145,906 research outputs found
Size dependence of second-order hyperpolarizability of finite periodic chain under Su-Schrieffer-Heeger model
The second hyperpolarizability of
double-bond finite chain of trans-polyactylene is analyzed using the
Su-Schrieffer-Heeger model to explain qualitative features of the
size-dependence behavior of . Our study shows that is
{\it nonmonotonic} with and that the nonmonotonicity is caused by the
dominant contribution of the intraband transition to in polyenes.
Several important physical effects are discussed to reduce quantitative
discrepancies between experimental and our resultsComment: 3 figures, 1 tabl
Deglaciation constraints in the Parâng Mountains, Southern Romania, using surface exposure dating
Cosmogenic nuclide surface exposure ages have been widely used to constrain glacial chronologies in the European regions. This paper brings new evidence that the Romanian Carpathians sheltered mountain glaciers in their upper valleys and cirques until the end of the last glaciation. Twenty-four 10Be surface exposure ages were obtained from boulders on moraine crests in the central area of the Parâng Mountains, Southern Carpathians. Exposure ages were used to constrain the timing of the deglaciation events during the Late Glacial. The lowest boulders yielded an age of 13.0 ± 1.1 (1766 m) and final deglaciation occurred at 10.2 ± 0.9 ka (2055 m). Timing of the Late Glacial events and complete deglaciation reported in this study are consistent with, and confirm, previously reported ages of deglaciation within the Carpathian and surrounding European region
Carrier Dynamics in Submonolayer InGaAs/GaAs Quantum Dots
Carrier dynamics of submonolayer (SML) InGaAs/GaAs quantum dots (QDs) were
studied by micro-photoluminecence (MPL), selectively excited photoluminescence
(SEPL), and time-resolved photoluminescence (TRPL). MPL and SEPL show the
coexistence of localized and delocalized states, and different local phonon
modes. TRPL reveal shorter recombination lifetimes and longer capture times for
the QDs with higher emission energy. This suggests that the smallest SML QDs
are formed by perfectly vertically correlated 2D InAs islands, having the
highest In content and the lowest emission energy, while a slight deviation
from the perfectly vertical correlation produces larger QDs with lower In
content and higher emission energy.Comment: 12 pages, 5 figure
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