Light-particle emission in the reaction of 93Nb + 14N at 132, 159 and 208 MeV

Nonequilibrium light-particle emissions have been investigated in the reaction ⁹³Nb + ¹⁴N at 132, 159 and 208 MeV by measuring inclusive differential cross sections of p, d, t, ³He and α. The experimental data were analyzed in terms of three models: (i) an extended exciton model, (ii) a coalescence model, and (iii) a moving thermal source model. The angle-integrated energy spectra of the protons were well described by the extended exciton model in which projectile nucleons were assumed to be transferred to the target one by one, but those of composite particles were not. On the other hand, the composite particle spectra (except for α at forward angles) were successfully described by the coalescence model using spectra consistent with those for the protons. Extracted coalescence radii P₀ were about 140 MeV/c for d and t, and about 220 MeV/c for α. The light-particle spectra were also fitted by the moving-source model assuming isotropic emission from a source moving with approximately half of the beam velocity and with much higher temperature than that of the compound nucleus. Extracted temperatures followed the systematics of a recent compilation for the various reactions. A discussion of these analyses is given.     

Studies on mixed chelates,part IX. A new mixed nickel(II) chelate which assumes 4-, 5-, and 6-coordinate structures in various organic solvents

Summary A new mixed nickel(II) chelate, Ni(tmen)(acac)(NCS) · 0–1 H₂O, was prepared. It was found that this (anhydrous) chelate changes from a 6-coordinate, probably dimeric structure in the solid state to (i) a 5-coordinate square pyramidal, (ii) a 4-coordinate square planar and (iii) 6-coordinate solvated structure, according to the solvent used.     

Generation of Oriented Matroids—A Graph Theoretical Approach

We discuss methods for the generation of oriented matroids and of isomorphism classes of oriented matroids. Our methods are based on single element extensions and graph theoretical representations of oriented matroids, and all these methods work in general rank and for non-uniform and uniform oriented matroids as well. We consider two types of graphs, cocircuit graphs and tope graphs, and discuss the single element extensions in terms of localizations which can be viewed as partitions of the vertex sets of the graphs. Whereas localizations of the cocircuit graph are well characterized, there is no graph theoretical characterization known for localizations of the tope graph. In this paper we prove a connectedness property for tope graph localizations and use this for the design of algorithms for the generation of single element extensions by use of tope graphs. Furthermore, we discuss similar algorithms which use the cocircuit graph. The characterization of localizations of cocircuit graphs finally leads to a backtracking algorithm which is a simple and efficient method for the generation of single element extensions. We compare this method with a recent algorithm of Bokowski and Guedes de Oliveira for uniform oriented matroids. Received November 1, 2000, and in revised form May 11, 2001. Online publication November 7, 2001.     

Precise measurement of magnetic moment of short-lived β-emitting nuclei ~(12)B (I~π=1~+,T_(1/2)=20.18 ms)

1 Introduction The production of nuclear spin polarization and the maintenance of the nuclear po-larization in a stopper are the essential requirement for the measurement of nuclear magnetic and electric quadrupole moments of the b-emitting nuclei by the ?NMR and b-NQR (b-ray detected Nuclear Magnetic Resonance and b-ray detected Nuclear Quad-rupole Resonance) technique. This requirement can be realized by the selection tech-nique of the incident particle energy of the nuclear reaction th…     

Scintillation properties of the Yb-doped YAlO3 crystals

Yb³⁺-doped YAlO₃ single crystals were grown by the Czochralski method with a radio frequency heating system. The starting melt compositions of Y_1−xYb_xAlO₃ were varied as x=0.02, 0.1, 0.2, 0.3 and 0.45. Photo- and thermo-luminescence characteristics including emission decays were measured within 4–300 K. Very fast charge transfer luminescence of Yb³⁺ was found, with the typical double peak spectrum at 345 and 525 nm. At room temperature the photoluminescence and scintillation decay curves show a leading subnanosecond decay component without any additional slower processes. The high density of Yb-rich YAlO₃ makes this material a promising candidate for fast scintillators.     

On log canonical divisors that are log quasi-numerically positive

Let (X Δ) be a four-dimensional log variety that is projective over the field of complex numbers. Assume that (X, Δ) is not Kawamata log terminal (klt) but divisorial log terminal (dlt). First we introduce the notion of “log quasi-numerically positive”, by relaxing that of “numerically positive”. Next we prove that, if the log canonical divisorK _X+Δ is log quasi-numerically positive on (X, Δ) then it is semi-ample.     

Magnetic resonance in relaxed excited states AX and AT of Ga+ in alkali halides

The optical detection technique is used to observe magnetic resonance in the excited states ³T_1u of Ga⁺ in KI, KC? and NaC?. The relaxed excited states A_X and A_T display trigonal and tetragonal symmetry respectively, as a result of a static Jahn-Teller effect. Furthermore the coupling to E_g and T_2g modes is found to be nearly equal in KI : Ga⁺, as already observed in KBr : Ga⁺.