Ahmed F. Al-Refaie

The ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

The ExoMol database (www.exomol.com) provides extensive line lists of molecular transitions which are valid over extended temperature ranges. The status of the current release of the database is reviewed and a new data structure is specified. This structure augments the provision of energy levels (and hence transition frequencies) and Einstein A coefficients with other key properties, including lifetimes of individual states, temperature-dependent cooling functions, Lande g-factors, partition functions, cross sections, k-coefficients and transition dipoles with phase relations. Particular attention is paid to the treatment of pressure broadening parameters. The new data structure includes a definition file which provides the necessary information for utilities accessing ExoMol through its application programming interface (API). Prospects for the inclusion of new species into the database are discussed.

ExoMol line lists – VIII. A variationally computed line list for hot formaldehyde

Acomputedlinelistforformaldehyde,H2 12 C 16 O,applicabletotemperaturesuptoT =1500K is presented. An empirical potential energy and ab initio dipole moment surfaces are used as the input to the nuclear motion program TROVE. The resulting line list, referred to as AYTY, contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies. Each transition includes associated Einstein-Acoefficients and absolute transition intensities,forwavenumbersbelow10000cm −1 androtationalexcitationsuptoJ =70.Roomtemperature spectra are compared with laboratory measurements and data currently available in the HITRAN data base. These spectra show excellent agreement with experimental spectra and highlight the gaps and limitations of the HITRAN data. The full line list is available from the CDS data base as well as at www.exomol.com.

ExoMol line lists XV: A new hot line list for hydrogen peroxide

A computed line list for hydrogen peroxide, H216O2, applicable to temperatures up to T = 1250 K is presented. A semi-empirical high-accuracy potential energy surface is constructed and used with an ab initio dipole moment surface as input TROVE to compute 7.5 million rotational-vibrational states and around 20 billion transitions with associated Einstein-A coefficients for rotational excitations up to J = 85. The resulting APTY line list is complete for wavenumbers below 6000 cm−1 (λ < 1.67 μm) and temperatures up to 1250 K. Room-temperature spectra are compared with laboratory measurements and data currently available in the HITRAN data base and literature. Our rms with line positions from the literature is 0.152 cm−1 and our absolute intensities agree better than 10 per cent. The full line list is available from the CDS data base as well as at www.exomol.com.

G PU A ccelerated IN tensities MPI (GAIN-MPI): A new method of computing Einstein-A coefficients

Abstract Calculating dipole transition intensities or the related Einstein A coefficients can dominate the computer usage for large line lists of transitions such as those being computed to model radiative transport through hot atmospheres. An algorithm for the efficient computation of line strengths is presented based on the use of the half-linestrength. This is implemented on GPUs that are shown to give up to a thousandfold speed-up compared to calculations on conventional computers. This algorithm is implemented in the program GAIN which was developed as part of the TROVE nuclear motion program, but can be adapted for use by other similar programs in a straightforward fashion. Program summary Program title: GAIN-MPI Program Files doi: http://dx.doi.org/10.17632/4x75jsphc6.1 Licensing provisions: MIT licence. Programming language: C++ 99, CUDA C and Fortran 95. Nature of problem: Computation of linestrengths using GPU hardware Solution method : Split the linestrength into smaller blocks and compute them in the GPU in parallel Restrictions: The current version is restricted to separable rovibrational basis sets Unusual features: Can be extended by user supplied concrete C++ classes for the MPI version

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.

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

Abstract Construction and diagonalization of the Hamiltonian matrix is the rate-limiting step in most low-energy electron – molecule collision calculations. Tennyson (1996) 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, photoionization and positron–molecule collisions.