Dear Joker,

Perform XPS of pure Sn(II) and Sn(II)-complex. Then observe the change in Binding energy (BE) of Sn(II) from control sample to the complex. A decrease in BE suggests the enhancement of electronic density on Sn(II). This will provide you some useful information regarding the electron affinity of Sn(II).

Thank you.

Electron affinity is a measure of the energy given up in the reduction reaction of the neutral species or ion with an electron. The two techniques you mention, UPS and XPS, are photoemission. Electrons leave the orbitals, they do not enter them. To complete the association of photoemission binding energy with electron affinity, consider the relationship from a Born-Haber cycle approach.

All else being the same, photoelectrons leaving from n+ or n- oxidation states are ... photoelectrons leaving from n+ or n- oxidation states. Whether that oxidation state is induced by oxygen or a molecular ligand matters not. Therefore, the photoemission binding energy will not change due to the ligand. What does change is how the hole that is created during the photoemission process relaxes back to a ground state. Higher electron densities around the hole (e.g. greater free electron density) will decrease relaxation times. The effect is apparent when spectra of gas phase molecules are compared with those from condensed phases. Additional peaks (loss peaks) appear or not, and the main photoemission peaks may shift position (final state effects).

To first order, the quantitative result that you can obtain in XPS is the relative amounts of various oxide states in the material. Consider this as a measure of the yield or efficiency of your stabilization reaction to the various pathways to form each oxidation state.

The information you can obtain from UPS is a density of states at the valence band. Consider this as input to a theoretical calculation of HOMO/LUMO structures and molecular density of states maps.

Tin is a typical element which does not show the XPS chemical shift. If you check any data book on XPS, you can find both SnO and SnO2 3d5/2 peak is around 486.5 eV. Their nominal oxidation numbers are Sn2+ and Sn4+, but the peak energy is almost identical. This is very strange. I have had a question why they are almost the same binding energy? Lead (Pb) is similar. I think someone has already solved this problem, but I do not know. In order to know the electron affinity of organic Sn2+ compounds by XPS, one must know the reason of the strange behavior of tin before that.

I hope someone will answer also to my question.

To Tun: The Kinetik energy of the outgoing electron is not only determinier by the chemical shift but in addition also by the relaxation energy associated with the remaining core hole. In the end it might happen that both contributions cancel out. see e.g. Ag or Cu metal and +1 state.

Dear Cheistian

The reason that the CuO and Cu2O 2p XPS binding energies are almost identical is that the strongest peak of CuO Cu 2p3/2 is due to the well-screened state, i.e. the dynamical charge transfer state (3d10) of CuO due to the creation of core hoe. Cu2O ground state is 3d10. The chemical shift between CuO and Cu2O is the energy difference between 2p3/2 so-called shake-up satellite (but this peak is in fact 3d9 poorly screened state) and Cu2O 2p3/2 (3d10) peaks. This is the case of transition metal compounds. Please check my old paper, Phys. Rev. Lett., 65, 2193-2196 (1990) and references therein (this is not an XPS but Ni X-ray emission spectra).

But for typical elements such as Sn, I do not know such rationalization. I hope someone will answer.

Yours sincerely

Jun

Dear Jun I was talking of Cu and Ag metal compared to Cu1+ and Ag1+ which show almost similar bindig energies. for Cu2+ it is completely different as it is obvious from the spectra and your explanation. I tried only to mention that chemical shift and relaxation may cancel out.

Dear Cheistian

Thank you for Recommending my answer. We must returning to the Sn XPS. We have still a fundamental open problem even for Sn XPS.

The question of Effat Jokar is a very important fundamental question.

then with XPS is not possible to find out the reason of stability of tin when was compelexed by special organic cation. which method do you recommend me to analyse this phenomena. thanks for all of your past comments.

Dear Jokar,

In my humble opinion here, in attached papers one can see the good version of explanation why sometimes Sn2+ and Sn4+ charge states are very hard to distinguish.

Nevertheless, having extra good XPS resolution it is possible.

Please look attached papers and especially table in attached J. Electrochem.

Prof. J.Kawai-san gave good explanations and I wish only to add these some papers for better recognizing.

Hope it will be useful.

Regards,

Dmitry

....also please look here (paper is attached) - as well good proved explanation based on Madelung for the small difference of Sn2+ and Sn4+.

Kindest wishes,

Dmitry

According to Cu 2p satellites.

I think that these pioneering manuscripts in XPS after Japanese researches should not be ignored.

Their XPS data is VERY important in my humble opinion and actually

well explained, even visually (especially in PNG picture).

Regards,

Dmitry

Thank you