Swift heavy ions on polymers: Hydrocarbon gas release

In order to understand how bond cleavages occur during ion-polymer interact ion, we have made quantitative measurements of the gases evolved under irra diation from the polymers polyethylene, polypropylene and polybutene. The i ons used for irradiation were 10.2 MeV amu(-1) C-13, 2.6 MeV amu(-1) N-14 a nd 6 MeV amu(-1) Ni-58. We conceived a new set-up using a Fourier Transform Infrared analysis of the gas mixture released from the polymer film. Obser vation of the recorded spectra clearly shows that molecular emission is ext remely sensitive to the electronic stopping power (dE/dx)(e). At low (dE/dx )(e), gas yields are strongly polymer dependent and we mainly observe the s cission of the tertiary bond: Polypropylene (PP) releases methane and Polyb utene (PB) ethane. At high (dE/dx)(e), we observe principally acetylene emi ssion, other unsaturated molecules are also greatly favoured. Gas yields ar e therefore less specific of a given polymer. We show in this work, that th e chemical identification of the molecules outgassing the polymer him expla ins how a polymer chain reacts towards clustered ionisation induced by swif t heavy ions. (C) 1998 Elsevier Science B.V. All rights reserved.