Determination of surface electronic states of solids in solution by means of charge transfer reaction inverse photoemission spectroscopy (CTRIPS).

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The details of the photon emission at metal/electrolyte interfaces induced by an electron transfer reaction was investigated by employing two experimental procedures.In the first method, the measurements were carried out in solutions containing some redox species. The potential was stepped to a negative potential, U_i. where the redox species is converted to as anion radical, and then to various positive potentials, U_f, where the anion radical is oxidized. The effects of electrode metals (Au, Pt and Pd) and redox species (benzonitrile. tstilbene and benzophenone) on emission properties were studied. The high energy threshold of the spectrum, E_<th>, changes linearly with the electrode potential, U_f, and is almost equal to -e (Uﾟ-U_f) where Uﾟis the redox potential of the chemical species. The peak position of the spectrum, E_p, also depends though less sensitively on U_f and Uﾟ. Although E_<th> is solely determined by U_f and Uﾟ, E_p has metal dependence. Emission efficiency. PHI, in … More creases, saturates and then decreases as U_f becomes more positive. The potential dependence of PHI also depends on the choice of metal. Based on these results, several possible mechanisms for the photon emission are considered and it is concluded that the major contribution to the photon emission is the charge transfer reaction inverse photoemission (CTRIP) process involving bulk band states.In the second method, solvated electrons were used as electron injecting spesies and the electrode potential was kept constant. The efficiency of emitted light increases drastically as the electrode potential becomes positive. The high energy threshold of the spectrum also increases as the electrode potential becomes positive by 1 eV/V. The peak energy also shifts positively as the electrode potential becomes positive, although the degree of the shift is much smaller. Various processes are considered as a possible mechanism for a photon emission. From the qualitative comparison of the results at plantinum and gold electrode, the contribution of the inverse photoemission process to thebulk band states at the light emission process in the electrochemical system is suggested. The feasibility of applying this phenomenon to a novel spectroscopy is discussed. Information on electronic states of solvated electrons was also obtained. Less