High-resolution in-beam particle spectroscopy --New results on prompt proton emission from 58Cu

Prompt proton decay lines in ⁵⁸Cu have been studied by means of high-resolution in-beam particle-γ coincidence spectroscopy using the GAMMASPHERE Ge-detector array in conjunction with a dedicated set of ancillary detectors including four ΔE-E silicon-strip telescopes. High-spin states in ⁵⁸Cu have been populated via the heavy-ion fusion-evaporation reaction ²⁸Si(³⁶Ar, 1α1p1n) at 148 MeV beam energy. The full-width at half maximum for the proton peak could be reduced significantly compared to earlier experiments. The results indicate that only one prompt proton decay branch exists in the decay-out of the well-deformed band of ⁵⁸Cu. Received: 11 March 2002 / Accepted: 10 April 2002     

Levels in 138Ce by in-beam spectroscopy

Gamma ray and conversion electrons from levels in ¹³⁸Ce have been studied following the ¹³⁹La(p, 2n)¹³⁸Ce and ¹³⁶Ba(α, 2n)¹³⁸Ce reactions. A level scheme, based on the measurement of conversion coefficients, of gamma-ray angular distributions and excitation functions and of gamma-gamma coincidences, is proposed and compared with findings by other authors. Some transitions observed lead to levels not previously identified in gamma-ray work; in other cases new spin and/or parity assignments have been given. An indication on the nature of some of the observed states is obtained by comparing the experimental data with the predictions of the ALAGA model and of the IBM-2 model.     

Heterodyne coincidence spectroscopy

A new type of light-scattering experiment, which should measure directly the triple static structure factor S ⁽³⁾ (k, q) of a fluid, is proposed. S ⁽³⁾(k, q) is the full spatial Fourier transform of the equilibrium triplet distribution function g ⁽³⁾(r ₁, r ₂, r ₃). The experiment may also be used to study dynamic correlation functions of the form <a_k (t)a_q (t′)a_k_q(t″)> (where a_k () is the kth spatial Fourier component of the density), thereby giving new information on mode-mode coupling. The method obtains its information from triple correlations in the arrival of scattered photons at three detectors. The detectors must be operated in the heterodyne mode (i.e. with a local oscillator); the scattering volume must be much larger than the volume over which molecular positions are correlated. Comparison is made with previous analyses of other multi-detector experiments.     

Development in time-differential in-beam Mössbauer spectroscopy

An overview of results on static and dynamic properties of single Fe atoms implanted into Si, Ge and ZnS as investigated with in-beam Mössbauer spectroscopy (IBMS) is given. The potential and limitations of the method are discussed.This work was supported in part by Gesellschaft für Schwerionenphysik Darmstadt and Bundesministerium für Forschung und Technologie, Bonn.     

Advances in time-differential in-beam Mössbauer spectroscopy

The development of in-beam Mössbauer spectroscopy is described. The potential of the recently applied time-differential technique is discussed. An overview of some recent experimental results is given.     

Auger photoelectron coincidence spectroscopy

Auger photoelectron coincidence spectroscopy (APECS) is a technique that provides us with unique information and a chance to gain insight into the significance of processes in the Auger spectra of atoms in solids. Hence it is a great aid in our understanding of the Auger process in atoms where electron correlations are strong. Despite the first demonstration of the technique more than 20 years ago, there are still very few working experiments. The reasons why, and the ways forward are discussed.     

High-resolution gamma-ray spectroscopy

To obtain the highest possible resolution in a measurement has always been one of the major challenges for experimental physicists because increased resolution generally results in progress. At the Institut Laue-Langevin, gamma rays emitted after neutron capture can be recorded with parts-permillion resolution. This is achieved by diffracting the gamma rays on highly perfect Sior Ge crystals. Precise measurement of the Bragg angles and the crystal lattice spacings permits the determination of wavelengths or energies. This outstanding resolving power allows the measurement of extremely small Doppler effects caused by the emission of primary gamma rays. These so-called gamma-ray-induced Doppler broadening measurements have given rise to applications in both nuclear and condensed matter physics.     

Emission-depth-selective auger photoelectron coincidence spectroscopy

The collision statistics of the energy dissipation of Auger and photoelectrons emitted from an amorphized Si(100) surface is studied by measuring the Si 2p photoelectron line as well as the first plasmon loss peak in coincidence with the Si-LVV Auger transition and the associated first plasmon loss. The Si 2p plasmon intensity decreases when measured in coincidence with the Si-LVV peak. If measured in coincidence with the Si-LVV plasmon the decrease is significantly smaller. The results agree quantitatively with calculations accounting for surface, volume, and intrinsic losses as well as elastic scattering in a random medium. In this way one can determine the average emission depth of individual electrons by means of Auger photoelectron coincidence spectroscopy, which therefore constitutes a unique tool to investigate interfaces at the nanoscale level.     

Ultra-sensitive in-beam \gamma -ray spectroscopy for nuclear astrophysics at LUNA

Ultra-sensitive in-beam -ray spectroscopy studies for nuclear astrophysics are performed at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator, deep underground in Italy’s Gran Sasso laboratory. By virtue of a specially constructed passive shield, the laboratory -ray background for < 3 MeV at LUNA has been reduced to levels comparable to those experienced in dedicated offline underground -counting setups. The -ray background induced by an incident -beam has been studied. The data are used to evaluate the feasibility of sensitive in-beam experiments at LUNA and, by extension, at similar proposed facilities.     

New in-beam Mössbauer spectroscopy station at the Budapest Research Reactor

We report about a new in-beam Mössbauer station which is intended to utilize the cold neutron source and guide system installed on the 10th beam line of the Budapest Research Reactor. This new in-beam facility enables us to broaden the number of nuclides accessible for Mössbauer studies in various materials. In this article we describe our new system and summarize the possibilities of its application to Mössbauer spectroscopy.     

High-resolution Brillouin spectroscopy of water

An experimental set-up is described for measuring, with high resolution, the hypersound-phase velocity and damping by means of Brillouin spectroscopy in the Giga-Hertz range. Measurements on water at 20°C between 3 and 6 GHz are presented showing no observable onset of dispersion in this region. Due to the high-power single-frequency HeNe-laser used and due to an effective collection of Brillouin-scattered light our experimental error is far smaller and the data are more reliable than in earlier investigations. Supported by the “Deutsche Forschungsgemeinschaft”.     

High-resolution diode-laser spectroscopy of calcium

Saturated-absorption signals on the calcium 657 nm transition are observed by direct absorption using diode lasers and a high flux atomic-beam cell. Line-widths as narrow as 65 kHz are observed with a high signal-to-noise ratio. Prospects for using this system as a compact wavelength/frequency reference are considered.     

Many-body effect in Auger-photoelectron coincidence spectroscopy spectra

When the shakeup/down excitations are not negligible in the core-level electron ionization, the photoelectron spectral peak measured in coincidence with a selected singles (noncoincidence) Auger-electron spectral peak does not necessarily coincide with the singles one. We discuss how the interference between the core-hole decay of a fully relaxed core-hole state and that of an incompletely relaxed one via the interaction between the final states created by the respective core-hole decays, affects the kinetic energy shift and asymmetrical lineshape change of the coincidence photoelectron spectrum compared to the singles one. When the final-state interaction is considerable, the interference reduces much the energy shift and the asymmetrical lineshape change. By the Auger-photoelectron coincidence spectroscopy (APECS) we can study the interference effect which does not manifest in the singles photoelectron spectrum. We discuss also the interference effect when the core-hole decay rates of both the fully relaxed core-hole state and the incompletely relaxed one depend critically on the changes in both the Auger-electron kinetic energy and the final-state potential. The effect is fairly independent of the changes.     

The nonelastic projectile break-up cross section from particle-gamma coincidence measurements for the 6li + 40ca reaction at 156 mev

The cross sections for nonelastic break-up modes have been studied for the ⁶Li + ⁴⁰Ca reaction at E_Li = 156 MeV. Gamma-ray spectra from target-like residual nuclei were measured in coinci- dence with beam-velocity projectile fragments and a value for the nonelastic break-up cross section σ^b.u_non = 582 ± 110 mb has been found. Together with results of inclusive charged-particle measure- ments we infer for the total break-up cross section σ^b.u_tot = 930 ± 115 mb comprising about 50% of the total reaction cross section. The nonelastic contribution of the break-up reaction appears to be less than predicted by the DWBA break-up theory. This result is directly evident from the differential cross sections by comparing inclusive and exclusive results.     

High-resolution laser spectroscopy in fast beams

A method of obtaining narrow absorption lines is proposed, based on a simple property of accelerated beams, which would yield a resolution of a few megahertz at optical frequencies. Important linewidth contributions and systematic shifts are estimated. Applications to optical and mass spectroscopy are discussed, with emphasis on investigations of short-lived isotopes.     

Conversion--electron gamma--ray coincidence spectroscopy of superdeformed 135Nd

Three mini-orange conversion–electron spectrometers and four Euroball Ge Cluster detectors have been used for γ–e^- coincidence spectroscopy of superdeformed ¹³⁵Nd. Transitions within the superdeformed band are shown to have the expected E2 multipolarity. The 766.5–keV transition which links the band to a positive-parity state has a conversion coefficient consistent with M1 multipolarity. Consequently, positive parity is deduced for the superdeformed band. No evidence for E0 transitions was found. Received: 22 December 1997 / Revised version: 19 January 1998