scholarly journals ExoMol molecular line lists – XXXIII. The spectrum of Titanium Oxide

2019 ◽  
Vol 488 (2) ◽  
pp. 2836-2854 ◽  
Author(s):  
Laura K McKemmish ◽  
Thomas Masseron ◽  
H Jens Hoeijmakers ◽  
Víctor Pérez-Mesa ◽  
Simon L Grimm ◽  
...  
Keyword(s):  
Ab Initio ◽  
Titanium Oxide ◽  
Extrasolar Planets ◽  
Energy Levels ◽  
M Dwarfs ◽  
Molecular Line ◽  
Line List ◽  
Line Intensities ◽  
Data Centre ◽  
O 47

ABSTRACT Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extrasolar planets. This paper presents a new line database Toto for the main isotopologues of titanium oxide (TiO): $^{46}\text{Ti}^{16}\text{O}$, $^{47}\text{Ti}^{16}\text{O}$, $^{48}\text{Ti}^{16}\text{O}$, $^{49}\text{Ti}^{16}\text{O}$, and $^{50}\text{Ti}^{16}\text{O}$. The $^{48}\text{Ti}^{16}\text{O}$ line list contains transitions with wave-numbers up to 30 000 cm−1, i.e. longwards of 0.33 μm. The Toto line list includes all dipole-allowed transitions between 13 low-lying electronic states (X 3Δ, a1Δ, d 1Σ+, E 3Π, A 3Φ, B3Π, C 3Δ, b 1Π, c1Φ, f1Δ, e 1Σ+). Ab initio potential energy curves (PECs) are computed at the icMRCI level and combined with spin–orbit and other coupling curves. These PECs and couplings are iteratively refined to match known empirical energy levels. Accurate line intensities are generated using ab initio dipole moment curves. The Toto line lists are appropriate for temperatures below 5000 K and contain 30 million transitions for $^{48}\text{Ti}^{16}\text{O}$; it is made available in electronic form via the CDS data centre and via www.exomol.com. Tests of the line lists show greatly improved agreement with observed spectra for objects such as M-dwarfs GJ876 and GL581.

scholarly journals ExoMol line list – XXXIV. A rovibrational line list for phosphinidene (PH) in its $X\, {}^3\Sigma ^-$ and $a\, {}^1\Delta$ electronic states

2019 ◽  
Vol 488 (2) ◽  
pp. 2332-2342 ◽  
Author(s):  
Jonathan Langleben ◽  
Jonathan Tennyson ◽  
Sergei N Yurchenko ◽  
Peter Bernath
Keyword(s):  
Ab Initio ◽  
Electronic States ◽  
Stellar Atmospheres ◽  
Spin Splitting ◽  
Mean Square ◽  
Data Bases ◽  
Line List ◽  
Line Intensities ◽  
Experimental Transition ◽  
Correction Terms

ABSTRACT A rovibronic line list for the ground (X 3Σ−) and first excited (a 1Δ) states of phosphinidene, 31PH, is computed. The line list is designed for studies of exoplanetary and cool stellar atmospheres with temperatures up to 4000 K. A combination of empirical and ab initio data is used to produce the line list: potential energy curves (PECs) are fitted using experimental transition frequencies; these transitions are reproduced with a root mean square error of 0.01 cm−1. The nuclear Schrödinger equation is solved using these PECs plus Born–Oppenheimer and spin splitting correction terms. Line intensities and Einstein   A coefficients are computed using ab initio dipole moment curves for X–X and a–a transitions. The resulting LaTY line list, which contains 65 055 transitions for 2528 rovibronic states up to 24 500 cm −1 and J = 80, is used to simulate spectra in emission and absorption for a range of temperatures. The line list is made available in electronic form at the CDS and ExoMol data bases.

scholarly journals Computation of Opacities for Diatomic Molecules

1994 ◽  
Vol 146 ◽  
pp. 282-295 ◽  
Author(s):  
Robert L. Kurucz
Keyword(s):  
Distribution Function ◽  
Least Squares ◽  
Diatomic Molecules ◽  
Energy Levels ◽  
Published Data ◽  
Molecular Line ◽  
Model Calculations ◽  
Line List ◽  
Thomas Fermi ◽  
Atomic Lines

In this section I briefly describe my efforts to improve the atomic and molecular line data. This work is described in more detail in Kurucz (1992a). In subsequent sections I briefly describe three methods for computing opacity and the models and spectra that result from using them.My model calculations in the 1970s used the distribution-function line opacity computed by Kurucz (1979a,b) from the line data of Kurucz & Peytremann (1975). We had computedgfvalues for 1.7 million atomic lines for sequences up through nickel using scaled-Thomas-Fermi-Dirac wavefunctions and eigenvectors determined from least squares Slater parameter fits to the observed energy levels. We also collected all published data ong fvalues and included them in the line list whenever they appeared to be more reliable than the computed data (that work is ongoing, but I am running behind).

scholarly journals Molecular Data for Stellar Opacities

1995 ◽  
Vol 10 ◽  
pp. 576-578
Author(s):  
Uffe Gråe Jørgensen
Keyword(s):  
Ab Initio ◽  
Energy Levels ◽  
Laboratory Data ◽  
Molecular Data ◽  
Molecular Ions ◽  
Molecular Constants ◽  
Excitation Energies ◽  
Line Intensities ◽  
Lower Accuracy ◽  
Ab Initio Computations

In total, 40 neutral diatomic molecules, 2 molecular ions, and 7 polyatomic molecules are known from observed photospheric stellar spectra. Line data for opacity computations (i.e., lists of line frequencies, intensities, and excitation energies) exist for 17 of these molecules, although the data are complete only for a handful of them. A detailed description of stellar photospheric molecules can be found in Tsuji (1986), and the existing opacity data have been reviewed by Jorgensen (1995).Listed line frequencies in the data bases are either the measured values, or based on computed molecular constants obtained from fits to measured values. Attempts to compute ab initio line frequencies have so far resulted in lower accuracy than what is obtained by use of molecular constants. Published line strengths include measured values as well as ab initio values. For strong bands the ab initio intensities are as accurate as the laboratory values, whereas measured values for weak bands are generally more accurate than the ab initio values. The primary advantage of ab initio computations is therefore that the complete set of all transitions can be obtained. Exploratory studies have shown that completeness of the line data is crucial for the obtained stellar photospheric structure.As an alternative to the ab initio computations of the line intensities, fits to experimental data have been attempted. The most promising method seems to be to fit the dipole function by use of a Padé approximant. Combined with a potential fitted to experimental energy levels, such a dipole function can in principle be used to predict the complete list of band intensities and line intensities for all bands with energies up to the molecular dissociation energy. The part of the dipole function which corresponds to the largest stretching (or bending) of the molecule is the most uncertain in such fits as well as in ab initio computations. This part is responsible for most of the many weak transitions, and large uncertainties are therefore to be excepted in the computed intensities of the weak spectral bands. As these are of major importance for the stellar photospheric structure (due to their huge number and their pseudo continuous appearance in the spectrum), a particularly large effort is desirable in comparing computed intensities with laboratory data for a representative sample of weak bands. Unfortunately, only few measurements of weak bands exist.

scholarly journals ExoMol molecular line lists – XXXV. A rotation-vibration line list for hot ammonia

2019 ◽  
Vol 490 (4) ◽  
pp. 4638-4647 ◽  
Author(s):  
Phillip A Coles ◽  
Sergei N Yurchenko ◽  
Jonathan Tennyson
Keyword(s):  
Experimental Data ◽  
Dipole Moment ◽  
High Temperature ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Data Base ◽  
Energy Surface ◽  
Molecular Line ◽  
Line List

ABSTRACT A new hot line list for 14NH3 is presented. The line list CoYuTe was constructed using an accurate, empirically refined potential energy surface and a CCSD(T)/aug-cc-pVQZ ab initio dipole moment surface of ammonia, previously reported. The line list is an improvement of the ammonia line list BYTe. The CoYuTe line list covers wavenumbers up to 20 000 cm−1, i.e. wavelengths beyond 0.5 μm for temperatures up to 1500 K. Comparisons with the high temperature experimental data from the literature show excellent agreement for wavenumbers below 6000 cm−1. The CoYuTe line list contains 16.9 billion transitions and is available from the ExoMol website (www.exomol.com) and the CDS data base.

scholarly journals ExoMol molecular line lists – XXXVII. Spectra of acetylene

2020 ◽  
Vol 493 (2) ◽  
pp. 1531-1545 ◽  
Author(s):  
Katy L Chubb ◽  
Jonathan Tennyson ◽  
Sergei N Yurchenko
Keyword(s):  
Angular Momentum ◽  
High Temperature ◽  
Electronic State ◽  
Energy Levels ◽  
Stellar Atmospheres ◽  
Ground Electronic State ◽  
Data Bases ◽  
Molecular Line ◽  
Line List ◽  
Maximum Value

ABSTRACT A new ro-vibrational line list for the ground electronic state of the main isotopologue of acetylene, 12C2H2, is computed as part of the ExoMol project. The aCeTY line list covers the transition wavenumbers up to 10 000 cm−1 (λ > 1 $\mu$m), with lower and upper energy levels up to 12 000 and 22 000 cm−1 considered, respectively. The calculations are performed up to a maximum value for the vibrational angular momentum, Kmax = Lmax  =  16, and maximum rotational angular momentum, J = 99. Higher values of J were not within the specified wavenumber window. The aCeTY line list is considered to be complete up to 2200 K, making it suitable for use in characterizing high-temperature exoplanet or cool stellar atmospheres. Einstein-A coefficients, which can directly be used to calculate intensities at a particular temperature, are computed for 4.3 billion (4 347 381 911) transitions between 5 million (5 160 803) energy levels. We make comparisons against other available data for 12C2H2, and demonstrate this to be the most complete line list available. The line list is available in electronic form from the online CDS and ExoMol data bases.

scholarly journals High-accuracy water potential energy surface for the calculation of infrared spectra

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170149 ◽  
Author(s):  
Irina I. Mizus ◽  
Aleksandra A. Kyuberis ◽  
Nikolai F. Zobov ◽  
Vladimir Yu. Makhnev ◽  
Oleg L. Polyansky ◽  
...  
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Small Molecules ◽  
Potential Energy Surfaces ◽  
Energy Surface ◽  
Energy Levels ◽  
High Accuracy ◽  
Wave Functions ◽  
Line Intensities ◽  
Energy Surfaces

Transition intensities for small molecules such as water and CO 2 can now be computed with such high accuracy that they are being used to systematically replace measurements in standard databases. These calculations use high-accuracy ab initio dipole moment surfaces and wave functions from spectroscopically determined potential energy surfaces (PESs). Here, an extra high-accuracy PES of the water molecule (H 2 16 O) is produced starting from an ab initio PES which is then refined to empirical rovibrational energy levels. Variational nuclear motion calculations using this PES reproduce the fitted energy levels with a standard deviation of 0.011 cm −1 , approximately three times their stated uncertainty. The use of wave functions computed with this refined PES is found to improve the predicted transition intensities for selected (problematic) transitions. A new room temperature line list for H 2 16 O is presented. It is suggested that the associated set of line intensities is the most accurate available to date for this species. This article is part of the theme issue ‘Modern theoretical chemistry’.

scholarly journals ExoMol line lists – XLI. High-temperature molecular line lists for the alkali metal hydroxides KOH and NaOH

2021 ◽  
Author(s):  
A Owens ◽  
J Tennyson ◽  
S N Yurchenko
Keyword(s):  
High Temperature ◽  
Alkali Metal ◽  
First Principles ◽  
Spectroscopic Data ◽  
Potassium Hydroxide ◽  
Energy Levels ◽  
Rotational Excitation ◽  
Molecular Line ◽  
Metal Hydroxides ◽  
Line List

Abstract Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are expected to occur in the atmospheres of hot rocky super-Earth exoplanets but a lack of spectroscopic data is hampering their potential detection. Using robust first-principles methodologies, comprehensive molecular line lists for KOH and NaOH that are applicable for temperatures up to T = 3500 K are presented. The KOH OYT4 line list covers the 0 – 6000 cm−1 (wavelengths λ > 1.67 μm) range and comprises 38 billion transitions between 7.3 million energy levels with rotational excitation up to J = 255. The NaOH OYT5 line list covers the 0 – 9000 cm−1 (wavelengths λ > 1.11 μm) range and contains almost 50 billion lines involving 7.9 million molecular states with rotational excitation up to J = 206. The OYT4 and OYT5 line lists are available from the ExoMol database at www.exomol.com and should greatly aid the study of hot rocky exoplanets.

Ab initio study of the isomerization HNC → HCN. I. Ab initio calculation of the HNC ⇌ HCN potential surface and the corresponding energy levels

1983 ◽  
Vol 82 (3) ◽  
pp. 317-336 ◽  
Author(s):  
Miljenko Perić ◽  
Mirjana Mladenović ◽  
Sigrid D. Peyerimhoff ◽  
Robert J. Buenker
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Potential Surface ◽  
Energy Levels ◽  
Ab Initio Study
Sign in / Sign up

Export Citation Format

Share Document