Experimental photoresponses and electrical characteristics of metal/P-FeSi,/Si structures are presented. Three kinds of samples are compared: two with a thin epitaxial silicide layer (180A), preparedby two different methods, and one with a thick polycrystalline silicide layer (2500 A). The rectifying behaviour and the photoelectric response of the three kinds of samples are different. In the thin samples these properties are governed by those of the P-FeSi,/Si interface, whereas for thick samples bulk mechanisms dominate. Analysis of the photocurrent in one kind of thin sample shows that two contributions exist. Their intensities follow similar temperature behaviours but the two transition thresholds do not. These considerations allow assignment of the initial and final states of the transitions, and the upper threshold is shown to correspond to an internal photoemission effect at the P-FeSi,/Si interface. The conduction band offset is deduced from the difference between the two thresholds The valence band discontinuity is less than 50 meV between 360 K and 260 K, whereas it changes sign when the temperature decreases below 260 K, the two bandgaps becoming nested within each other. These properties are also discussed for the other kinds of sample and related to the mechanisms which are responsible for the electrical characteristics.

The noninvasive, quantitative ability of nuclear magnetic resonance (NMR) spectroscopy to characterize small molecule metabolites has long been recognized as a major strength of its application in biology. Numerous techniques exist for characterizing metabolism in living, excised, or extracted tissue, with a particular focus on 1H‐based methods due to the high sensitivity and natural abundance of protons. With the increasing use of high magnetic fields, the utility of in vivo 1H magnetic resonance spectroscopy (MRS) has markedly improved for measuring specific metabolite concentrations in biological tissues. Higher fields, coupled with recent developments in hyperpolarization, also enable techniques for complimenting 1H measurements with spectroscopy of other nuclei, such as 31P and 13C, and for combining measurements of metabolite pools with metabolic flux measurements. We compare ex vivo and in vivo methods for studying metabolism in the brain using NMR and highlight insights gained through using higher magnetic fields, the advent of dissolution dynamic nuclear polarization, and combining in vivo MRS and ex vivo NMR approaches.

The Rapid Communications section is intended for the accelerated publication of important new results. Since manuscripts submitted to this section are given priority treatment both in the editorial office and in production, authors should explain in their submittal letter why the work justifie this special handling ARa. pid Communication should be no longer than 4 printed pages and must be accompanied by an abstract. Page proofs are sent to authors.The rotationally resolved zero-kinetic-energy electron spectra for the v+ =1, 2, and 3 vibrational levels of the predissociating A X+ state of HBr+ are reported. The results for the rapidly predissociating v+ =2 and 3 levels show that the high principal quantum number Rydberg states involved in the zero-kinetic-energy spectroscopy are unperturbed by ion core fragmentation. These data demonstrate the general applicability of this technique for rotationally resolved photoelectron spectroscopy. R1

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