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Morphologies of laser-induced damage in hafnia-silica multilayer mirror and polarizer coatings
Hafnium-silica multilayer mirrors and polarizers were deposited by e-beam evaporation onto BK7 glass substrates. The mirrors and polarizers were coated for operation at 1053 nm at 45{degree} and at Brewster`s angle (56{degree}), respectively. They were tested with a single 3-ns laser pulse. Morphology of the laser-induced damage was characterized by optical and scanning electron microscopy. Four distinct damage morphologies were found: pits, flatbottom pits, scalds, and delaminates. The pits and flat bottom pits (<30{mu}m dia) were detected at lower fluences (as low as 5 J/cm{sup 2}). The pits seemed to result from ejection of nodular defects by causing local enhancement of the electric field. Scalds and delaminates could be observed at higher fluences (above 13 J/cm{sup 2}) and seemed to result from the formation of plasmas on the surface. These damage types often originated at pits and were less than 300 {mu}m diameter; their size increased almost linearly with fluence. Finally, effects of the damage on the beam (reflectivity degradation and phase modulations) were measured
Understanding the Random Displacement Model: From Ground-State Properties to Localization
We give a detailed survey of results obtained in the most recent half decade
which led to a deeper understanding of the random displacement model, a model
of a random Schr\"odinger operator which describes the quantum mechanics of an
electron in a structurally disordered medium. These results started by
identifying configurations which characterize minimal energy, then led to
Lifshitz tail bounds on the integrated density of states as well as a Wegner
estimate near the spectral minimum, which ultimately resulted in a proof of
spectral and dynamical localization at low energy for the multi-dimensional
random displacement model.Comment: 31 pages, 7 figures, final version, to appear in Proceedings of
"Spectral Days 2010", Santiago, Chile, September 20-24, 201
Half-life and spin of 60Mn^g
A value of 0.28 +/- 0.02 s has been deduced for the half-life of the ground
state of 60Mn, in sharp contrast to the previously adopted value of 51 +/- 6 s.
Access to the low-spin 60Mn ground state was accomplished via beta decay of the
0+ 60Cr parent nuclide. New, low-energy states in 60Mn have been identified
from beta-delayed gamma-ray spectroscopy. The new, shorter half-life of 60Mn^g
is not suggestive of isospin forbidden beta decay, and new spin and parity
assignments of 1+ and 4+ have been adopted for the ground and isomeric
beta-decaying states, respectively, of 60Mn.Comment: 13 pages, 5 figures, Accepted for publication in Phys. Rev.
Anderson localization for a class of models with a sign-indefinite single-site potential via fractional moment method
A technically convenient signature of Anderson localization is exponential
decay of the fractional moments of the Green function within appropriate energy
ranges. We consider a random Hamiltonian on a lattice whose randomness is
generated by the sign-indefinite single-site potential, which is however
sign-definite at the boundary of its support. For this class of Anderson
operators we establish a finite-volume criterion which implies that above
mentioned the fractional moment decay property holds. This constructive
criterion is satisfied at typical perturbative regimes, e. g. at spectral
boundaries which satisfy 'Lifshitz tail estimates' on the density of states and
for sufficiently strong disorder. We also show how the fractional moment method
facilitates the proof of exponential (spectral) localization for such random
potentials.Comment: 29 pages, 1 figure, to appear in AH
Beta-delayed proton emission in the 100Sn region
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fragments of interest were identified
and their decay was studied with the NSCL Beta Counting System (BCS) in
conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing,
98Inm and 99In were identified as beta-delayed proton emitters, with branching
ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for
89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9
-1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for
101Sn was deduced with higher precision than previously reported. The impact of
the newly measured bp values on the composition of the type-I X-ray burst ashes
was studied.Comment: 15 pages, 14 Figures, 4 Table
The Nandewar Volcano
The Miocene Nandewar Volcano in north-eastern New South Wales is composed of a suite of transitional alkaline eruptives and minor associated intrusives. The volcanics include minor hawaiites but are dominated by a mildly potassic lineage extending from hy-normative trachyandesites to comendites via tristanites and mafic to peralkaline trachytes. Although the trachyandesites, tristanites and trachytes (the main shield-forming sequence) are collectively the most abundant volcanics, alkali rhyolites comprise the most voluminous 'evolved' eruptive type. Peralkaline trachytes and comendites are relatively insignificant volumetrically. Olivine, Ca-rich pyroxene and amphibole display marked decreases in their 100 Mg/(Mg+Fe) ratios in the transition from trachyandesite to comendite, reflecting variation in host-rock compositions. The presence of tschermakitic Ca-rich pyroxenes and aluminian bronzite megacrysts in several trachyandesites indicates that their hosts experienced intratelluric crystallization at elevated pressures (~6 to 8 kb). Some plagioclase, olivine and titanomagnetite phenocrysts may also represent moderate-pressure cognate precipitates. Groundmass pyroxenes in some trachytes and comendites may be strongly acmitic, and this reflects the peralkaline character of those melts. Titanomagnetite is the dominant Fe-Ti oxide phase throughout the series, and only occasionally does it coexist with ilmenite. Fe-Ti oxide compositional data indicate that magmas spanning the spectrum trachyandesite to comendite generally crystallized under conditions of decreasing T and Ć’oâ‚‚ which were broadly parallel with the FMQ synthetic buffer curve. However, some alkali rhyolites appear to have crystallized under significantly more oxidizing conditions. Crystallization of aenigmatite in the groundmass of peralkaline trachytes and comendites also reflects relatively strongly reducing conditions in the more 'evolved' variants and ns-bearing melts. In several specimens the presence of aenigmatite rimming titanomagnetite and ilmenite microphenocrysts provides some support for the existence of a 'no-oxide' field in T-Ć’oâ‚‚ space
Evidence for a change in the nuclear mass surface with the discovery of the most neutron-rich nuclei with 17<Z <25
The results of measurements of the production of neutron-rich nuclei by the
fragmentation of a 76-Ge beam are presented. The cross sections were measured
for a large range of nuclei including fifteen new isotopes that are the most
neutron-rich nuclides of the elements chlorine to manganese (50-Cl, 53-Ar,
55,56-K, 57,58-Ca, 59,60,61-Sc, 62,63-Ti, 65,66-V, 68-Cr, 70-Mn). The enhanced
cross sections of several new nuclei relative to a simple thermal evaporation
framework, previously shown to describe similar production cross sections,
indicates that nuclei in the region around 62-Ti might be more stable than
predicted by current mass models and could be an indication of a new island of
inversion similar to that centered on 31-Na.Comment: 4 pages, 3 figures, to be published in Physical Review Letters, 200
Low lying spectrum of weak-disorder quantum waveguides
We study the low-lying spectrum of the Dirichlet Laplace operator on a
randomly wiggled strip. More precisely, our results are formulated in terms of
the eigenvalues of finite segment approximations of the infinite waveguide.
Under appropriate weak-disorder assumptions we obtain deterministic and
probabilistic bounds on the position of the lowest eigenvalue. A Combes-Thomas
argument allows us to obtain so-called 'initial length scale decay estimates'
at they are used in the proof of spectral localization using the multiscale
analysis.Comment: Accepted for publication in Journal of Statistical Physics
http://www.springerlink.com/content/0022-471
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