The dissociative photoionization of methane in the VUV

AM Sands, RA Mackie, N Kouchi+, KF Dunn and CJ Latimer

Department of Pure and Applied Physics, The Queen's University of Belfast,Belfast 
BT7 1NN, UK.
+Department of Chemistry, Tokyo Institute of Technology, Meguro-ku, Tokyo 152, Japan

The dissociative photoionization of CH4 and CD4 has been studied using synchrotron 
radiation within the energy range 12- 60eV.  The mass spectra of secondary ions have 
been found to display significant isotope effects and to depend on the target gas 
temperature.  The kinetic energy spectra of the fragment protons and deuterons has 
also been determined and it is shown that , in addition  to direct 
photoionization, intermediate superexcited states play an important role in the 
photodissociative ionization process.