Observation of 239Pu nuclear magnetic resonance.

In principle, the spin-½ plutonium-239 ((239)Pu) nucleus should be active in nuclear magnetic resonance spectroscopy. However, its signal has eluded detection for the past 50 years. Here, we report observation of a (239)Pu resonance from a solid sample of plutonium dioxide (PuO(2)) subjected to a wide scan of external magnetic field values (3 to 8 tesla) at a temperature of 4 kelvin. By mapping the external field dependence of the measured resonance frequency, we determined the nuclear gyromagnetic ratio (239)γ(n)(PuO(2))/2π to be 2.856 ± 0.001 megahertz per tesla (MHz/T). Assuming a free-ion value for the Pu(4+) hyperfine coupling constant, we estimated a bare (239)γ(n)/2π value of ~2.29 MHz/T, corresponding to a nuclear magnetic moment of µ(n) ≈ 0.15µ(N) (where µ(N) is the nuclear magneton).

Raman spectroscopy applications of an imaging photomultiplier tube.

A Raman spectroscopy system having an unprecedented combination of high sensitivity and low noise has been built incorporating an imaging (2-D) photomultiplier tube. The number of photons detected for a vibrational band approaches the theoretical limit set by the Raman cross section and experimental configuration. A detector dark count of 10(-4) counts/s/pixel is the major electronic source of noise. The spectrum of air reveals low concentration gas components, specifically (16)O(18)O and CO(2). Vibrational Raman spectra are obtained from solid samples as thin as 20 nm with low laser powers, e.g., 6.5 mW. The imaging photomultiplier yields 1-D (along the focused laser beam) Raman images of interfaces or concentration gradients.

Mapping materials properties with Raman spectroscopy utilizing a 2-D detector.

An imaging Raman system based on a 2-D detector and capable of collecting simultaneously 1024 spatially resolved spectra has been constructed. Hardware and software are described which allow real time analysis of the spectral data, leading to a large reduction in the data storage requirements. The analysis yields a 1-D profile (1024 points) across the sample of chemical or physical properties that are distinguishable by their Raman spectral features. Sample translations, along with repeated collection and analysis cycles, allow 2-D maps of chemical or physical properties to be generated rapidly. The spatial resolution and spectral precision are 5microm and 0.16 cm(-1) respectively. Applications to the analysis of phase transformed zones in microengineered zirconias and to measurement of an in situ temperature profile of a single carbon fiber are presented. In a typical application, 66,560 Raman spectra from an 8- x 6-mm area on a partially stabilized zirconia sample were collected and analyzed in 5.4 h to produce a 2-D map of the fraction of tetragonal phase transformed to monoclinic phase during crack propagation.