Hot Methane Spectra for Astrophysical Applications

Abstract

In this thesis line lists for methane (CH4) are presented. These line lists were obtained at high temperatures (300-1400 oC at 100 oC intervals) by recording infrared emission spectra with a tube furnace to heat to the required temperatures and a Fourier transform spectrometer. The spectra were recorded in the range 800- 3400 cm-1 which includes the four fundamental modes; the bending modes that are composed of a pair of ν2 (e) modes (at 1526 cm-1) and a triply degenerate bending mode, ν4 (a t2 bend at 1306 cm-1) and also the stretching modes that are made up of a single symmetric ν1 (a1 at 2914 cm-1) mode and a triply degenerate antisymmetric C-H stretch, ν3 (a t2 mode at 3020 cm-1). The author analysed previously obtained data and recorded additional spectra at a higher wavenumber range (3000-7000 cm-1). The analysis for this range has not yet been completed. Empircal lower state energies are obtained from these spectra and these have been incorporated into the line lists. The line lists obtained from this work may be used to model the spectra of the atmospheres of exoplanets and brown dwarfs.