arXiv subjects

Ahmed F. Al-Refaie

Publications and source records attributed to Ahmed F. Al-Refaie.

22 records · Page 2Linked to original sources

arXiv2016

ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO$_3$

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 $μ$m ($ν< 5000$ 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}.

astro-ph.EP↗

arXiv2016

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

A computed line list for hydrogen peroxide, H$_2{}^{16}$O$_2$, applicable to temperatures up to $T=1250$~K is presented. A semi-empirical high accuracy potential energy surface is constructed and used with an {\it 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 6~000 cm$^{-1}$ ($λ< 1.67$~$μ$m) and temperatures up to 1250~K. Room-temperature spectra are compared with laboratory measurements and data currently available in the HITRAN database and literature. Our rms with line positions from the literature is 0.152 \cm\ and our absolute intensities agree better than 10\%. The full line list is available from the CDS databas

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arXiv2015

ExoMol line lists VIII: A variationally computed line list for hot formaldehyde

A computed line list for formaldehyde, H$_2{}^{12}$C$^{16}$O, applicable to temperatures up to $T=1500$~K is presented. An empirical potential energy and {\it ab initio} dipole moment surfaces are used as the input to nuclear motion program TROVE. The resulting line list, referred to as \textit{AYTY}, contains 10.3 million rotational-vibrational states and around 10 billion transition frequencies. Each transition includes associated Einstein-$A$ coefficients and absolute transition intensities, for wavenumbers below 10~000 cm$^{-1}$ and rotational excitations up to $J=70$. Room-temperature spectra are compared with laboratory measurements and data currently available in the HITRAN database. 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 database as well as at \url{www.exomol.com}.

astro-ph.GA↗

arXiv2014

ExoMol line lists VII: The rotation-vibration spectrum of phosphine up to 1500 K

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~$μ$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 Schrödinger 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}.

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