ExoMol molecular line lists - XXVII: spectra of C2H4

A new line list for ethylene, $^{12}$C$_2$$^1$H$_4$ is presented. The line list is based on high level ab initio potential energy and dipole moment surfaces. The potential energy surface is refined by fitting to experimental energies. The line list covers the range up to 7000 cm$^{-1}$ (1.43 $\mu$m) with all ro-vibrational transitions (50 billion) with the lower state below 5000 cm$^{-1}$ included and thus should be applicable for temperatures up to 700 K. A technique for computing molecular opacities from vibrational band intensities is proposed and used to provide temperature dependent cross sections of ethylene for shorter wavelength and higher temperatures. When combined with realistic band profiles (such as the proposed three-band model), the vibrational intensity technique offers a cheap but reasonably accurate alternative to the full ro-vibrational calculations at high temperatures and should be reliable for representing molecular opacities. The C$_2$H$_4$ line list, which is called MaYTY, is made available in electronic form from the CDS.