnH2, 66ZnH2, 67ZnH2, 68ZnH2, 64ZnD2, 66ZnD2 and 68ZnD2, as well as several hot bands involving nu1, nu2 and nu3 were rotationally analyzed, and spectroscopic constants were obtained. Rotational l-type doubling and l-type resonance, local perturbations, and Fermi resonances were observed in the vibration-rotation bands of both ZnH2 and ZnD2, and equilibrium vibrational frequencies (omega1, omega2 and omega3) were estimated. Using the rotational constants of the 000, 100, 01(1)0 and 001 vibrational levels, the equilibrium rotational constants (B(e)) of 64ZnH2 and 64ZnD2 were determined to be 3.600 269(31) cm(-1) and 1.801 985(25) cm(-1), respectively, and the associated equilibrium bond lengths (r(e)) are 1.524 13(1) angstroms and 1.523 94(1) angstroms, respectively. The difference between the r(e) values of 64ZnH2 and 64ZnD2 is about 0.01%, and is mainly due to the breakdown of the Born-Oppenheimer approximation.

The HITRAN molecular database

This presentation provides an overview of the updates and extensions of the HITRAN molecular spectroscopic absorption database. The new significantly improved parameters for the major atmospheric absorbers (for instance H2O and O2) have been given particular attention. For most of the molecules, spectral parameters have been revised and updated. The new edition also features many new spectral bands and new isotopic species. The cross-section part of the database has also been significantly extended by adding new species as well as more temperature-pressure sets for existing species. In addition, HITRAN now provides the collision-induced absorption parameters, including those relevant to the terrestrial atmosphere: N2–N2, N2–O2, O2–O2. The study of the spectroscopic signatures of planetary atmospheres is a powerful tool for extracting detailed information concerning their constituents and thermodynamic properties. The HITRAN molecular spectroscopic database has traditionally served researchers involved wit...

Intensity anomalies in the rotational and ro-vibrational spectra of diatomic molecules

We study the anomalies in the distributions of intensities of transitions in the purely rotational bands and the rotational branches of the vibrational bands within the unperturbed ground electronic states in spectra of diatomic molecules. While normally these distributions follow smooth patterns, sudden drops in intensity values are often observed. We analyze the origin of these anomalies in HF, DF, and CO and find that they are predominantly associated with specific forms of the dipole-moment functions (DMFs). The rotational transitions at which these anomalies occur and their severity are very sensitive to these forms, which makes them a promising tool for refining the empirical DMFs.

Fourier transform emission spectroscopy of YbO in the near-infrared region☆

The emission spectrum of gas-phase YbO has been investigated using a Fourier transform spectrometer. Chemiluminescence was observed from excited YbO molecules produced in a Broida-type oven by the reaction of ytterbium metal vapor with N2O. A total of eight red-degraded bands in the range 9800–11 300 cm � 1 were recorded at a resolution of 0.04 cm � 1 . Because of the multiple isotopomers present in the spectra, only three bands were rotationally analyzed. Perturbations were identified in two of these bands and all three transitions were found to terminate at the X 1 R þ ground electronic state. The electronic configurations that give rise to

Publisher Correction: O2−O2 and O2−N2 collision-induced absorption mechanisms unravelled

In the version of this Article originally published, Figures 3 and 4 were erroneously swapped, this has been corrected in all versions of the Article.

O-2-O-2 and O-2-N-2 collision-induced absorption mechanisms unravelled

Collision-induced absorption is the phenomenon in which interactions between colliding molecules lead to absorption of light, even for transitions that are forbidden for the isolated molecules. Collision-induced absorption contributes to the atmospheric heat balance and is important for the electronic excitations of O2 that are used for remote sensing. Here, we present a theoretical study of five vibronic transitions in O2−O2 and O2−N2, using analytical models and numerical quantum scattering calculations. We unambiguously identify the underlying absorption mechanism, which is shown to depend explicitly on the collision partner—contrary to textbook knowledge. This explains experimentally observed qualitative differences between O2−O2 and O2−N2 collisions in the overall intensity, line shape and vibrational dependence of the absorption spectrum. It is shown that these results can be used to discriminate between conflicting experimental data and even to identify unphysical results, thus impacting future experimental studies and atmospheric applications.Molecular collisions can lead to the absorption of incident light even for transitions that are spectroscopically forbidden for the isolated molecules. Now the electronic–vibrational transitions of O2 have been theoretically studied and, contrary to textbook knowledge, it is shown that the absorption mechanism and the spectral line shape depend on the collision partner, oxygen or nitrogen.