This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.

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The HITRAN 2008 molecular spectroscopic database

The Cologne Database for Molecular Spectroscopy, CDMS: a useful tool for astronomers and spectroscopists

A new, noniterative triples correction to the coupled‐cluster singles and doubles (CCSD), method, for general single determinant reference functions is proposed and investigated numerically for various cases, including non‐Hartree–Fock (non‐HF) reference functions. It is correct through fourth‐order of perturbation theory for non‐HF references, and unlike other such methods, retains the usual invariance properties common to CC methods, while requiring only a single N7 step. In the canonical Hartree–Fock case, the method is equivalent to the usual CCSD(T) method, but now permits the use of restricted open‐shell Hartree‐Fock (ROHF) and quasirestricted Hartree–Fock (QRHF) reference determinants, along with many others. Comparisons with full configuration interaction (FCI) results are presented for CH2, CH2+, CH3, NH2, and SiH2. The paper also reports the derivation and initial computational implementation of analytical gradients for the ROHF‐CCSD(T) method, which includes unrestricted Hartree–Fock (UHF) CCSD...

Coupled‐cluster methods with noniterative triple excitations for restricted open‐shell Hartree–Fock and other general single determinant reference functions. Energies and analytical gradients

This paper describes the implementation of a fully automated code for the building of anharmonic force constants and their use in a second-order perturbative evaluation of vibrorotational parameters. Next, a number of test applications are discussed, which show the strengths and limits of various computational levels.

Anharmonic vibrational properties by a fully automated second-order perturbative approach

The development of wave optics for light brought many new insights into our understanding of physics, driven by fundamental experiments like the ones by Young, Fizeau, Michelson-Morley and others. Quantum mechanics, and especially the de Broglie’s postulate relating the momentum p of a particle to the wave vector k of an matter wave: k = 2 λ = p/ℏ, suggested that wave optical experiments should be also possible with massive particles (see table 1), and over the last 40 years electron and neutron interferometers have demonstrated many fundamental aspects of quantum mechanics [1].

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Optics and interferometry with atoms and molecules

The infrared ${\ensuremath{\nu}}_{2}$ band of ${\mathrm{H}}_{3}^{+}$ has been observed. A direct infrared absorption method combining a liquid-nitrogen-cooled multiple-reflection discharge cell and a difference-frequency laser system has been used for the detection. Fifteen absorption lines have been measured in the region of 2950-2450 ${\mathrm{cm}}^{\ensuremath{-}1}$ and assigned. This is the first spectroscopic detection of this fundamental molecular ion in any spectral range.

Observation of the Infrared Spectrum of H 3

THE H+3 ion is widely believed to play an important role in interstellar chemistry, by initiating the chains of reactions that lead to the production of many of the complex molecular species observed in the interstellar medium1–5. The presence of H+3 in the interstellar medium was first suggested6 in 1961, and its infrared spectrum was measured7 in the laboratory in 1980. But attempts8–11 to detect it in interstellar space have hitherto proved unsuccessful. Here we report the detection of H+3 absorption in the spectra of two molecular clouds. Although the present results do not permit an accurate determination of the H+3 abundances, these ions appear nevertheless to be present in sufficient quantities to drive much of the chemistry in molecular clouds. It should soon be possible to obtain more accurate measurements, and thus better quantify the role of ion–neutral reactions in the chemical evolution of molecular clouds.

Detection of H + 3 in interstellar space

Calculation of inertia defect: Part I. General formulation

Echelle spectra of the double-lined spectroscopic binary HD 204827 were obtained on five nights, at a resolving power R = 38,000 and with a S/N = 750 near 6000 A in the final, combined spectrum. The stars show E(B − V) = 1.11 and spectral types near O9.5 V and B0.5 III. A catalog is presented of 380 diffuse interstellar bands (DIBs) measured between 3900 and 8100 A in the stars' spectrum. The central wavelengths, the widths (FWHM), and the equivalent widths of nearly all of the bands are tabulated, along with the minimum uncertainties in the latter. The reliable removal of very weak stellar lines from the catalog, and of some stellar lines from the less severe blends with DIBs, is made generally easy by the highly variable radial velocities of both stars. The principal result of this investigation is that the great majority of the bands in the catalog are very weak and relatively narrow. Typical equivalent widths amount to a few mA, and the bandwidths (FWHM) are most often near 0.55 A. Therefore, most of these DIBs can be detected only in spectra obtained at a resolving power and a S/N at least comparable to those used here. In addition, the anomalous interstellar reddening and the very high value of the ratio N(C2)/E(B − V) seen toward HD 204827 indicate that the physical conditions in one or more of the several interstellar clouds seen in this direction differ significantly from those found toward the prototypical DIB target HD 183143, for example. Probably primarily for these reasons, 113 of the 380 bands (30%) were not detected in four previous modern surveys of the DIBs seen in the spectra of stars other than HD 204827. No preferred wavenumber spacings among the 380 bands are reliably identified which could provide clues to the identities of the large molecules thought to cause the DIBs.

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A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827

Author Institution: Department of Astronomy and Department of Chemistry, University of Illinois at; Urbana-Champaign, Urbana, IL 61801; Gemini Observatory, Hilo, HI 96720; Department of Astronomy \& Astrophysics and Department of Chemistry, University of; Chicago, Chicago, IL 60637

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Takeshi Oka

Papers

Observation of the Infrared Spectrum of H 3

Detection of H + 3 in interstellar space

Calculation of inertia defect: Part I. General formulation

A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827

H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate