81,271 research outputs found
High-resolution study of T-z =+1 -> 0 Gamow-Teller transitions in the Mg-26(He-3,t)Al-26 reaction
No full textIn order to study the T-z = +1 -> 0 Gamow-Teller (GT) transitions in the mass A = 26 system, a charge-exchange reaction Mg-26(He-3,t)Al-26 was performed at an incident energy of 140 MeV/nucleon and scattering angle at and near 0 degrees, where T-z is the z component of isospin T defined by (N - Z)/2. In this (p, n)-type reaction, it is expected that GT states with T = 0, 1, and 2 are excited. An energy resolution of Delta E = 23 keV allowed us to study many discrete states. Most of the prominent states showed 0 degrees-peaked angular distributions, which suggested that they are the states excited by Delta L = 0 GT transitions. Candidates of GT states were studied up to an excitation energy E-x = 18.5 MeV. The reduced GT transition strengths, B(GT), were derived assuming the proportionality between cross sections and B(GT) values. Standard B(GT) values were obtained form the Si-26 beta decay, where the mirror symmetry of T-z = +/- 1 -> 0 GT transitions was assumed. The GT strength, as a whole, is divided in two energy regions: the region of up to 8.5 MeV and the higher-energy region of 8.5-12.8MeV, where the strength in the latter region distributed like a resonance. The obtained GT strength distribution is compared with the results of random phase approximation calculations. The T = 2 GT states are expected in the region E-x >= 13.5 MeV. By comparing with the results of (n, p)-type Mg-26(d, He-2)Na-26 and Mg-26(t, He-3)Na-26 reactions, the isospin symmetry of T = 2 GT states is discussed. Owing to the high-energy resolution, we could study the decay widths Gamma for the states in the E-x > 9 MeV region. The T = 2 state at 13.592 MeV is not noticeably wider than the experimental energy resolution. The narrow width of the state is explained in terms of isospin selection rules
Detrital zircon and apatite (U‐Th)/He geochronology of intercalated baked sediments: a new approach to dating young basalt flows
No full textSimple numerical models suggest that many basaltic lava flows should sufficiently heat the sediments beneath them to reset (U‐Th)/He systematics in detrital zircon and apatite. This result suggests a useful way to date such flows when more conventional geochronological approaches are either impractical or yield specious results. We present here a test of this method on sediments interstratified with basalt flows of the Taos Plateau Volcanic Field of New Mexico. Nineteen zircons and apatites from two samples of baked sand collected from the uppermost 2 cm of a fluvial channel beneath a flow of the Upper Member of the Servilleta Basalt yielded an apparent age of 3.487 ± 0.047 Ma (2 SE confidence level), within the range of all published 40Ar/39Ar dates for other flows in the Upper Member (2.81–3.72 Ma) and statistically indistinguishable from the 40Ar/39Ar dates for basal flows of the Upper Member with which the studied flow is broadly correlative (3.61 ± 0.13 Ma). Given the high yield of 4He from U and Th decay, this technique may be especially useful for dating Pleistocene basalt flows. Detailed studies of the variation of (U‐Th)/He detrital mineral dates in sedimentary substrates, combined with thermal modeling, may be a valuable tool for physical volcanologists who wish to explore the temporal and spatial evolution of individual flows and lava fields.</p
(HE-3,T) CHARGE-EXCHANGE REACTIONS AT E(HE-3)=450 MEV, THETA=0-DEGREES
No full textSpin-isospin excitations in nuclei have been studied by means of the (He-3,t) reactions at 450 MeV on the targets Be-9, (nat)C, Si-28, Ni-58, Ni-62, Zr-90, Sn-118, Sn-120, 124Sn, and Sm-154. The new spectrometer ''Grand Raiden'' was employed for the (He-3,t) study for the first time. Observed (He-3,t) spectra at 0-degrees show remarkable similarity with those from the (p,n) results at intermediate energies, suggesting a simple direct reaction mechanism for the (He-3,t) reaction at 450 MeV. The Gamow-Teller (GT) resonances and the spin-flip DELTAL = 1 resonances are excited very strongly. A fine structure of the GT resonances in medium-heavy nuclei is observed with an energy resolution of 210 keV. It is demonstrated that the (He-3,t) reaction at 450 MeV is a powerful tool to study the spin-isospin excitations in nuclei.</p
(HE-3,T) CHARGE-EXCHANGE REACTIONS AT E(HE-3)=450 MEV, THETA=0-DEGREES
No full textSpin-isospin excitations in nuclei have been studied by means of the (He-3,t) reactions at 450 MeV on the targets Be-9, (nat)C, Si-28, Ni-58, Ni-62, Zr-90, Sn-118, Sn-120, 124Sn, and Sm-154. The new spectrometer ''Grand Raiden'' was employed for the (He-3,t) study for the first time. Observed (He-3,t) spectra at 0-degrees show remarkable similarity with those from the (p,n) results at intermediate energies, suggesting a simple direct reaction mechanism for the (He-3,t) reaction at 450 MeV. The Gamow-Teller (GT) resonances and the spin-flip DELTAL = 1 resonances are excited very strongly. A fine structure of the GT resonances in medium-heavy nuclei is observed with an energy resolution of 210 keV. It is demonstrated that the (He-3,t) reaction at 450 MeV is a powerful tool to study the spin-isospin excitations in nuclei.</p
He must have loved the earth, the sea, the sky,
No full textRecited by Tommy Gosnell (in place of Mrs. Horace Smith) Springdale, Arkansas November 3, 1958
Reel 271, Item 27
To the Author of a Psalm
He must have loved the earth, the sea, the sky,
The powers that swing the universe along,
And all that is and has been and could be To sing so brave and beautiful a song.
He must have fingered ivory and jade And tasted with a discriminating tongue And deeped the glory that the man moon made,
A dim mysterious world that he was young.
He must have known the alchemy of life,
The day flooding in on waves of yellow mist,
Reclaiming from the oblivion night Drops of gold and wine of anethyst.
He must have loved this earth, yet he is dead.
Lifeless is his eager foot, his curious hand.
Or am I faithless?has he found instead A still more golden road to Smarkland?
Collected by Karl. T. Gosnell For Mary C. ParlerFunding for digitization provided by the Arkansas Humanities Council and the Happy Hollow Foundation
More on Soft Theorems: Trees, Loops and Strings
No full textThe work of S. H. is
supported by Zurich Financial Services Membership and
the Ambrose Monell Foundation. The work of Y.-t. H. is
supported by the National Science Foundation Grant
No. PHY-1314311 and MOST Grant No. 103-2112-M002-025-MY3.
The work of C. W. is supported by the
Science and Technology Facilities Council Consolidated
Grant No. ST/J000469/1, “String theory, gauge theory and
duality.” The work of M. B. is partially supported by the
ERC Advanced Grant No. 226455, “Superfields
Wave turbulence of a rotating array of quantized vortices in the T → 0 temperature limit
No full textThe dynamics of quantized vortices in the zero temperature limit is currently of great interest, particularly in the case of the Fermi superfluid He-B. Here we study wave turbulence, generated by the librating motion of a rotating cylindrical container filled with He-B, in the limit of vanishing viscous forces at temperatures . The polarization of the quantized vortices with respect to the axis of rotation is measured using non-invasive NMR techniques. We observe a decrease of the polarization when the librating motion is started, and a two-stage relaxation process when the modulation of the rotation velocity is stopped. The first relaxation process is associated with the dissipation of large-scale flow stored in inertial waves and the solid body rotation of the vortex array. From the decay of these energy reservoirs we determine the rate of energy dissipation of large-scale flow. The later second process is related to the relaxation of Kelvin waves on individual vortices. This process is monitored by the recovery of the polarization. The existence of a Kelvin wave cascade at the lowest temperatures is currently a central open question. We supply some evidence for the cascade
Rare Gas-Halogen Atom Interaction Potentials from Molecular Beam Studies: I(2P3/2) + Kr and Xe (1S)
No full textInteraction Potentials for Br(2P) + Ar, Kr and Xe (1S) by the Crossed Molecular Beams Method
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