209Bi Nuclei Research Articles

Local magnetic fields in antiferromagnetic Bi 2CuO 4: as seen from 63,65Cu and 209Bi nuclear resonance

A complex spin-echo spectrum of 63,65Cu and 209Bi has been observed in antiferromagnetic Bi 2CuO 4 at 4.2 K. The spectrum consists of 63,65Cu AFNR and 209Bi NQR. The Cu AFNR is characterized by the internal field H int =99 kOe at Cu nuclei and by the 63ν Q=10 MHz . It is argued that the low-limit of the internal field at the 209Bi nuclei is 4.3 kOe. The occurrence of H hf at 209Bi nuclei shows that Bi 3+ anions take part in the superexchange interaction between Cu atoms along the Cu–O–Bi–O–Cu bonds.

Cascade-Exciton Model Analysis of Nucleon-Induced Fission Cross Sections of Lead and Bismuth at 45- to 500-MeV Energies

An extended version of the cascade-exciton model (CEM) of nuclear reactions is applied to analyze nucleon-induced fission cross sections for 209Bi and 208Pb nuclei in the 45- to 500-MeV energy range. The available data on linear momentum transfer are analyzed as well. The results are compared with analytical approximations resulting from a comparative critical analysis of all available experimental data. Systematic discrepancies between calculations and experimental data are revealed. A modification of the CEM is proposed, which significantly improves the model predictions for projectile energies above 100 MeV.

Observation of 63,65Cu and 209Bi nuclear resonance in antiferromagnetic Bi 2CuO 4

A complex spin-echo spectrum of 63,65Cu and 209Bi has been observed in various ceramic and single-crystal samples of Bi 2CuO 4 in antiferromagnetic phase at a temperature of 4.2 K. The spectrum consists of 63,65Cu AFNR and 209Bi NQR with a complex structure of resonance lines due to magnetic inequivalency of Bi atoms and a large asymmetry parameter. The Cu AFNR is characterized by the internal field H int≈99 kOe at Cu nuclei and by the quadrupole frequency 63 ν Q ≈10 MHz. The obtained value of H int corresponds to 0.82 μ B for the Cu 2+ magnetic moment. It is shown that the low limit of the internal field at 209Bi nuclei is approximately 4.3 kOe and consists of the dipolar field H dip=0.85 kOe and the hyperfine field H hf which essentially exceeds H dip. The occurrence of H hf at 209Bi nuclei shows that Bi 3+ anions take part in the superexchange interaction between Cu atoms along the Cu–O–Bi–O–Cu bonds.

NUCLEAR ANAPOLE MOMENT IN RELATIVISTIC MODEL AND ITS EFFECT IN ATOMIC PARITY VIOLATION MEASUREMENTS

An expression for nuclear anapole moment is derived within a valence nucleon relativistic mean-field nuclear model. The anapole moment parameter values are calculated for 133Cs, 85Rb, and 209Bi nuclei. The result reproduces the observed difference between hyperfine E1 transition amplitudes in 133Cs within the experimental accuracy. The change in the optical polarization rotation angle, induced by the parity violating electron-anapole interaction, in Bi is also calculated.

Cross sections of the (HI, αn) channel in the cold-fusion-type reactions 209Bi+ 40Ar and 208Pb+ 37Cl

By applying an off-line radiochemistry technique, cross sections for the production of the isotope 240 Cm(T 1 2 =27 d) in the cold-fusion-type reactions 209Bi+ 40Ar and 208Pb+ 37Cl at the bombarding energy E lab⩽230 MeV were determined to be 0.5±0.2 nb and 0.6±0.3 nb, respectively. The production of 240Cm was attributed to the 1n-deexcitation channel of the composite systems 249Md and 245Es. At the same time, the measured 240Cm production cross sections represent upper cross-section limits for the (HI, αn) channel of the reactions under study. These upper limits are about 100 times lower than the cross-section values reported recently by Nomura et al. for the ( 40 Ar, αx n) channels with x=1,2 of the 209Bi+ 40Ar reaction at E lab=208 MeV. In the context of the above measurements, presented and discussed is the up-to-date summary of the available evidence on cross sections of the (HI, αxn) channels in the cold-fusion-type reactions induced by projectiles ranging from 37Cl to 50Ti on targets of 203,205Tl, 208Pb, and 209Bi nuclei. Appreciable EC(β +)-delayed or/and spontaneous fission effects were detected in the 209Bi+ 40Ar, 208Pb+ 37Cl, and 206Pb+ 37Cl reactions. The obtained data point, in particular, to the EC(β +)-delayed fission occuring in the decay chains ▪ and ▪.

Fission and particle evaporation following stopped-negative-pion absorption in 209Bi

Fission and particle evaporation following stopped- π − absorption were measured for 209Bi. The fission probability per captured π − was obtained as W f = (3.01 ± 0.34) × 10 −3 from the number of fission tracks observed in the mica track detector and that of π − stopped in the Bi target. The latter was derived from the observed absolute intensities of pionic Bi X-rays. The isotopic yield distributions for the ( π −, xn) and ( π −, pxn) reactions were also determined by in-beam and activation γ-ray measurements. From the analysis of the fission probability and the product-yield distribution, it was concluded that the thermally equilibrated nuclear states have a wide energy distribution and rather low excitation energies (∼50 MeV) compared to the initially involved energy of 140 MeV. A model was proposed for the formation and decay of 209Bi nuclei excited by the capture of the stopped π −. The model well reproduces the experimental results.

Concentration and temperature dependent nuclear relaxation in liquid In-Sn, Bi-Sn and In-Pb, Bi-Pb alloys

The longitudinal nuclear relaxation rates R(c,T) have been measured for the 115In and 209Bi nuclei in liquid alloys of IncSn1-c, BicSn1-c and IncPb1-c, BicPb1-c within the concentration and temperature ranges 0.1<or=c<or=1.0 and 400K<or=T<or=640K, respectively. Although the magnetic dipolar rate Rm exceeds the electric quadrupolar rate Re by almost an order of magnitude, both the separation of R into Rm and Re and of Re into its coherent part Re,coh and its incoherent part Re,inc could be carried out to approximately 10%. Details of the spectrometer (combination of a commercial pulse set up with an on line computer) and of the alloy preparation (capillary bunch samples) are given. The concentration and temperature dependence of both parts of Re can be described by the current theory of Re(c,T) for random substitutional metallic alloys.

Elastic scattering and total reaction cross-sections for the interaction of 12.8 MeV deuterons with 12C, 58Ni, 60Ni and 209Bi nuclei

The differential cross-sections for the elastic scattering of 12.8 MeV deuterons by 12C, 58Ni, 60Ni and 209Bi have been measured and the corresponding reaction cross-sections determined by summing the partial reaction cross-sections. These data are analysed using the optical model of the interaction.