arXiv subjects

Jonathan Tennyson

Publications and source records attributed to Jonathan Tennyson.

At least 37 records · Page 2Linked to original sources

arXiv2025

ExoMolHR: A Relational Database of Empirical High-Resolution Molecular Spectra

ExoMolHR is an empirical, high-resolution molecular spectrum calculator for the high-temperature molecular line lists available from the ExoMol molecular database. Uncertainties, where available, in recommended ExoMol datasets are used to select highly accurate spectral lines. These lines largely rely on empirical energy levels generated through the MARVEL (measured active rotation vibration energy levels) procedure, which is being systematically used to improve the energy and transition data provided by the ExoMol database. The freely accessible ExoMolHR database provides line positions with calculated intensities for a user-specified wavenumber/wavelength range and temperature. Spectra can be plotted on the ExoMolHR website (https://www.exomol.com/exomolhr/) or downloaded as a CSV file. Cross sections can be calculated using the Python program PyExoCross. The ExoMolHR database currently provides 24307135 spectral lines for 33 molecules and 58 isotopologues; these numbers will increase as the ExoMol database is updated.

astro-ph.EP↗

arXiv2025

Empirical rovibrational energy levels for carbon disulfide

An analysis of the measured rovibrational transitions is carried out for the 12C32S2 isotopologue of carbon disulfide. Data from 21 sources is extracted and validated using a consistent set of standard linear molecule quantum numbers. A corrected list of 8714 CS2 transitions forms the input to a Measured Active Rotational-Vibrational Energy Levels (MARVEL) procedure, generating 4279 empirical rovibrational energy levels across 138 bands of 12C32S2. Results are compared to the recent NASA Ames line list. While the agreement is generally good, issues are identified with the energy levels of some states, notably those with high values of the v2 bending quantum number.

physics.atom-ph↗

arXiv2024

ExoMol line lists -- LXIV: Empirical rovibronic spectra of phosphorous mononitride (PN) covering the IR and UV regions

A new phosphorous mononitride (${}^{31}$P${}^{14}$N, ${}^{31}$P${}^{15}$N) line list PaiN covering infrared, visible and ultraviolet regions is presented. The PaiN line list extending to the $A\,{}^{1}Π$ -- $X\,{}^{1}Σ^{+}$ vibronic band system, replaces the previous YYLT ExoMol line list for PN. A thorough analysis of high resolution experimental spectra from the literature involving the $X\,{}^{1}Σ^{+}$ and $A\,{}^{1}Π$ states is conducted, and many perturbations to the $A\,{}^{1}Π$ energies are considered as part of a comprehensive MARVEL study. Ab initio potential energy and coupling curves from the previous work [Semenov et al., Phys. Chem. Chem. Phys., 23, 22057 (2021)] are refined by fitting their analytical representations to 1224 empirical energy levels determined using the MARVEL procedure. The PaiN line list is compared to previously observed spectra, recorded and calculated lifetimes, and previously calculated partition functions. The ab initio transition dipole moment curve for the $A$--$X$ band is scaled to match experimentally measured lifetimes. The line list is suitable for temperatures up to 5000 K and wavelengths longer than 121 nm. PaiN is available from www.exomol.com.

astro-ph.EP↗

arXiv2024

ExoMol line lists -- LXV. Mid-Infrared rovibronic spectroscopy of isotopologues of NiH

New line lists for four isotopologues of nickel monohydride, $^{58}$NiH, $^{60}$NiH, $^{62}$NiH, and $^{58}$NiD are presented covering the wavenumber range $<10000$ cm$^{-1}$ ($λ> 1$ $μ$m), $J$ up to 37.5 for transitions within and between the three lowest-lying electronic states, ${X}\,^{2}Δ$, ${W}\,^{2}Π$, and ${V}\,^{2}Σ^{+}$. The line lists are applicable for temperatures up to 5000 K. The line lists calculations are based on a recent empirical NiH spectroscopic model [Havalyova et al. J. Quant. Spectrosc. Radiat. Transf., 272, 107800, (2021)] which is adapted for the variational nuclear-motion code Duo. The model consists of potential energy curves, spin-orbit coupling curves, electronic angular momentum curves, spin-rotation coupling curves, $Λ$-doubling correction curve for $^2Π$ states and Born-Oppenheimer breakdown (BOB) rotational correction curves. New ab initio dipole moment curves, scaled to match the experimental dipole moment of the ground state, are used to compute Einstein A coefficients. The BYOT line lists are included in the ExoMol database at www.exomol.com.

astro-ph.SR↗

arXiv2024

ExoMol line lists -- LX. Molecular line list for the ammonia isotopologue $^{15}$NH$_3$

A theoretical line list for $^{15}$NH$_3$ CoYuTe-15 is presented based on the empirical potential energy and ab initio dipole moments surfaces developed and used for the production of the ExoMol line list CoYuTe for $^{14}$NH$_3$. The ro-vibrational energy levels and wavefunctions are computed using the variational program TROVE. The line list ranges up to 10000 cm$^{-1}$ ($λ\geq 1$ $μ$m) and contains 929 795 249 transitions between 1 269 961 states with $J\le 30$. The line list should be applicable for temperatures up to $\sim$1000 K. To improve the accuracy of the line positions, a set of experimentally-derived energy levels of $^{15}$NH$_3$ is produced using the MARVEL procedure. To this end, 37 experimental sources of the line positions of $^{15}$NH$_3$ available in the literature are collected, combined and systematised to produce a self-consistent spectroscopic network of 21095 $^{15}$NH$_3$ transitions covering 40 vibrational bands ranging up to 6818 cm$^{-1}$ and resulting in 2777 energy term values. These MARVEL energies are then used to replace the theoretical values in the CoYuTe-15 line list and also complemented by pseudo-MARVEL energies obtained by an isotopologue extrapolation using the previously reported MARVEL energies of the $^{14}$NH$_3$ parent isotopologue of ammonia. A list of 53856 high resolution transitions between MARVEL states and theoretical intensities is provided in the HITRAN format. Comparison with the recent experimental spectra of $^{15}$NH$_3$ illustrate the potential of the line list for detections and as an efficient assistant in spectroscopic assignments. The line list is available from www.exomol.com.

astro-ph.EP↗

arXiv2024

ExoMol line lists -- LIX. High-temperature line list for N$_2$O

New hot line lists for five isotopologues of N$_2$O are presented, for the parent $^{14}$N$_2^{16}$O and 4 singly substituted species $^{14}$N$_2^{17}$O, $^{14}$N$_2^{18}$O, $^{14}$N$^{15}$N$^{16}$O and $^{15}$N$^{14}$N$^{16}$O. The line lists have been computed with the variational program TROVE using a new empirical potential energy surface (PES) and an accurate ab initio dipole moment surface of N$_2$O Ames-1. The PES was obtained by fitting to experimentally derived energies of N$_2$O compiled using the well established MARVEL procedure. Here we also introduce an `artificial symmetry group' $C_{\rm ns}$(AEM) for an efficient construction of rotation-vibrational basis set of a linear non-symmetric triatomic molecule of the XYZ type. The line lists cover the rotational excitations up to $J=160$ and the wavenumber range up to 20000 cm$^{-1}$. MARVEL energies are also used to improve predicted line positions resulting in excellent agreement with the available experimental spectra, as demonstrated. An extensive comparison with existing line lists for N$_2$O HITRAN, HITEMP, NOSL-296, NOSD-1000 and Ames-296K is provided. The line lists are freely accessible from www.exomol.com.

astro-ph.EP↗

arXiv2024

A hybrid approach to generating diatomic line lists for high resolution studies of exoplanets and other hot astronomical objects: Updates to ExoMol MgO, TiO and VO line lists

The best molecular line lists for astrophysical applications today require both high accuracy of line positions for strong lines as well as high overall completeness. The former is required to enable, for example, molecular detection in high-resolution cross-correlation observations of exoplanets, while completeness is required for accurate spectroscopic and radiative properties over broad temperature and spectral ranges. The use of empirical energies generated with the Marvel procedure is a standard way to improve accuracy; here we explore methods of extending the use of these levels using predicted shifts and isotopologue extrapolation, as well augmenting the levels from other sources such as effective Hamiltonian studies. These methods are used to update ExoMol line lists for the main 24Mg16O and 48Ti16O isotopologues, as well as for 24Mg17O, 24Mg18O, 25Mg16O, 26Mg16O, 46Ti16O, 47Ti16O, 49Ti16O and 50Ti16O; new Marvel results for 51V16O are also presented

astro-ph.SR↗

arXiv2024

The 2024 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres

The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. These data are widely used to model atmospheres of exoplanets, cool stars and other astronomical objects, as well as a variety of terrestrial applications. The 2024 data release reports the current status of the database which contains recommended line lists for 91 molecules and 224 isotopologues giving a total of almost 10$^{12}$ individual transitions. New features of the database include extensive "MARVELization" of line lists to allow them to be used for high resolutions studies, extension of several line lists to ultraviolet wavelengths, provision of photodissociation cross sections and extended provision of broadening parameters. Some of the in-house data specifications have been rewritten in JSON and moved to conformity with other international standards. Data products, including specific heats, a database of lifetimes for plasma studies, and the ExoMolHR web app which allows exclusively high resolution data to be extracted, are discussed.

astro-ph.GA↗

arXiv2024

PyExoCross: a Python program for generating spectra and cross-sections from molecular line lists

PyExoCross is a Python adaptation of the ExoCross Fortran application, PyExoCross is designed for postprocessing the huge molecular line lists generated by the ExoMol project and other similar initiatives such as the HITRAN and HITEMP databases. PyExoCross generates absorption and emission stick spectra, cross-sections, and other properties (partition functions, specific heats, cooling functions, lifetimes, and oscillator strengths) based on molecular line lists. PyExoCross calculates cross-sections with four line profiles: Doppler, Gaussian, Lorentzian, and Voigt profiles in both sampling and binned methods; a number of options are available for computing Voigt profiles which we test for speed and accuracy. PyExoCross supports importing and exporting line lists in the ExoMol and HITRAN/HITEMP formats. PyExoCross also provides conversion between the ExoMol and HITRAN data formats. In addition, PyExoCross has extra code for users to automate the batch download of line list files from the ExoMol database.

astro-ph.IM↗

arXiv2024

Predissociation dynamics of the hydroxyl radical (OH) based on a five-state spectroscopic model

Multi-reference configuration interaction (MRCI) potential energy curves (PECs) and spin-orbit couplings for the X $^2Π$, A $^2 Σ^+$, 1 $^2 Σ^-$, 1 $^4 Σ^-$, and 1 $^4 Π$ states of OH are computed and refined against empirical energy levels and transitions to produce a spectroscopic model. Predissociation lifetimes are determined by discretising continuum states in the variational method nuclear motion calculation by restricting the calculation to finite range of internuclear separations. Varying this range give a series of avoided crossings between quasi-bound states associated with the A $^2 Σ^+$ and continuum states, from which predissociation lifetimes are extracted. 424 quasi-bound A $^2 Σ^+$ state rovibronic energy levels are analysed and 374 predissociation lifetimes are produced, offering good coverage of the predissociation region. Agreement with measured lifetimes is satisfactory and a majority of computed results were within experimental uncertainty. A previously unreported A $^2 Σ^+$ state predissociation channel which goes via the X $^2Π$ is identified in the calculations. A python package, binslt, is produced to calculate predissociation lifetimes, associated line broadening parameters, and uncertainties from Duo *.states files is made available. The PECs and other curves from this work will be used to produce a rovibronic ExoMol linelist and temperature-dependent photodissociation cross sections for the hydroxyl radical.

physics.chem-ph↗

arXiv2024

Dissociation of hydrofluorocarbon molecules after electron impact in plasma

The process of dissociation for two hydrofluorocarbon molecules in low triplet states excited by electron impact in plasma is investigated by ab initio Molecular Dynamics (AIMD). The interest in dissociation of hydrofluorocarbons in plasma is motivated by their role in plasma etching in microelectronic technologies. Dissociation of triplet states is very fast, and the reaction products can be predicted. In this work, it was found that higher triplet states relax into the lowest triplet state within a few femtoseconds due to nonadiabatic dynamics, so that the simplest ab initio MD on the lowest triplet state seems to give a reasonable estimate of the reaction channels branching ratios. We provide evidence for the existence of simple rules for the dissociation of hydrofluorocarbon molecules in triplet states. For molecules with a double bond, the bonds adjacent to it dissociate faster than the other bonds.

physics.chem-ph↗

arXiv2024

The impact of spectral line wing cut-off: Recommended standard method with application to MAESTRO opacity database

When computing cross-sections from a line list, the result depends not only on the line strength, but also the line shape, pressure-broadening parameters, and line wing cut-off (i.e., the maximum distance calculated from each line centre). Pressure-broadening can be described using the Lorentz lineshape, but it is known to not represent the true absorption in the far wings. Both theory and experiment have shown that far from the line centre, non-Lorentzian behaviour controls the shape of the wings and the Lorentz lineshape fails to accurately characterize the absorption, leading to an underestimation or overestimation of the opacity continuum depending on the molecular species involved. The line wing cut-off is an often overlooked parameter when calculating absorption cross sections, but can have a significant effect on the appearance of the spectrum since it dictates the extent of the line wing that contributes to the calculation either side of every line centre. Therefore, when used to analyse exoplanet and brown dwarf spectra, an inaccurate choice for the line wing cut-off can result in errors in the opacity continuum, which propagate into the modeled transit spectra, and ultimately impact/bias the interpretation of observational spectra, and the derived composition and thermal structure. Here, we examine the different methods commonly utilized to calculate the wing cut-off and propose a standard practice procedure (i.e., absolute value of 25~cm$^{-1}$ for $P\leqslant$~200~bar and 100~cm$^{-1}$ for $P >$ ~200~bar) to generate molecular opacities which will be used by the open-access {\tt MAESTRO} (Molecules and Atoms in Exoplanet Science: Tools and Resources for Opacities) database. The pressing need for new measurements and theoretical studies of the far-wings is highlighted.

astro-ph.EP↗

arXiv2023

The Numerical Equivalence of Diabatic and Adiabatic Representations in Diatomic Molecules

The (stationary) Schrödinger equation for atomistic systems is solved using the adiabatic potential energy curves (PECs) and the associated adiabatic approximation. Despite being very simplistic, this approach is very powerful and used in nearly all practical applications. In cases when interactions between electronic states become important, the associated non-adiabatic effects are taken into account via the derivative couplings (DDRs), also known as non-adiabatic couplings (NACs). For diatomic molecules, the corresponding PECs in the adiabatic representation are characterized by avoided crossings. The alternative to the adiabatic approach is the diabatic representation, obtained via a unitary transformation of the adiabatic states by minimizing the DDRs. For diatomics, the diabatic representation has zero DDR and non-diagonal diabatic couplings (DCs) ensue. The two representations are fully equivalent and so should be the rovibronic energies and wavefunctions which result from the solution of the corresponding Schrödinger equations. We demonstrate (for the first time), the numerical equivalence between the adiabatic and diabatic rovibronic calculations of diatomic molecules, using the ab initio curves of yttrium oxide (YO) and carbon monohydride (CH) as examples of two-state systems, where YO is characterized by a strong NAC, while CH has a strong diabatic coupling. Rovibronic energies and wavefunctions are computed using a new diabatic module implemented in variational rovibronic code DUO. We show that it is important to include both the Diagonal Born-Oppenheimer Correction (DBOC) and non-diagonal DDRs. We also show that convergence of the vibronic energy calculations can strongly depend on the representation of nuclear motion used and that no one representation is best in all cases.

physics.chem-ph↗

arXiv2023

Collisional broadening of molecular rovibronic lines

To meet burning needs of high-resolution pressure-induced line-shape parameters in the UV/visible regions for hot-temperature industrial and atmospheric applications as well as current and future space missions, phase-shift theory is examined in its historical context, tested and revisited using accurate numerical potentials and advanced trajectory models. First, a general analysis for arbitrary molecular systems is conducted in terms of the dimensionless parameter $α$ determined by the differences of the Lennard-Jones parameters in the final and initial electronic absorber's states. Temperature dependence, use of the power law and influence of Maxwell-Boltzmann averaging over relative velocities are addressed. Then, interaction-potential calculations are attempted for some representative molecular pairs (NO-Ar, NO-N$_2$, OH-Ar and OH-N$_2$) and the isotropic parts are fitted using the 12-6 Lennard-Jones form to get room and high-temperature line-broadening and line-shift coefficients which are compared to available measurements. It is shown that the phase-shift theory in its standard rectilinear-trajectory formulation provides linewidth and shift estimates accurate within 30-40 %. Attempted improvements using numerical potentials and curved trajectories lead to closer matches with measurements for some cases but also worsen the agreement for others. To ensure better theoretical predictions, introduction of correction terms to the usual phase-shift integral is suggested.

physics.ao-ph↗

arXiv2023

ExoMol line lists -- LVI: The SO line list, MARVEL analysis of experimental transition data and refinement of the spectroscopic model

A semi-empirical IR/Vis line list, SOLIS, for the sulphur monoxide molecule $^{32}$S$^{16}$O is presented. SOLIS includes accurate empirical rovibrational energy levels, uncertainties, lifetimes, quantum number assignments, and transition probabilities in the form of Einstein $A$ coefficients covering the $X\,{}^{3}Σ^{-}$, $a\,{}^{1}Δ^{ }$, $b\,{}^{1}Σ^{+}$, $A\,{}^{3}Π$, $B\,{}^{3}Σ^{-}$, $X\,{}^{\prime\prime3}Σ^{+}$, $A\,{}^{\prime 3}Δ$ and $e\,{}^{1}Π$ systems and wavenumber range up to 43303.5 cm$^{-1}$ ($\geq 230.93$ nm) with $J\le 69$. SOLIS has been computed by solving the rovibronic Schrödinger equation for diatomics using the general purpose variational code Duo and starting from a published ab initio spectroscopic model of SO (including potential energy curves, coupling curves, (transition) dipole moment curves) which is refined to experimental data. To this end, a database of 50106 experimental transitions, 48972 being non-redundant, has been compiled through the analysis of 29 experimental sources, and a self-consistent network of 8558 rovibronic energy levels for the $X$, $a$, $b$, $A$, $B$, and $C$ electronic states has been generated with the MARVEL algorithm covering rotational and vibrational quantum numbers $J \leq 69$ and $v \leq 30$ and energies up to 52350.40 cm$^{-1}$. No observed transitions connect to the $ B\,{}^{3}Σ^{-} (v = 0)$ state which is required to model perturbations correctly, so we leave fitting the $B\,{}^3Σ^-$ and $C\,{}^3Π$ state UV model to a future project. The SO line list is available at ExoMol from www.exomol.com.

astro-ph.EP↗

arXiv2023

ExoMol line lists -- LIV: Empirical line lists for AlH and AlD and experimental emission spectroscopy of AlD in $A$ $^1Π$ ($v=0, 1, 2$)

New ExoMol line lists AloHa for AlH and AlD are presented improving the previous line lists WYLLoT (Yurchenko et al., MNRAS 479, 1401 (2018)). The revision is motivated by the recent experimental measurements and astrophysical findings involving the highly excited rotational states of AlH in its $A\,^{1}Π-{X}\,^{1}Σ^{+}$ system. A new high-resolution emission spectrum of ten bands from the ${A}\,^{1}Π-{X}\,^{1}Σ^{+}$ system of AlD, in the region $17300 - 32000$ cm$^{-1}$ was recorded with a Fourier transform spectrometer, which probes the predissociative $A\,^1Π$ $v=2$ state. The AlD new line positions are combined with all available experimental data on AlH and AlD to construct a comprehensive set of empirical rovibronic energies of AlH and AlD covering the $X\,^1Σ^+$ and $A\,^1Π$ electronic states using the MARVEL approach. We then refine the spectroscopic model WYLLoT to our experimentally derived energies using the nuclear-motion code Duo and use this fit to produce improved line lists for $^{27}$AlH, $^{27}$AlD and $^{26}$AlH with a better coverage of the rotationally excited states of $A\,^1Π$ in the predissociative energy region. The lifetimes of the predissociative states are estimated and are included in the line list using the new ExoMol data structure, alongside the temperature-dependent continuum contribution to the photo-absorption spectra of AlH. The new line lists are shown to reproduce the experimental spectra of both AlH and AlD well, and to describe the AlH absorption in the recently reported Proxima Cen spectrum, including the strong predissociative line broadening. The line lists are included into the ExoMol database www.exomol.com.

astro-ph.SR↗

arXiv2023

ExoMol line lists -- LIII: Empirical Rovibronic spectra of Yttrium Oxide (YO)

Empirical line lists for the open shell molecule $^{89}$Y$^{16}$O (yttrium oxide) and its isotopologues are presented. The line lists cover the 6 lowest electronic states: $X {}^{2}Σ^{+}$, $A {}^{2}Π$, $A' {}^{2}Δ$, $B {}^{2}Σ^{+}$, $C {}^{2}Π$ and $D {}^{2}Σ^{+}$ up to 60000 cm$^{-1}$ ($<0.167$ $μ$m) for rotational excitation up to $J = 400.5$. An \textit{ab initio} spectroscopic model consisting of potential energy curves (PECs), spin-orbit and electronic angular momentum couplings is refined by fitting to experimentally determined energies of YO, derived from published YO experimental transition frequency data. The model is complemented by empirical spin-rotation and $Λ$-doubling curves and \textit{ab initio} dipole moment and transition dipole moment curves computed using MRCI. The \textit{ab initio} PECs computed using the complete basis set limit extrapolation and the CCSD(T) method with its higher quality provide an excellent initial approximation for the refinement. Non-adiabatic coupling curves for two pairs of states of the same symmetry $A$/$C$ and $B$/$D$ are computed using a state-averaged CASSCF and used to built diabatic representations for the $A {}^{2}Π$, $C {}^{2}Π$, $B {}^{2}Σ^{+}$ and $D {}^{2}Σ^{+}$ curves. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists for are included into the ExoMol data base (www.exomol.com).

astro-ph.SR↗

arXiv2023

Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm$^{-1}$ range: experimental line list and improved MARVEL analysis

We use optical frequency comb Fourier transform spectroscopy to record high-resolution, low-pressure, room-temperature spectra of formaldehyde (H$_2$$^{12}$C$^{16}$O) in the range of 1250 to 1390 cm$^{-1}$. Through line-by-line fitting, we retrieve line positions and intensities of 747 rovibrational transitions: 558 from the $ν_6$ band, 129 from the $ν_4$ band, and 14 from the $ν_3$ band, as well as 46 from four different hot bands. We incorporate the accurate and precise line positions (0.4 MHz median uncertainty) into the MARVEL (measured active vibration-rotation energy levels) analysis of the H$_2$CO spectrum. This increases the number of MARVEL-predicted energy levels by 82 and of rovibrational transitions by 5382, and substantially reduces uncertainties of MARVEL-derived H$_2$CO energy levels over a large range: from pure rotational levels below 200 cm$^{-1}$ up to multiply excited vibrational levels at 6000 cm$^{-1}$. This work is an important step toward filling the gaps in formaldehyde data in the HITRAN database.

physics.chem-ph↗