144 research outputs found
Explosions of water clusters in intense laser fields
Energetic, highly-charged oxygen ions, (), are copiously
produced upon laser field-induced disassembly of highly-charged water clusters,
and , 60, that are formed by seeding high-pressure
helium or argon with water vapor. clusters (n40000) formed under
similar experimental conditions are found undergo disassembly in the Coulomb
explosion regime, with the energies of ions showing a
dependence. Water clusters, which are argued to be considerably smaller in
size, should also disassemble in the same regime, but the energies of fragment
O ions are found to depend linearly on which, according to
prevailing wisdom, ought to be a signature of hydrodynamic expansion that is
expected of much larger clusters. The implication of these observations on our
understanding of the two cluster explosion regimes, Coulomb explosion and
hydrodynamic expansion, is discussed. Our results indicate that charge state
dependences of ion energy do not constitute an unambiguous experimental
signature of cluster explosion regime.Comment: Submitted to Phys. Rev.
Positronium Hyperfine Splitting in Non-commutative Space at the Order
We obtain positronium Hyperfine Splitting owing to the non-commutativity of
space and show that, in the leading order, it is proportional to where, is the parameter of non-commutativity. It is also
shown that spatial non-commutativity splits the spacing between triplet
excited levels which provides an experimental test on
the non-commutativity of space.Comment: 7 pages, 2 figures, to appear in Phys. Rev.
Experimental Observation of Resonance Effects in Intensely Irradiated Atomic Clusters
We have resolved the expansion of intensely irradiated atomic clusters on a femtosecond time scale. These data show evidence for resonant heating, similar to resonance absorption, in spherical cluster plasmas
Asymmetric emission of high energy electrons in the two-dimensional hydrodynamic expansion of large xenon clusters irradiated by intense laser fields
Energy spectra and angular distributions have been measured of electrons that
are emitted upon disassembly of following irradiation by intense
(10 W cm) laser pulses whose durations are varied over
the 100-2200 fs range. The cluster explosion dynamics occur in the hydrodynamic
regime. Electron emission is found to be unexpectedly asymmetric and exhibits a
resonance when the laser pulse duration is 1 ps. These results are
rationalized by extending the hydrodynamic model to also take into account the
force that the light field exerts on the polarization charge that is induced on
surface of the cluster. We show that the magnitude of this electrostrictive
force is comparable to those of Coulombic and the hydrodynamic forces, and it
exhibits resonance behavior. Contrary to earlier understanding, we find that
low-energy electrons are connected to the resonance in energy absorption by the
cluster. The high-energy electrons seem to be produced by a mechanism that is
not so strongly influenced by the resonance.Comment: 1 Revtex file, 8 figs. in eps forma
Interface Excitons in Krmnen Clusters : The Role of Electron Affinity in the Formation of Electronic Structure
The formation of the electronic structure of small Kr_m clusters (m<150)
embedded inside Ne_N clusters (1200<N<7500) has been investigated with the help
of fluorescence excitation spectroscopy using synchrotron radiation.
Electronically excited states, assigned to excitons at the Ne/Kr interface, 1i
and 1'i were observed. The absorption bands, which are related to the lowest
spin-orbit split atomic Kr 3P1 and 1P1 states, initially appear and shift
towards lower energy when the krypton cluster size m increases. The
characteristic bulk 1t and 1't excitons appear in the spectra, when the cluster
radius exceeds some critical value, R_cl>Delta_1i . Kr clusters comprising up
to 70 atoms do not exhibit bulk absorption bands. We suggest that this is due
to the penetration of the interface excitons into the Kr_m cluster volume,
because of the negative electron affinity of surrounding Ne atoms. From the
energy shift of the interface absorption bands with cluster size an
unexpectedly large penetration depth of delta_1i =7.0+/-0.1 A is estimated,
which can be explained by the interplay between the electron affinities of the
guest and the host cluster
Strong X-Ray Emission from High-Temperature Plasmas Produced by Intense Irradiation of Clusters
Molecular-dynamics simulations in systems of rare gases using Axilrod-Teller and exchange three-atom interactions
Complete Result for Positronium Energy Levels at Order alpha^6 m
We have completed theoretical predictions for positronium energy levels
through order alpha^6 m by the calculation of the spin independent, radiative
recoil correction. This contribution is significant and amounts to 10.64 MHz
for the 1S state. We further perform detailed comparison of theoretical
predictions to experimental results for 1S-2S and 2S-2P transitions.Comment: 9 pages, 2 tables. Email: [email protected]
The comorbidity and co-medication profile of patients with progressive supranuclear palsy
Background: Progressive supranuclear palsy (PSP) is usually diagnosed in elderly. Currently, little is known about comorbidities and the co-medication in these patients. Objectives: To explore the pattern of comorbidities and co-medication in PSP patients according to the known different phenotypes and in comparison with patients without neurodegenerative disease. Methods: Cross-sectional data of PSP and patients without neurodegenerative diseases (non-ND) were collected from three German multicenter observational studies (DescribePSP, ProPSP and DANCER). The prevalence of comorbidities according to WHO ICD-10 classification and the prevalence of drugs administered according to WHO ATC system were analyzed. Potential drug–drug interactions were evaluated using AiDKlinik®. Results: In total, 335 PSP and 275 non-ND patients were included in this analysis. The prevalence of diseases of the circulatory and the nervous system was higher in PSP at first level of ICD-10. Dorsopathies, diabetes mellitus, other nutritional deficiencies and polyneuropathies were more frequent in PSP at second level of ICD-10. In particular, the summed prevalence of cardiovascular and cerebrovascular diseases was higher in PSP patients. More drugs were administered in the PSP group leading to a greater percentage of patients with polypharmacy. Accordingly, the prevalence of potential drug–drug interactions was higher in PSP patients, especially severe and moderate interactions. Conclusions: PSP patients possess a characteristic profile of comorbidities, particularly diabetes and cardiovascular diseases. The eminent burden of comorbidities and resulting polypharmacy should be carefully considered when treating PSP patients
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