Free silver nanoparticles doped by potassium:work-function change in experiment and theory

Abstract The composition-dependent change in the work-function (WF) of binary silver–potassium nanoparticles has been studied experimentally by synchrotron-based x-ray photoelectron spectroscopy (PES) and theoretically using a microscopic jellium model of metals. The Ag–K particles with different K fractions were produced by letting a beam of preformed Ag particles pass through a volume with K vapor. The PES on a beam of individual non-supported Ag–K nanoparticles created in this way allowed a direct absolute measurement of their WF, avoiding several usual shortcomings of the method. Experimentally, the WF has been found to be very sensitive to K concentration: Already at low exposure, it decreased down to ≈2 eV—below the value of pure K. In the jellium modeling, considered for Ag–K nanoparticles, two principally different adsorption patterns were tested: without and with K diffusion. The experimental and calculation results together suggest that only efficient surface alloying of two metals, whose immiscibility was long-term textbook knowledge, could lead to the observed WF values

Deep core photoionization of iodine in CH₃I and CF₃I molecules:how deep down does the chemical shift reach?

Abstract Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH₃I) and trifluoroiodomethane (CF₃I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms

Initial-state-selected MNN Auger spectroscopy of atomic rubidium

Abstract The M4,5N2,3N2,3 and M4,5N1N2,3 Auger decay of atomic Rb have been studied by using photoelectron-Auger electron coincidence measurements that enable initial ionic state selected Auger spectroscopy. The Auger spectra in the present study are separated by the total angular momentum j of the 3d hole and the orbital of the valence electron nℓ after photoionization. It is shown that the technique allows isolating overlapping features and the study of otherwise unobservable spectral details, from which the presence of shake-down transitions during normal Auger decay is demonstrated experimentally. The technique allows also probing the effects of initial state parity and electron correlation in Auger electron spectroscopy. The observed spectral features are interpreted with theoretical predictions obtained from configuration interaction Dirac-Fock approach

Probing RbBr solvation in freestanding sub-2nm water clusters

Abstract Concentration dependent solvation of RbBr in freestanding sub-2 nm water clusters was studied using core level photoelectron spectroscopy with synchrotron radiation. Spectral features recorded from dilute to saturated clusters indicate that either solvent shared or contact ion pairs are present in increasing amount when the concentration exceeds 2 mol kg−1. For comparison, spectra from anhydrous RbBr clusters are also presented

Search for the interatomic Auger effect in nitrous oxide

Abstract The interatomic Auger effect following O 1s ionization in N₂O has been experimentally investigated using multi-electron coincidence spectroscopy. The expected transition energies have been established by comparison to the measured N 1s⁻¹v⁻¹ core-valence double ionization energies. We describe a procedure to eliminate the background of two competing processes contributing spectroscopic signatures to the same energy range, namely double Auger decay of the O 1s vacancy and direct single-photon double ionization into the N 1s⁻¹v⁻¹ states. While the interatomic Auger transitions could not be successfully isolated, we provide an upper boundary of the transition probability of 0.07% with respect to the dominant single Auger decay after O 1s ionization

Electron spectroscopy and dynamics of HBr around the Br 1s⁻¹ threshold

Abstract A comprehensive electron spectroscopic study combined with partial electron yield measurements around the Br 1s ionization threshold of HBr at ≅13.482 keV is reported. In detail, the Br 1s⁻¹ X-ray absorption spectrum, the 1s⁻¹ photoelectron spectrum as well as the normal and resonant KLL Auger spectra are presented. Moreover, the L-shell Auger spectra measured with photon energies below and above the Br 1s⁻¹ ionization energy as well as on top of the Br 1s⁻¹σ* resonance are shown. The latter two Auger spectra represent the second step of the decay cascade subsequent to producing a Br 1s⁻¹ core hole. The measurements provide information on the electron and nuclear dynamics of deep core-excited states of HBr on the femtosecond timescale. From the different spectra the lifetime broadening of the Br 1s⁻¹ single core-hole state as well as of the Br(2s⁻²,2s⁻¹2p⁻¹,2p⁻²) double core-hole states are extracted and discussed. The slope of the strongly dissociative HBr 2p⁻²σ* potential energy curve is found to be about −13.60 eV Å⁻¹. The interpretation of the experimental data, and in particular the assignment of the spectral features in the KLL and L-shell Auger spectra, is supported by relativistic calculations for HBr molecule and atomic Br