(a) Yield functions of 16O− desorption from a self-assembled monolayer of DNA (SAM-DNA) and SAM-DNA dosed with an additional ∼0.75 ML (equivalent) of 16O2 at each indicated temperature. (b) Yield functions of OH− desorption recorded under the same conditions as in (a). (c) Details of resonance structure seen in the O− yield functions recorded at 165 K. The experimental data obtained by adding O2 (squares) can be reproduced (dashed line) by adding a scaled version of the data obtained at 55 K (dotted line) to the signal recorded for the pure SAM-DNA. The vertical arrow denotes the energy of the 2Πu state O2 −.
Time variation of energy-integrated (a) 18O− and (b) 18OH− desorption yields from a SAM-DNA sample as it is cooled to 50 K, dosed repeatedly with 18O2, and then heated to 250 K. The Y-axis represents the result of integrating anion yield functions over the range 2–18 eV.
Anion yield functions for a) 18O− and b) 18OH− from SAM-DNA measured at 150 K after dosing with 3.5 ML of 18O2 at 50 K. Yield functions were obtained with an incident current of ∼2 nA, an energy step-size of 0.5 eV and 50,000 electrons pulses per point. The SAM-DNA films were irradiated with 0-18 eV electrons (at an incident current of 2 nA) for the indicated periods prior to their exposure to 18O2.
Variation of the energy integrated yields of a) 18O− and b) 18OH− data of Fig. 3 with period of electron pre-irradiation (0 eV < E i< 18 eV) prior to exposure to 18O2.
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