536 research outputs found
29Si Hyperfine Structure of the E'_\alpha Center in Amorphous Silicon Dioxide
We report a study by electron paramagnetic resonance (EPR) on the E'_\alpha
point defect in amorphous silicon dioxide (a-SiO2). Our experiments were
performed on gamma-ray irradiated oxygen-deficient materials and pointed out
that the 29Si hyperfine structure of the E'_alpha consists in a pair of lines
split by 49 mT. On the basis of the experimental results a microscopic model is
proposed for the E'_alpha center, consisting in a hole trapped in an oxygen
vacancy with the unpaired electron sp3 orbital pointing away from the vacancy
in a back-projected configuration and interacting with an extra oxygen atom of
the a-SiO2 matrix.Comment: 4 page
Opto-Electrical Cooling of Polar Molecules
We present an opto-electrical cooling scheme for polar molecules based on a
Sisyphus-type cooling cycle in suitably tailored electric trapping fields.
Dissipation is provided by spontaneous vibrational decay in a closed level
scheme found in symmetric-top rotors comprising six low-field-seeking
rovibrational states. A generic trap design is presented. Suitable molecules
are identified with vibrational decay rates on the order of 100Hz. A simulation
of the cooling process shows that the molecular temperature can be reduced from
1K to 1mK in approximately 10s. The molecules remain electrically trapped
during this time, indicating that the ultracold regime can be reached in an
experimentally feasible scheme
Probing the Structure, Pseudorotation, and Radial Vibrations of Cyclopentane by Femtosecond Rotational Raman Coherence Spectroscopy
On Quantum State Observability and Measurement
We consider the problem of determining the state of a quantum system given
one or more readings of the expectation value of an observable. The system is
assumed to be a finite dimensional quantum control system for which we can
influence the dynamics by generating all the unitary evolutions in a Lie group.
We investigate to what extent, by an appropriate sequence of evolutions and
measurements, we can obtain information on the initial state of the system. We
present a system theoretic viewpoint of this problem in that we study the {\it
observability} of the system. In this context, we characterize the equivalence
classes of indistinguishable states and propose algorithms for state
identification
Conditional Coverage and Its Role in Determining and Assessing Long-Term Capital Requirements
The Role of Industry, Geography and Firm Heterogeneity in Credit Risk Diversification
In theory the potential for credit risk diversification for banks could be substantial. Portfolio diversification is driven broadly by two characteristics: the degree to which systematic risk factors are correlated with each other and the degree of dependence individual firms have to the different types of risk factors. We propose a model for exploring these dimensions of credit risk diversification: across industry sectors and across different countries or regions. We find that full firm-level parameter heterogeneity matters a great deal for capturing differences in simulated credit loss distributions. Imposing homogeneity results in overly skewed and fat-tailed loss distributions. These differences become more pronounced in the presence of systematic risk factor shocks: increased parameter heterogeneity greatly reduces shock sensitivity. Allowing for regional parameter heterogeneity seems to better approximate the loss distributions generated by the fully heterogeneous model than allowing just for industry heterogeneity. The regional model also exhibits less shock sensitivity
Basel II and fostering the disclosure of banks\' internal credit ratings
ISSN:1566-7529ISSN:1741-620
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