A parallel algorithm for Hamiltonian matrix construction in electron-molecule collision calculations: MPI-SCATCI

Construction and diagonalization of the Hamiltonian matrix is the rate-limiting step in most low-energy electron -- molecule collision calculations. Tennyson (J Phys B, 29 (1996) 1817) implemented a novel algorithm for Hamiltonian construction which took advantage of the structure of the wavefunction in such calculations. This algorithm is re-engineered to make use of modern computer architectures and the use of appropriate diagonalizers is considered. Test calculations demonstrate that significant speed-ups can be gained using multiple CPUs. This opens the way to calculations which consider higher collision energies, larger molecules and / or more target states. The methodology, which is implemented as part of the UK molecular R-matrix codes (UKRMol and UKRMol+) can also be used for studies of bound molecular Rydberg states, photoionisation and positron-molecule collisions.Comment: Write up of a computer program MPI-SCATCI Computer Physics Communications, in pres

ExoCross: a general program for generating spectra from molecular line lists

ExoCross is a Fortran code for generating spectra (emission, absorption) and thermodynamic properties (partition function, specific heat etc.) from molecular line lists. Input is taken in several formats, including ExoMol and HITRAN formats. ExoCross is efficiently parallelized showing also a high degree of vectorization. It can work with several line profiles such as Doppler, Lorentzian and Voigt and support several broadening schemes. Voigt profiles are handled by several methods allowing fast and accurate simulations. Two of these methods are new. ExoCross is also capable of working with the recently proposed method of super-lines. It supports calculations of lifetimes, cooling functions, specific heats and other properties. ExoCross can be used to convert between different formats, such as HITRAN, ExoMol and Phoenix. It is capable of simulating non-LTE spectra using a simple two-temperature approach. Different electronic, vibronic or vibrational bands can be simulated separately using an efficient filtering scheme based on the quantum numbers

AYTY: A NEW LINE-LIST FOR HOT FORMALDEHYDE

begin{abstract} The ExoMol [1] project aims at providing spectroscopic data for key molecules that can be used to characterize the atmospheres of exoplanets and cool stars. Formaldehyde (H$_{2}$CO) is of growing importance in studying and modelling terrestrial atmospheric chemistry and dynamics. It also has relevance in astrophysical phenomena that include interstellar medium abundance, proto-planetary and cometary ice chemistry and masers from extra-galactic sources. However there gaps in currently available absolute intensities and a lack of higher rotational excitations that makes it unfeasible to accurately model high temperature systems such as hot Jupiters. Here we present textbf{AYTY} [2], a new line list for formaldehyde applicable to temperatures up to 1500 $K$. AYTY contains almost 10 million states reaching rotational excitations up to $J=70$ and over 10 billion transitions at up to 10 000 cm$^{-1}$. The line list was computed using the variational ro-vibrational solver TROVE with a refined textit{ab-initio} potential energy surface and dipole moment surface. end{abstract} begin{thebibliography}{1} bibitem{jt528} J.~Tennyson and S.~N. Yurchenko. newblock {em MNRAS}, 425:21--33, 2012. bibitem{jt597} A.~F. Al-Refaie, S.~N. Yurchenko, A.~Yachmenev, and J.~Tennyson. newblock {em MNRAS}, 2015. end{thebibliography

GPU ACCELERATED INTENSITIES: A NEW METHOD OF COMPUTING EINSTEIN-A COEFFICIENTS

begin{abstract} The use of variational nuclear motion calculations to produce comprehensive molecular line lists is now becoming common. In order to produce high quality and complete line-lists in particular applicable to high temperatures requires large amounts of computational resources. The more accuracy required, the larger the problem and the more computational resources needed. The two main bottlenecks in the production of these line-lists are solving the eigenvalue problem and the computation of the Einstein-A coefficients. From the project's recently released line-lists, the number of transitions can reach up to 10 billion evaluated by the combination of millions of eigenvalues and eigenvectors corresponding to individual energy states. For line-lists of this size, the evaluation of Einstein-A coefficients take up the vast majority of computational time compared to solving the eigenvalue problem. Recently, as part of the ExoMol [1] project, we have developed a new program called textbf{G}PU textbf{A}ccelerated textbf{IN}tensities (GAIN) that utilises the highly parallel Graphics Processing Units (GPU) in order to accelerate the evaluation of the Einstein-A coefficients. Speed-ups of up to 70x can be achieved on a single GPU and can be further improved by utilising multiple GPUs. The GPU hardware, its limitations and how the problem was implemented to exploit parallelism will be discussed. end{abstract} begin{thebibliography}{1} bibitem{jt528} J.~Tennyson and S.~N. Yurchenko. newblock {ExoMol: molecular line lists for exoplanet and other atmospheres}. newblock {em MNRAS}, 425:21--33, 2012. end{thebibliography

ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO3_3

Sulphur trioxide (SO$_3$) is a trace species in the atmospheres of the Earth and Venus, as well as well as being an industrial product and an environmental pollutant. A variational line list for $^{32}$S$^{16}$O$_{3}$, named UYT2, is presented containing 21 billion vibration-rotation transitions. UYT2 can be used to model infrared spectra of SO$_3$ at wavelengths longwards of 2 $\mu$m ($\nu < 5000$ cm$^{-1}$) for temperatures up to 800 K. Infrared absorption cross sections are also recorded at 300 and 500 C are used to validate the UYT2 line list. The intensities in UYT2 are scaled to match the measured cross sections. The line list is made available in electronic form as supplementary data to this article and at \url{www.exomol.com}.Comment: 15 pages, 10 figures, 9 tables MNRAS submitte

FRECKLL: Full and Reduced Exoplanet Chemical Kinetics distiLLed

We introduce a new chemical kinetic code FRECKLL (Full and Reduced Exoplanet Chemical Kinetics distiLLed) to evolve large chemical networks efficiently. FRECKLL employs `distillation' in computing the reaction rates, which minimizes the error bounds to the minimum allowed by double precision values ($\epsilon \leq 10^{-15}$). FRECKLL requires less than 5 minutes to evolve the full Venot2020 network in a 130 layers atmosphere and 30 seconds to evolve the Venot2020 reduced scheme. Packaged with FRECKLL is a TauREx 3.1 plugin for usage in forward modelling and retrievals. We present TauREx retrievals performed on a simulated HD189733 JWST spectra using the full and reduced Venot2020 chemical networks and demonstrate the viability of total disequilibrium chemistry retrievals and the ability for JWST to detect disequilibrium processes.Comment: 13 pages, 8 figure

Detectability of Rocky-Vapour Atmospheres on Super-Earths with Ariel

Ariel will mark the dawn of a new era as the first large-scale survey characterising exoplanetary atmospheres with science objectives to address fundamental questions about planetary composition, evolution and formation. In this study, we explore the detectability of atmospheres vaporised from magma oceans on dry, rocky Super-Earths orbiting very close to their host stars. The detection of such atmospheres would provide a definitive piece of evidence for rocky planets but are challenging measurements with currently available instruments due to their small spectral signatures. However, some of the hottest planets are believed to have atmospheres composed of vaporised rock, such as Na and SiO, with spectral signatures bright enough to be detected through eclipse observations with planned space-based telescopes. In this study, we find that rocky super-Earths with a irradiation temperature of 3000 K and a distance from Earth of up to 20 pc, as well as planets hotter than 3500 K and closer than 50 pc, have SiO features which are potentially detectable in eclipse spectra observed with Ariel.Comment: 12 pages, 8 figures, accepted for publication in Experimental Astronomy, Ariel Special Issu

YunMa: Enabling Spectral Retrievals of Exoplanetary Clouds

In this paper, we present YunMa, an exoplanet cloud simulation and retrieval package, which enables the study of cloud microphysics and radiative properties in exoplanetary atmospheres. YunMa simulates the vertical distribution and sizes of cloud particles and their corresponding scattering signature in transit spectra. We validated YunMa against results from the literature. When coupled to the TauREx 3 platform, an open Bayesian framework for spectral retrievals, YunMa enables the retrieval of the cloud properties and parameters from transit spectra of exoplanets. The sedimentation efficiency (f sed), which controls the cloud microphysics, is set as a free parameter in retrievals. We assess the retrieval performances of YunMa through 28 instances of a K2-18 b-like atmosphere with different fractions of H2/He and N2, and assuming water clouds. Our results show a substantial improvement in retrieval performances when using YunMa instead of a simple opaque cloud model and highlight the need to include cloud radiative transfer and microphysics to interpret the next-generation data for exoplanet atmospheres. This work also inspires instrumental development for future flagships by demonstrating retrieval performances with different data quality