116 research outputs found
Topological Pressure-Temperature State Diagram of the Crystalline Dimorphism of 2,4,6-trinitrotoluene
International audienc
Detailed analysis of shake structures in the KLL Auger spectrum of H2S
Shake processes of different origin are identified in the KLL Auger spectrum
of H2S with unprecedented detail. The KLL Auger spectrum is presented together
with the S 1sâ1 photoelectron spectrum including the S 1sâ1Vâ1nλ and S
1sâ12pâ1nλ shake-up satellites with Vâ1 and nλ indicating a hole in the
valence shell and an unoccupied molecular orbital, respectively. By using
different photon energies between 2476 and 4150 eV to record the KLL Auger
spectra two different shake-up processes responsible for the satellite lines
are identified. The first process is a shake-up during the Auger decay of the
S 1sâ1 core hole and can be described by S 1sâ1â2pâ2Vâ1nλ. The second process
is the Auger decay of the shake-up satellite in the ionization process leading
to S 1sâ1Vâ1nλâ2pâ2Vâ1nλ transitions. By combining the results of
photoelectron and Auger spectra the involved Vâ1nλ levels are assigned
Experimental And Topological Determination of the Pressure-Temperature Phase Diagram of Racemic Etifoxine, a Pharmaceutical Ingredient with Anxyolitic Properties
International audienc
Postcollision interaction effects in KLL Auger spectra following argon 1s photoionization
Postcollision interaction effects on the Auger decay of a deep core hole are
studied both experimentally and theoretically. KL2,3L2,3 decay spectra of the
Ar 1s vacancy are measured with high-energy resolution with excess photon
energies ranging from 0 to 200 eV above the ionization threshold. Interaction
of the Auger electron with the photoelectron and the ion field manifests
itself in the Auger spectra as a distortion of the energy distribution of the
Auger electron close to threshold. Moreover, recapture of the photoelectron
due to energy exchange is dominating in the low-photon-energy range above
threshold. The experimental results are compared with calculations based on
the semiclassical approach to the postcollision interaction. The energies of
the discrete levels and individual recapture cross sections are computed in
the Hartree-Fock approximation. Good agreement is found between the calculated
and experimental spectra, validating the model used
Two-to-one Auger decay of a double L vacancy in argon
We have observed L223âM3 Auger decay in argon where a double vacancy is filled
by two valence electrons and a single electron is ejected from the atom. A
well-resolved spectrum of these two-to-one electron transitions is compared to
the result of the second-order perturbation theory and its decay branching
ratio is determined
Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy
We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O Kâ2 threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water. Furthermore, we have identified symmetric and antisymmetric dissociation modes characteristic for particular DCH states. Our results serve as a fundamental reference for state-of-the-art studies of DCH dynamic processes in liquid water both at synchrotron and free-electron-laser facilities
Auger resonant-Raman decay after Xe L-edge photoexcitation
We have investigated resonant Auger decay of xenon following photoexcitation
of each of the three L edges under resonant-Raman conditions, which allowed us
to characterize several higher Rydberg transitions. Relative intensities for
spectator final states reached after L1â, L2â, and L3-edge excitations are
studied in detail. Thanks to state-of-the-art experimental arrangements, our
results not only reproduce the previously calculated 3dâ25d and nd(n>5) state
cross sections after L3 excitation, but also allow extracting the 3dâ26d
spectator state energy position and revealing its resonant behavior, blurred
by the insufficient experimental resolution in previous data sets. The 3dâ26p
and 3dâ27p states reached after L1 excitation as well as the 3dâ25d and 3dâ26d
states reached after L2 excitation are also investigated and their relative
intensities are reported and compared to ab initio Dirac-Hartree-Fock
configuration-interaction calculations. We found the signature of electronic-
state-lifetime interference effects between several coherently excited
intermediate states, due to large lifetime broadening. Electron recapture
processes are also identified above all three photoionization thresholds
Argon as a showcase
Electronic-stateâlifetime interference is a phenomenon specific for ionization
of atoms and molecules in the hard-x-ray regime. Using resonant KL2,3L2,3
Auger decay in argon as a showcase, we present a model that allows extracting
the interference terms directly from the cross sections of the final
electronic states. The analysis provides fundamental information on the
excitation and decay processes such as probabilities of various decay paths
and the values of the dipole matrix elements for transitions to the excited
states. Our results shed light on the interplay between spectator, shake-down,
and shake-up processes in the relaxation of deep core-hole states
Direct Observation of Double-Core-Hole Shake-Up States in Photoemission
Direct measurements of Ar+ 1sâ12pâ1nl double-core-hole shake-up states are
reported using conventional single-channel photoemission, offering a new and
relatively easy means to study such species. The high-quality results yield
accurate energies and lifetimes of the double-core-hole states. Their
photoemission spectrum also can be likened to 1s absorption of an exotic argon
ion with a 2p core vacancy, providing new information about the spectroscopy
of both this unusual ionic state as well as the neutral atom
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