Hot methane line lists for exoplanet and brown dwarf atmospheres

TL;DR

This paper provides comprehensive high-temperature methane line lists derived from infrared emission spectra, aiding the modeling of exoplanet and brown dwarf atmospheres by including detailed spectral data across a broad infrared range.

Contribution

It introduces experimentally obtained, calibrated methane line lists at high temperatures, covering a wide infrared spectrum, with empirical lower state energies for improved atmospheric modeling.

Findings

Line lists cover 300-1400°C at twelve temperature intervals

Includes all fundamental vibrational modes and hot bands

Enhanced spectral data for planetary atmosphere simulations

Abstract

We present comprehensive experimental line lists of methane (CH4) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300 - 1400 degC at twelve 100 degC intervals spanning the 960 - 5000 cm-1 (2.0 - 10.4 microns) region of the infrared. This range encompasses the dyad, pentad and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH4 spectra, we have estimated empirical lower state energies (Elow in cm-1) and our values have been incorporated into the line lists along with line positions (cm-1) and calibrated line intensities (S' in cm molecule-1). We expect our hot CH4 line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.