Photon stimulated ion desorption from poly(3-methylthiophene) following sulphur K-shell excitation

Photon stimulated ion desorption (PSID) studies have been performed in poly(3-methylthiophene) (PMeT) using synchrotron radiation at the sulphur 1s-edge. The PSID studies were performed at the Brazilian Synchrotron Light Source (LNLS), operating in a single-bunch mode. It was found that S 1s→π∗, σ∗ (S–C) and higher energy excitations produce S+ desorption with a partial ion yield curve similar to the photoabsorption spectrum. On the other hand, S2+ desorption is enhanced at higher energy excitations. These results are interpreted solely in terms of the Auger-stimulated ion desorption mechanism, since no S+ or S2+ desorption was observed outside the sulphur 1s-edge. In addition, desorption of H+ and other minor fragments of PMeT desorb mainly by XESD (X-ray induced electron stimulated desorption). To our knowledge, it is the first observation of multiple charged ions in PSID studies of polymers.