Search results for "Spectral"
showing 10 items of 3116 documents
Lifetime measurements probing triple shape coexistence in ^{175}Au
2011
Lifetimes of the low-lying excited states in the very neutron-deficient nucleus ${}^{175}$Au have been measured by the recoil-distance Doppler-shift method using $\ensuremath{\gamma}$-ray spectra obtained with the recoil-decay tagging technique. Transition quadrupole moments and reduced transition probabilities extracted for this odd-$Z$ nucleus indicate the existence of three different shapes and the competition between collective and noncollective structures.
In-beam spectroscopic studies of shape coexistence and collectivity in the neutron-deficientZ≈ 82 nuclei
2016
In the present paper we focus on studies of shape coexistence in even-mass nuclei in the neutron-deficient Pb region. They are based on experiments carried out using tagging techniques in the Accelerator Laboratory of the University of Jyväskylä, Finland. Excited states in many of these nuclei can only be accessed via fusion-evaporation reactions employing high-intensity stable-ion beams. The key features in these experiments are high selectivity, clean spectra and instrumentation that enables high count rates. We review three spectroscopic highlights in this region. peerReviewed
Quadrupole variation of projected spectra of even Ti isotopes
1975
In the present work we study the dependence of projected good $J$ states on the quadrupole moment. In order to achieve this, the quadrupole-moment-depenent generalized deformed BCS (DBCS) wave functions have been computed after minimizing the constrained Hamiltonian ${H}_{q}=H\ensuremath{-}\ensuremath{\lambda}N\ensuremath{-}\ensuremath{\mu}Q$. The calculation assumes the existence of a $^{40}\mathrm{Ca}$ spherical core. The two body residual interaction between the valence nucleons is determined by using the $^{42}\mathrm{Sc}$ spectrum for the $T=0$ force and the $^{49}\mathrm{Ca}$ spectrum for the $T=1$ force. The result of the calculation shows that the projected spectra in general cannot…
Modelling of Magnetic Resonance Spectra Using Mixtures for Binned and Truncated Data
2007
Magnetic Resonance Spectroscopy (MRS) provides the biochemical composition of a tissue under study. This information is useful for the in-vivo diagnosis of brain tumours. Prior knowledge of the relative position of the organic compound contributions in the MRS suggests the development of a probabilistic mixture model and its EM-based Maximum Likelihood Estimation for binned and truncated data. Experiments for characterizing and classifying Short Time Echo (STE) spectra from brain tumours are reported.
Asymmetric linear Ge(Li)Ge(Li) sum-peak coincidence spectrometer
1972
Abstract An asymmetric linear Ge(Li)Ge(Li) sum-peak coincidence spectrometer configuration has been designed and tested. In this system, the ratio of the gains of two detector-amplifier chains is chosen around 1.2 to 1.3, and the pulse amplitudes or addresses due to coincident events are summed. The simple method introduced involving a single run which results in two spectra (separated according to which detector records the larger energy) appears to be quite useful in γγ coincidence and directional correlation measurements, especially in laboratories where no event-by-event data acquisition hardware are available.
Microscopic nuclear-structure calculations for the solar-neutrino detector and close-lying isobars
2003
In the present solar-neutrino experiments, mainly observing the pp contribution of the solar-neutrino flux, an important role is played by 71Ga. The structure of this detector nucleus and three of its isobars have been calculated by using the microscopic quasiparticle–phonon model. Using a realistic effective two-body interaction in a realistic valence space, the method yielded energy spectra in good agreement with experiments. The calculated logft values for a number of spontaneous and neutrino-induced Gamow–Teller transitions, when compared with the experimental results, gave qualitatively correct but overestimated transition-strength values in most cases.
Resonant Nuclear Fusion Processes and the Gamma Rays of SS 433
1984
Gamma-ray spectral lines have recently been reported coming from the celestial object SS 433, which is known to emit high-speed jets in opposite directions. The proposed identification of the lines as coming from fusion reactions on nitrogen nuclei as part of the carbon-nitrogen-oxygen cycle operating in the jets has now received observational support. Predictions of strengths and widths of additional lines which, if seen, would provide valuable new information about conditions giving rise to the jets are presented.
Evolution ofπ0Suppression inAu+AuCollisions fromsNN=39to 200 GeV
2012
Neutral-pion pi(0) spectra were measured at midrapidity (vertical bar y vertical bar < 0.35) in Au + Au collisions at root s(NN) = 39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1 < p(T) < 10 GeV/c. The high-p(T) tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p + p collisions. The nuclear modification factors (RAA) show significant suppression, with a distinct energy, centrality, and p(T) dependence. Above p(T) = 7 GeV/c, R-AA is similar for root sNN = 62.4 and 200 GeV at …
Corrections for positon annihilation in flight in nuclear spectrometry
1973
Abstract Theories of positon single- and two-quanta annihilation in flight, the Fermi beta-decay theory, and theories of positon energy loss are used in calculations of total probabilities of annihilation in flight of positons in continuous spectra. The results are given in a nomogram useful in correcting for positon annihilation in flight in various nuclear-spectrometry experiments. Confirmation of the theoretical basis employed was obtained by comparing total absolute probabilities for annihilation in flight of 62 Cu positons in Perspex, copper, cadmium and lead, using a new differential method. The agreement with the theory was found to be excellent. A method for obtaining “correct” posi…
Determination of Qβ values from endpoint energies of beta spectra
1979
Abstract A plastic scintillator telescope is described for determining beta endpoint energies up to 15 MeV. The response function of the telescope was measured using monoenergetic electrons from a betatron. A nonlinear procedure for unfolding the measured beta spectra on the basis of the experimental response function was tested successfully.