Radiative Auger process in the single-photon limit

In a multi-electron atom, an excited electron can decay by emitting a photon. Typically, the leftover electrons are in their ground state. In a radiative Auger process, the leftover electrons are in an excited state and a redshifted photon is created. In a semiconductor quantum dot, radiative Auger is predicted for charged excitons. Here we report the observation of radiative Auger on trions in single quantum dots. For a trion, a photon is created on electron-hole recombination, leaving behind a single electron. The radiative Auger process promotes this additional (Auger) electron to a higher shell of the quantum dot. We show that the radiative Auger effect is a powerful probe of this single electron: the energy separations between the resonance fluorescence and the radiative Auger emission directly measure the single-particle splittings of the electronic states in the quantum dot with high precision. In semiconductors, these single-particle splittings are otherwise hard to access by optical means as particles are excited typically in pairs, as excitons. After the radiative Auger emission, the Auger carrier relaxes back to the lowest shell. Going beyond the original theoretical proposals, we show how applying quantum optics techniques to the radiative Auger photons gives access to the single-electron dynamics, notably relaxation and tunneling. This is also hard to access by optical means: even for quasi-resonant $p$-shell excitation, electron relaxation takes place in the presence of a hole, complicating the relaxation dynamics. The radiative Auger effect can be exploited in other semiconductor nanostructures and quantum emitters in the solid state to determine the energy levels and the dynamics of a single carrier

Effect sizes of non-surgical treatments of non-specific low-back pain.

Numerous randomized trials have been published investigating the effectiveness of treatments for non-specific low-back pain (LBP) either by trials comparing interventions with a no-treatment group or comparing different interventions. In trials comparing two interventions, often no differences are found and it raises questions about the basic benefit of each treatment. To estimate the effect sizes of treatments for non-specific LBP compared to no-treatment comparison groups, we searched for randomized controlled trials from systematic reviews of treatment of non-specific LBP in the latest issue of the Cochrane Library, issue 2, 2005 and available databases until December 2005. Extracted data were effect sizes estimated as Standardized Mean Differences (SMD) and Relative Risk (RR) or data enabling calculation of effect sizes. For acute LBP, the effect size of non-steroidal anti-inflammatory drugs (NSAIDs) and manipulation were only modest (ES: 0.51 and 0.40, respectively) and there was no effect of exercise (ES: 0.07). For chronic LBP, acupuncture, behavioral therapy, exercise therapy, and NSAIDs had the largest effect sizes (SMD: 0.61, 0.57, and 0.52, and RR: 0.61, respectively), all with only a modest effect. Transcutaneous electric nerve stimulation and manipulation had small effect sizes (SMD: 0.22 and 0.35, respectively). As a conclusion, the effect of treatments for LBP is only small to moderate. Therefore, there is a dire need for developing more effective interventions. © 2007 Springer-Verlag

Single-molecule Magnets on Surfaces

Encoding and manipulating information through the spin degrees of freedom of individual magnetic molecules or atoms is one of the central challenges in the continuing trend towards molecular/atomic scale electronics. With their large magnetic moment and long spin relaxation time, single-molecule magnets (SMMs) are of special importance in this emerging field. Their electrical addressing at the molecular level appears now well within reach using STM methods, which require to organize SMMs on a conducting surface. In this chapter, we present a critical overview of the latest achievements in the deposition of SMMs as monolayers or submonolayers on native or prefunctionalized surfaces. Special emphasis is placed on the selection and design of molecular structures that withstand solution or vapour-phase processing and that maintain their magnetic functionality on a surface. Chemical strategies to control the strength of molecule\u2013substrate interaction and the molecular orientation on the surface are also illustrated. Rewardingly, these efforts have shown that the distinctive properties of SMMs, i.e. slow spin relaxation and quantum tunnelling of the magnetic moment, persist in metal-wired molecules

Magnetic Surfaces, Thin Films and Nanostructures

Kinetics and Thermodynamics at Surfaces -- Surface Crystallography -- Electronic Structure of Surfaces -- Collective and Single Particle Excitations. - Surface Magnetism -- Lattice Dynamics -- Gas Surface Interaction. - Chemical Reactions at Surfaces -- Current topics in surface scienc