Search results for "DIPOLE"
showing 10 items of 982 documents
Magnetic moment of the S11 (1535) resonance
2003
Abstract The γ p a γη p reaction in the S 11 (1535) resonance region is investigated as a method to access the S 11 (1535) magnetic dipole moment. To study the feasibility, we perform calculations of the γ p → γη p process within an effective Lagrangian approach containing both the S 11 resonant mecanism and a background of non-resonant contributions. Predictions are made for the forthcoming experiments. In particular, we focus on the sensitivity of cross sections and photon asymmetries to the S 11 (1535) magnetic dipole moment.
On the decay of compound nuclei following alpha-particle and12C induced reactions
1981
Multiple coincidence rates have been measured using a detector system consisting of a Ge(Li) spectrometer and eight NaI(Tl) or eight liquid scintillators. Reactions induced byα-particles with energies of 51–55 MeV and 118 MeV12C ions are studied. The data are analysed to give the first and second central moments of the distribution of the number ofγ-rays feeding individual levels in the final nuclei. When these numbers are compared to spin distributions calculated with the statistical model code GROGI the relative importance of dipole and quadrupole deexcitation modes can be ascertained. In particular, in the122Te(α, 4n)122Xe reaction theγ-decay prior to the entry into the ground band is we…
Decay properties of very-high-spin states in transitional Er nuclei aroundA=154
1986
Theγ ray continuum structures of the transitional Er isotopes withA∼154 are studied using the reaction74Ge(84Kr,xn)158−xEr atElab=340 MeV. The measurements include energy spectra, total energies, multiplicities, angular distributions and lifetimes using the DSAM method. The analysis of data confirms the previously observed two-bump structure of the continuum radiation. A meticulous subtraction of discrete contributions proves the persistence of the low-energy bump even at high spins, i.e.I>40ħ. The angular-distribution measurements assign predominant dipole structure to the bump atEγ=0.65 MeV, whereas the bump atEγ=1.3 MeV is of almost pure quadrupole character at high spins. The lifetime m…
High temperature giant dipole and isoscalar resonances
1990
We present a systematic study of the Giant Dipole Resonance (GDR) at high temperatures (T≧4 MeV) in the framework of a semiclassical approximation that uses them1 andm3 RPA sum rules to estimate the GDR mean energy. We focus on the evolution withT of the collective nature of the GDR and of theL=0, 2, 3 and 4 isoscalar resonances. We find that the GDR remains particularly collective at highT, suggesting that it might be possible to observe it experimentally even at temperatures close to the maximum one a nucleus can sustain.
Normal and transverse single tau polarization at the Z-peak
1994
Abstract We study normal (to the collision plane) and transverse (within the collision plane) single-τ polarization in τ pairs produced in e + e − unpolarized collisions at the Z -resonance. The transverse polarization component is sensitive to the anomalous weak-magnetic moment, whereas the normal polarization component is sensitive to a CP-violating weak-electric dipole moment. We show how these components of the single τ polarization are accessible from the angular distribution of its decay products. We define a CP violating asymmetry of the τ decay products which, with 10 7 Z ′s produced, provides a sensitivity of 2.3 × 10 −18 e ·cm for the weak-electric dipole moment.
Excited states in neutron deficient even-even thorium isotopes (218?A?222)
1985
The nuclei218, 220, 222Th were investigated by conversion electron andγ-ray spectroscopy after compound nucleus reactions of14N with209Bi and16, 18O with208Pb. The intenseγ-background from fission was suppressed by spectroscopy of conversion electrons andγ-rays in coincidence with the evaporation residues or theirα-decay. Level schemes were determined for218Th up toIπ=10+ and for220Th and222Th up toIπ=15−. The observed structure of218Th may be explained in the spherical shell model with residual interaction by two neutron excitation. ForN≧130 completely different level schemes are observed showing very intense, collective electric dipole transitions (B(E1)−10−2 W.u.) with energies of typica…
Evidence for three microscopically different kinds ofE1 transition in lead-region nuclei
1988
A survey of electric dipole transition rates, or B(E1) values, is done for lead-region nuclei with 82≦Z≦90 and 112≦N≦134. It is found that the major part of the E1 transitions are hindered by a factor of about 106–107 and these transitions are interpreted to proceed via admixtures of the collective 1− state. A second group, which is generally 10–100 times less hindered and is involving the πi13/2 orbital in the initial states, is suggested to proceed via the allowed πi11/2→πh9/2 admixtures in the wave functions. These two groups are compared to a third newly established category, the α-cluster or IBAp-boson mode, of the so-called vibron model.
The new FL measurement from HERA and the dipole model
2012
From the new measurement of F_L at HERA we derive fixed-Q^2 averages . We compare these with bounds which are rigorous in the framework of the standard dipole picture. The bounds are sharpened by including information on the charm structure function F_2^(c). Within the experimental errors the bounds are respected by the data. But for 3.5 GeV^2 <= Q^2 <= 20 GeV^2 the central values of the data are close to and in some cases even above the bounds. Data on F_L/F_2 significantly exceeding the bounds would rule out the standard dipole picture at these kinematic points. We discuss, furthermore, how data respecting the bounds but coming close to them can give information on questions like colour t…
High-resolution laser resonance ionization spectroscopy of $^{143-147}$Pm
2020
The European physical journal / A 56(2), 69 (2020). doi:10.1140/epja/s10050-020-00061-8
Nuclear moments and charge radii of107?111in determined by laser spectroscopy
1985
Collinear fast beam laser spectroscopy has been used to measure the hyperfine structure and isotope shift in the atomic 5s 2 5p 2 P 3/2-5s 2 6s 2 S 1/2 transition (λ=451 nm) of107–111In. Secondary beams of neutron deficient indium isotopes were prepared at the GSI on-line mass separator following fusion evaporation reactions. Magnetic dipole moments and electric quadrupole moments have been determined. The isotope shifts are discussed in terms of the change of the mean square nuclear charge radii and compared with the droplet model predictions and the deformation values calculated from the quadrupole moments.