Scanning tunnelling spectroscopy of electron resonators

The electronic structure of artificial Mn atom arrays on Ag(111) is characterized in detail with scanning tunnelling spectroscopy and spectroscopic imaging at low temperature. We demonstrate the degree to which variations in geometry may be used to control spatial and spectral distributions of surface state electrons confined within the arrays, how these are influenced by atoms placed within the structure and how the ability to induce spectral features at specific energies may be exploited through lineshape analyses to deduce quasiparticle lifetimes near the Fermi level. Through extensive comparison of $dI/dV$ maps and spectra we demonstrate the utility of a model based upon two-dimensional s-wave scatterers for describing and predicting the characteristics of specific resonators

Photon Emission Induced by the Scanning Tunneling Microscope

By using the tip of a scanning tunneling microscope (STM) as a local source for electrons (or holes) light emission can be excited from metals, semiconductors and molecules. Using this technique, it is possible to combine the high spatial resolution of STM with optical techniques. We review results obtained using a variety of modes of measurements including fluorescence spectroscopy, isochromat spectroscopy and simultaneous mapping of photon emission and surface topography. In spatial maps of the photon emission, clear contrasts are observed with lateral resolutions below 1 nm which are related to the geometric and electronic structure of the sample and the tip. In particular, recent results on atomic resolution of Au(110) are discussed to highlight the important role of the electromagnetic interaction of the tip and the sample for the observed photon emission

Ultraviolet light emission from Si in a scanning tunneling microscope

Ultraviolet and visible radiation is observed from the contacts of a scanning tunneling microscope with Si(100) and (111) wafers. This luminescence relies on the presence of hot electrons in silicon, which are supplied, at positive bias on n- and p-type samples, through the injection from the tip, or, at negative bias on p-samples, by Zener tunneling. Measured spectra reveal a contribution of direct optical transitions in Si bulk. The necessary holes well below the valence band edge are injected from the tip or generated by Auger processes

Price Indexes for Acute Phase Treatment of Depression

Although broad trends in medical spending in the U.S. over the last decade have received widespread attention from policymakers, very little attention has focused on the components of those changes. For many other industries, economists typically divide nominal expenditures by an official government price index to decompose these expenditures into price and quantity components. In this paper we construct a new price index for the treatment of one illness depression. Making use of results from the published clinical literature and from official treatment guideline standards, we identify therapeutically similar treatment bundles. These bundles can then be linked and weighted to construct price indexes for specific forms of major depression. In doing so, we construct CPI and PPI-like medical price indexes that deal with prices of treatment episodes rather than prices of discrete inputs, that are based on transaction rather than list prices, that take quality changes and expected outcomes into account employ current, time-varying expenditure weights in the aggregation computations. We find that regardless of which index number procedure is employed time period the treatment price index for the acute phase of major depression has hardly changed remaining at 1.00 or falling slightly to around 0.97. This index grows considerably less rapidly than the various official PPIs -- thus the price index for the treatment of the acute phase of major depression has fallen over the 1991-95 time period. A hedonic approach to price index measurement yields broadly similar results. These results imply that given a budget for treatment of depression accomplished in 1995 than in 1991. Our results suggest that at least in the case of acute phase major depression, aggregate spending increases are due to a larger number of effective treatments being provided.

Early Retirement and Public Disability Insurance Applications: Exploring the Impact of Depression

This paper investigates the impact of depression on labor force participation among older workers. Empirically, we use two analytic strategies and rely on a sample drawn from the Health and Retirement Survey. Depression directly and indirectly increases individuals%u2019 probability of retiring early and applying for DI benefits, after accounting for other predictors of labor force exit. Accounting for the independent effects of depression, disability associated with physical illness may be smaller than the official statistics suggest. There may be great economic gains in increasing depression treatment awareness and access to treatment for individuals, employers and society.

Two-Electron Photon Emission From Metallic Quantum Wells

Unusual emission of visible light is observed in scanning tunneling microscopy of the quantum well system Na on Cu(111). Photons are emitted at energies exceeding the energy of the tunneling electrons. Model calculations of two-electron processes which lead to quantum well transitions reproduce the experimental fluorescence spectra, the quantum yield, and the power-law variation of the intensity with the excitation current.Comment: revised version, as published; 4 pages, 3 figure

Real Output in Mental Health Care During the 1990s

Health accounts document changes over time in the level and composition of health spending. There has been a continued evolution in the ability to track such outlays. Less rapid has been the ability to interpret changes in spending. In this paper we apply quality adjusted price indexes for several major mental disorders to national mental health account estimates to assess changes in real "output". We show that using the new price indexes reveals large gains in real output relative to application of BLS indexes.