23 research outputs found
Analytical solution of the radiative transfer equation in the two-stream approximation
Ultrafast charge transfer processes accompanying KLL Auger decay in aqueous KCl solution
X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl
solution were measured for the K and Cl edges. While the XPS spectra of
potassium and chloride have similar structures, both exhibiting only weak
satellite structures near the main line, the Auger spectra of these
isoelectronic ions differ dramatically. A very strong satellite peak was found
in the K KLL Auger spectrum at the low kinetic energy side of the D
state. Using equivalent core models and ab initio calculations this spectral
structure was assigned to electron transfer processes from solvent water
molecules to the solvated K cation. Contrary to the potassium case, no
extra peak was found in the KLL Auger spectrum of solvated Cl indicating on
a strong dependence of the underlying processes on ionic charge. The observed
charge transfer processes are suggested to play an important role in charge
redistribution following single and multiple core-hole creation in atomic and
molecular systems placed into an environment
Enhanced Ionization of Embedded Clusters by Electron-Transfer-Mediated Decay in Helium Nanodroplets
We report the observation of electron-transfer-mediated decay (ETMD) involving magnesium (Mg) clusters embedded in helium (He) nanodroplets. ETMD is initiated by the ionization of He followed by removal of two electrons from the Mg clusters of which one is transferred to the He ion while the other electron is emitted into the continuum. The process is shown to be the dominant ionization mechanism for embedded clusters for photon energies above the ionization potential of He. For Mg clusters larger than five atoms we observe stable doubly ionized clusters. Thus, ETMD provides an efficient pathway to the formation of doubly ionized cold species in doped nanodroplets
Observation of electron transfer mediated decay in aqueous solution
Photoionization is at the heart of X ray photoelectron spectroscopy XPS , which gives access to important information on a sample s local chemical environment. Local and non local electronic decay after photoionization in which the refilling of core holes results in electron emission from either the initially ionized species or a neighbour, respectively have been well studied. However, electron transfer mediated decay ETMD , which involves the refilling of a core hole by an electron from a neighbouring species, has not yet been observed in condensed phase. Here we report the experimental observation of ETMD in an aqueous LiCl solution by detecting characteristic secondary low energy electrons using liquid microjet soft XPS. Experimental results are interpreted using molecular dynamics and high level ab initio calculations. We show that both solvent molecules and counterions participate in the ETMD processes, and different ion associations have distinctive spectral fingerprints. Furthermore, ETMD spectra are sensitive to coordination numbers, ion solvent distances and solvent arrangemen
Analytical solution of the radiative transfer equation in the two-stream approximation
The analytical solution of the plane-parallel radiative transfer equation is
obtained in the two-stream approximation for a large class of continuous
distributions of the de-excitation coefficient ε (constant, linear,
parabolic, with spikes etc.).
We present also the method of the discrete space theory for obtaining
solutions of the transfer equation in the media with strong density
inhomogeneities.
These sets of the analytical solutions can be used for the solution of the
inverse problem. The deduction of the internal distribution of
ε from observational data is facilitated in the case
of isothermal media, since the characteristic behavior of the solution
refers to the certain behavior of ε. As an example, we find
the corresponding parameters of the constant and linear distributions of
ε precisely
Inner-shell single and double ionization potentials of aminophenol isomers
A comprehensive study of single and double core ionization potentials of the aminophenol molecule is reported. The role of relaxation, correlation, relativistic, and basis set effects in these potentials is clarified. Special attention is paid to the isomer dependence of the single and double core ionization potentials. Some of them are also compared with the respective values of the phenol and aniline molecules. It is shown that the core level single ionization potentials of the para-, meta-, and ortho-aminophenol molecules differ only slightly from each other, rendering these structural isomers challenging to distinguish for conventional x-ray photoelectron spectroscopy. In contrast, the energy needed to remove two core electrons from different atoms depends noticeably on the mutual arrangement and even on the relative orientations of the hydroxyl and amine groups. Together with the electrostatic repulsion between the two core holes, relaxation effects accompanying double core ionization play a crucial role here. The pronounced sensitivity of the double ionization potentials, therefore, enables a spectroscopic characterization of the electronic structure of aminophenol isomers by means of x-ray two-photon photoelectron spectroscopy