Emission spectrum of hot HDO in the 380-2190 cm(-1) region

Fourier transform emission spectra were recorded using a mixture of H2O and D2O at a temperature of 1500 degreesC. The spectra were recorded in three overlapping sections and cover the wavenumber range 380-2190 cm(-1). A total of 22106 lines were measured, of which 60% are thought to belong to HDO. A total of 6430 FIDO transition,, are assigned, including the first transitions to the (040) vibrational state, with a term value of 5420.042 cm(-1). A total of 1536 new energy levels of HDO belonging to the (000), (010) (020), (030), and (040) stated are presented, significantly extending the degree of rotational excitation compared to previous studies. (C) 2001 Elsevier Science

ExoMol line lists - III. An improved hot rotation-vibration line list for HCN and HNC

A revised rotation-vibration line list for the combined hydrogen cyanide (HCN)/hydrogen isocyanide (HNC) system is presented. The line list uses ab initio transition intensities calculated previously and extensive data sets of recently measured experimental energy levels. The resulting line list has significantly more accurate wavelengths than previous ones for these systems. An improved value for the separation between HCN and HNC is adopted, leading to an approximately 25 per cent lower predicted thermal population of HNC as a function of temperature in the key 2000 to 3000 K region. Temperature-dependent partition functions and equilibrium constants are presented. The line lists are validated by comparison with laboratory spectra and are presented in full as supplementary data to the article and at www.exomol.com

A room temperature CO2 line list with ab initio computed intensities

Atmospheric carbon dioxide concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5% or better. We report a theoretical study providing rotation-vibration line intensities substantially within the required accuracy based on the use of a highly accurate ab initio dipole moment surface (DMS). The theoretical model developed is used to compute CO2 intensities with uncertainty estimates informed by cross comparing line lists calculated using pairs of potential energy surfaces (PES) and DMS's of similar high quality. This yields lines sensitivities which are utilized in reliability analysis of our results. The final outcome is compared to recent accurate measurements as well as the HITRAN2012 database. Transition frequencies are obtained from effective Hamiltonian calculations to produce a comprehensive line list covering all 12C16O2 transitions below 8000cm-1 and stronger than 10-30cm/ molecule at T=296K

Potential energy surface, dipole moment surface and the intensity calculations for the 10 µm, 5 µm and 3 µm bands of ozone

Monitoring ozone concentrations in the Earth's atmosphere using spectroscopic methods is a major activity which undertaken both from the ground and from space. However there are long-running issues of consistency between measurements made at infrared (IR) and ultraviolet (UV) wavelengths. In addition, key O 3 IR bands at 10 µm, 5 µm and 3 µm also yield results which differ by a few percent when used for retrievals. These problems stem from the underlying laboratory measurements of the line intensities. Here we use quantum chemical techniques, first principles electronic structure and variational nuclear-motion calculations, to address this problem. A new high-accuracy ab initio dipole moment surface (DMS) is computed. Several spectroscopically-determined potential energy surfaces (PESs) are constructed by fitting to empirical energy levels in the region below 7000 cm−1 starting from an ab initio PES. Nuclear motion calculations using these new surfaces allow the unambiguous determination of the intensities of 10 µm band transitions, and the computation of the intensities of 10 µm and 5 µm bands within their experimental error. A decrease in intensities within the 3 µm is predicted which appears consistent with atmospheric retrievals. The PES and DMS form a suitable starting point both for the computation of comprehensive ozone line lists and for future calculations of electronic transition intensities

ExoMol molecular line lists XIX: high-accuracy computed hot line lists for H218O and H217O

Hot line lists for two isotopologues of water, H218O and H217O, are presented. The calculations employ newly constructed potential energy surfaces (PES), which take advantage of a novel method for using the large set of experimental energy levels for H216O to give high-quality predictions for H218O and H217O. This procedure greatly extends the energy range for which a PES can be accurately determined, allowing an accurate prediction of higher lying energy levels than are currently known from direct laboratory measurements. This PES is combined with a high-accuracy, ab initio dipole moment surface of water in the computation of all energy levels, transition frequencies and associated Einstein A coefficients for states with rotational excitation up to J = 50 and energies up to 30 000 cm−1. The resulting HotWat78 line lists complement the well-used BT2 H216O line list. Full line lists are made available online as Supporting Information and at www.exomol.com

A variationally calculated room temperature line-list for H2O2

A room temperature line list for hydrogen peroxide is computed using a high level ab initio potential energy surface by Małyszek and Koput (2013) with a small adjustment of the equilibrium geometry and height of the torsional barrier and a new ab initio dipole moment surface (CCSD(T)-f12b/aug-cc-pv(T+d)Z). In order to improve further the ab initio accuracy, the vibrational band centers were shifted to match experimental values when available. The line list covers the wavenumber region up to 8000 cm−1 with the rotational excitations J⩽40. Room temperatures synthetic spectra of H2O2 are generated and compared to the spectra from the HITRAN and PNNL-IR databases showing good agrement

Room temperature line lists for CO2 symmetric isotopologues with ab initio computed intensities

Remote sensing experiments require high-accuracy, preferably sub-percent, line intensities and in response to this need we present computed room temperature line lists for six symmetric isotopologues of carbon dioxide: 13C16O2, 14C16O2, 12C17O2, 12C18O2, 13C17O2 and 13C18O2, covering the range 0–8000 cm−1. Our calculation scheme is based on variational nuclear motion calculations and on a reliability analysis of the generated line intensities. Rotation–vibration wavefunctions and energy levels are computed using the DVR3D software suite and a high quality semi-empirical potential energy surface (PES), followed by computation of intensities using an ab initio dipole moment surface (DMS). Four line lists are computed for each isotopologue to quantify sensitivity to minor distortions of the PES/DMS. Reliable lines are benchmarked against recent state-of-the-art measurements and against the HITRAN2012 database, supporting the claim that the majority of line intensities for strong bands are predicted with sub-percent accuracy. Accurate line positions are generated using an effective Hamiltonian. We recommend the use of these line lists for future remote sensing studies and their inclusion in databases

ExoMol molecular line lists – XX. A comprehensive line list for H3+

H3+ is a ubiquitous and important astronomical species whose spectrum has been observed in the interstellar medium, planets and tentatively in the remnants of supernova SN1897a. Its role as a cooler is important for gas giant planets and exoplanets, and possibly the early Universe. All this makes the spectral properties, cooling function and partition function of H3+ key parameters for astronomical models and analysis. A new high-accuracy, very extensive line list for H3+ called MiZATeP was computed as part of the ExoMol project alongside a temperature-dependent cooling function and partition function as well as lifetimes for excited states. These data are made available in electronic form as supplementary data to this article and at www.exomol.com

Water line intensities in the near-infrared and visible

Water is the single most important molecule for models of the earth's atmosphere but line parameters for water, particularly at shorter wavelengths, are difficult to measure reliably. We suggest that the most reliable way of generating water line parameters is to combine data obtained from a variety of sources, thereby separating line parameter determination into results for strong lines, for weak lines and for isotopically substituted water. Theoretical considerations which are addressed include line assignments and labeling of energy levels and the prospects of a full theoretical solution to the water vapor problem. Particular attention is paid to strong line absorption intensities in the near-infrared where recent studies have given significantly different results. The experimental data used to construct the ESA-WVR linelist (J. Mol. Spectrosc. 208 (2001) 32) is re-analyzed with a focus on effects due to pressure determination in the cell, subtraction of the baseline and parameterization of the line profiles. A preliminary re-analysis suggests that the line intensities given by the ESA-WVR study should be closer to those of Brown et al. (J. Mol. Spectrosc. 212 (2002) 57) used in the HITRAN. This shows the vital importance of validating the data for water by independent means. (C) 2003 Elsevier Ltd. All rights reserved

Room temperature line lists for deuterated water

Line lists are presented for six deuterated isotopologues of water vapor namely HD16O, HD17O, HD18O, D16 2 O, D17 2 O and D18 2 O. These line lists are prepared using empirically-determined energy levels, where available, to provide transition frequencies and high-quality ab initio dipole moment surfaces to provide transition intensities. The reliability of the predicted intensities is tested by computing multiple line lists and analyzing the stability of the results. The resulting intensities are expected to be accurate to a few percent for well-behaved, stable transitions. Complete T = 296 K line lists are provided for each species