Showing papers by "Ahmed Al-Refaie published in 2015"
TL;DR: In this article, a comprehensive hot line list is calculated for the ground electronic state of a star, called SAlTY, which contains almost 16.8 billion transitions between 7.5 million energy levels and is suitable for simulating spectra up to temperatures of 1500~K.
Abstract: A comprehensive hot line list is calculated for $^{31}$PH$_3$ in its ground electronic state. This line list, called SAlTY, contains almost 16.8 billion transitions between 7.5 million energy levels and it is suitable for simulating spectra up to temperatures of 1500~K. It covers wavelengths longer than 1~$\mu$m and includes all transitions to upper states with energies below $hc \cdot 18\,000$~cm$^{-1}$ and rotational excitation up to $J=46$. The line list is computed by variational solution of the Schr\"odinger equation for the rotation-vibration motion employing the nuclear-motion program TROVE. A previously reported {\it ab initio} dipole moment surface is used as well as an updated `spectroscopic' potential energy surface (PES), obtained by refining an existing \textit{ab initio} surface through least-squares fitting to the experimentally derived energies. Detailed comparisons with other available sources of phosphine transitions confirms SAlTY's accuracy and illustrates the incompleteness of previous experimental and theoretical compilations for temperatures above 300 K. Atmospheric models are expected to severely underestimate the abundance of phosphine in disequilibrium environments, and it is predicted that phosphine will be detectable in the upper troposphere of many substellar objects. This list is suitable for modelling atmospheres of many astrophysical environments, namely carbon stars, Y dwarfs, T dwarfs, hot Jupiters and solar system gas giant planets. It is available in full as supplementary data to the article and at \url{www.exomol.com}.
132 citations
TL;DR: In this article, an empirical potential energy and ab initio dipole moment surfaces are used as the input to the nuclear motion program TROVE, which contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies.
Abstract: 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.
70 citations
TL;DR: In this article, a room temperature line list for hydrogen peroxide is computed using a high level ab initio potential energy surface by Malyszek and Koput, with a small adjustment of the equilibrium geometry and height of the torsional barrier.
40 citations
22 Jun 2015
1 citations
22 Jun 2015
TL;DR: AYTY as discussed by the authors is a line list for formaldehyde applicable to temperatures up to 1500 K. The line list was computed using the variational ro-vibrational solver TROVE with a refined ab-initio potential energy surface and dipole moment surface.
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 (H2CO) 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 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 ab-initio potential energy surface and dipole moment surface.