Silver Isotopes Research Articles

Neutron Capture Cross Sections of the Silver Isotopes 107Ag and 109Ag from 2.6 to 2000 keV

Prompt neutron capture from highly enriched samples of the stable silver isotopes was measured at the Oak Ridge Electron Linear Accelerator neutron time-of-flight facility. Resonance peaks were par...

Totalβ-decay energies and mass systematics of neutron-rich silver and cadmium isotopes

Experimental total beta-decay energies of neutron-rich silver and cadmium isotopes are presented. The sources have been produced as mass-separated fission products by means of the on-line--isotope-separator technique. Beta spectra have been recorded in coincidence with different gamma transitions, and Q/sub ..beta../ values for /sup 116en-dash121/Ag, /sup 119/Cd, and /sup 121/Cd have been deduced. The atomic mass excess is derived for these nuclei, and comparisons are made with mass formula predictions.

Neutron-interferometric measurement of the coherent scattering length of the isotopes of silver

Employing a new measuring scheme with the D 18 Neutron Interferometer at the ILL, Grenoble, the thermal neutron coherent scattering lengthb c for bound atoms of natural Ag,107Ag and109Ag have been measured at the wavelengthλ=1.8742 A. The results, corrected for composition and density of the actual samples, are nat Ag:b c =5.922 (7) fm107Ag:107b c =7.555 (11) fm109Ag:109b c =4.165 (11) fm The result is in agreement with an earlier value obtained with the interferometer for nat Ag (5.932 (6)) using a different measuring scheme and a totally different sample. For nat Ag and107Ag the values determined interferometrically are ≃0.05 and ≃0.08 fm smaller, repectively, than those measured with the Christiansen filter method.

Investigations of very neutron-deficient isotopes below100Sn in40Ca-induced reactions

Very neutron-deficient isotopes of rhodium, palladium, silver, cadmium and indium in theN=50 region were studied at the GSI on-line mass separator following bombardment of58, 60, 62Ni and63, 65Cu targets with 4.0 MeV/u ions of40Ca. The known properties of the β-delayed proton precursor95m Pd were confirmed, but a search for direct proton decay of95m Ag was not successful. Beta-delayed proton activities observed at mass-numbers 94, 96, 97 and 100 were assigned to the precursors94Rh(66±14 s),96Ag(5.1±0.4s),97Cd(3 −2 +4 s) and100In. In addition,94Pd(9.0±0.5 s) was identified from β-γ-X studies. Individual decay schemes of95m96Pd and96, 98Ag are reported.

Slow neutron scattering lengths of the isotopes of silver and indium

By means of the Cristiansen filter method we measured on filters containing powder, filings or wires of silver or powder of indium oxide the coherent scattering lengths for the bound atoms of the following isotopes:b(107Ag)=7.64±0.04 fm,b(109Ag)=4.19±0.03 fmb(nat.Ag)=5.97±0.01 fm,b(113In)=5.39±0.06 fmb(115In)=4.00±0.03 fm andb(nat.In)=4.065±0.020 fm. From these values and taking account of incoherent and resonance data we deduced values for the fundamental spin state scattering lengths and incoherent cross sections. These zero energy scattering parameters and the resonance parameters for silver are consistent if bound levels of108Ag and110Ag are assumed. No indications were found for bound levels of the In isotopes.

Pd108,106(p, t)reactions and the core-coupling model

The $^{108,106}\mathrm{Pd}(p, t)^{106,104}\mathrm{Pd}$ reactions were studied at 30 MeV proton energies using a quadrupole-dipole-dipole-dipole spectrograph together with a 60 cm wire proportional counter backed by a plastic scintillator. Closely spaced multiplets of states in $^{104}\mathrm{Pd}$ of special interest were investigated at 5 keV energy resolution with a 5 cm solid state position sensitive detector. The ($p, t$) strength for population of levels in the even Pd isotopes is found to be close to the corresponding summed strength previously found for population of the core-coupled multiplets in the silver isotopes, a result in accord with a prediction of the weak coupling model.NUCLEAR REACTIONS $^{106,108}\mathrm{Pd}(p, t)$, ${E}_{p}=30$ MeV, measured $\ensuremath{\sigma}(\ensuremath{\theta})$ and level energies, DWBA analysis, deduced $L$,${J}^{\ensuremath{\pi}}$. Enriched targets, 13 keV resolution, 5 keV for some multiplets.

Isotope effect in the Knight shift of silver

The Knight shifts of the silver isotopes 107Ag and 109Ag were determined with high accuracy. Between these shifts there is a difference ΔK = K 107 - K 109 = −(17.1 ± 1.1) ppm. The relative isotope effect Δ K/ K is not in agreement with the hyperfine structure anomaly 107Δ 109.

Interpretation of the properties of the odd-mass silver isotopes in the framework of the models of De-Shalit and Alaga

The structure of the odd-mass silver nuclei is discussed in terms both of the De-Shalit weak coupling model and of the Alaga model. It is shown that these models exhibit similar features as regards the negative-parity states. A detailed comparison with experiments is performed for 109 Ag.

Analysis of superposition of two resonant lines in atomic-beam device

In a silver atomic-beam magnetic-resonance apparatus, it is possible to measure a so-called ‘superposition line’ that is a simultaneous resonance of both isotopes of silver. The letter is devoted to the analysis of the line shape of this line.

Comparison of the Isotope Effect for Diffusion of Sodium and Silver in Lithium

Separate measurements were made at 150 \ifmmode^\circ\else\textdegree\fi{}C of the simultaneous diffusion of sodium isotopes ($^{22}\mathrm{Na}$ and $^{24}\mathrm{Na}$) and silver isotopes ($^{105}\mathrm{Ag}$ and $^{110m}\mathrm{Ag}$) in lithium. The strength of the isotope effect $f\ensuremath{\Delta}K$ for sodium is 0.19 \ifmmode\pm\else\textpm\fi{} 0.01 and for silver 0.26 \ifmmode\pm\else\textpm\fi{} 0.01. These values do not correlate well with recent calculations of $\ensuremath{\Delta}K$ determined for impurity diffusion on the basis of the dynamical theory of diffusion. Measurement of the diffusion of silver in lithium is 45% greater than earlier data, and a possible explanation for this discrepancy is given.

Transitions, with change in parity, produced in 107,109Ag by coulomb excitation

Some of the low-lying energy levels of 107Ag and 109Ag were excited by Coulomb excitation using α-particles from 4.8 to 7.2 MeV. Transitions to the isomeric state ( 7 2 + ), involving a parity change, were observed both directly in the singles spectra and indirectly by the decay of the isomer. The isomer in both silver isotopes was populated by transitions from the 5 2 − level, which was strongly excited. The observed branching ratio in 109Ag for the 5 2 − → 7 2 + transition was (0.315 ± 0.09) % and for the 5 2 − → 9 2 + transition was (0.055±0.03) %. The total rate of populating the 7 2 + level from the 5 2 − level was (0.215±0.04) % in 107Ag. The level schemes have been discussed on the weak-coupling model, allowing admixtures of singleparticle wave functions to account for the weaker transitions.

Correlation effects in grain boundary diffusion

The grain boundary self-diffusion coefficient in silver has been measured using the sectioning technique, for polycrystals, 〈100〉 16° tilt bicrystals, and 〈112〉 18° tilt bicrystals over the temperature ranges 350–555°C, 400–555°C, and 350–498°C, respectively. The temperature dependence of D'δ from the Suzuoka solution is given by D'δ = 8.55 × 10 −10 exp (−17800/ RT)cm 3/sec for the polycrystals and D'δ = 3.1 × 10 −11 expt (− 11800/ RT) cm 3/sec for the 〈100〉 tilt bicrystals. The activation energy for the 〈112〉 tilt boundaries is significantly larger than that of the polycrystal or 〈100〉 tilt boundaries. The simultaneous diffusion of 105Ag and 110Ag in the grain boundaries of the polycrystals from 350–555°C and 〈100〉 tilt bicrystals at 400 and 498°C allowed for measurements of the isotope effect for grain boundary self-diffusion. The isotope effect results prove that there is very little isotopic separation during grain boundary diffusion. Within the experimental accuracies, the isotope effects for the random boundaries of the polycrystals and the 〈100〉 tilt boundaries are identical. The average value of f Δ K for the polycrystals is 0.46. This is significantly lower than the low-temperature lattice, self-diffusion isotope effect in silver. A vacancy model has been developed from which the correlation factor for diffusion along dislocations can be calculated. The isotope-effect measurements can be interpreted in terms of the modelistic calculations and many-body saddle point interactions. The results are consistent with a three-dimensional interpretation of grain boundary diffusion and a vacancy-dislocation binding energy that decrease at 0.05 to O.10 eV per atomic plane from the dislocation core. The silver isotope effect for grain boundary diffusion in polycrystalline copper at 466°C is 0.18. This value is consistent with a highly correlated vacancy mechanism.

Mass yield distribution and charge dispersion in 450 MeV proton fission of 238U

The independent and/or cumulative cross-sections of 26 isotopes of silver, cadmium, indium, tin, and antimony from the fission of 238U with 450 MeV protons have been measured. The isotopic yield distribution for these elements is presented along with the charge dispersion for six mass chains, 109, 115, 117, 125, 127 and 129. The values of the most probable charge, Zp, for 14 mass chains were calculated and the variation of A Zp with A in the mass region 100–130 was determined. For A values between 100 and 120, the value of A Zp is relatively constant at a value of 2·424±0·004 if the charge dispersion width is assumed to be constant at a value of 2·90±0·10 Z units. In the mass region, 125–129, a width of 3·21 Z units and a slightly higher value of A Zp , 2·430±0·004, are required to account for the data. A mass yield curve encompassing this region of A was also determined.

E3Isomer inAg105

An $E3$ isomer has been found in ${\mathrm{Ag}}^{105}$. The isomeric transition with half-life 7.23\ifmmode\pm\else\textpm\fi{}0.16 min is attributed to a 25.5-keV transition to the ground state. Electron-capture branching to known levels in ${\mathrm{Pd}}^{105}$ has been observed. The reduced radiative lifetimes of the five $E3$ isomers now known in odd-$A$ silver isotopes are compared and found to be constant within a factor of 2.

Measurements of the nuclear spin of206Tl, the hyperfine structure splitting of66Cu, and the nuclear magnetic moments of108Ag(2.3 min) and110Ag(24s)

By using atomic beam magnetic resonance techniques it has been shown that the nuclear spin of 206Tl (half-life 4.2 min) is either zero, or else the nuclear magnetic moment mu I<10-5 nuclear magnetons. Measurements on isotopes of copper and silver have yielded the values for their nuclear spins I and hyperfine interaction constants A, from which their nuclear magnetic moments have been deduced using the Fermi-Segre relation. No diamagnetic correction has been applied.

Gamma-ray investigation of different silver isotope decay

The investigation of different silver isotope decay gamma-rays fromA=102 toA=113 was made using two Ge(Li) detectors with resolution 3·7–6 keV. The results obtained and data from other papers were analyzed to correct and to complete the decay schemes of these nuclei. The radioactivity having a half-time of 3 min. is considered as a new isotope of97Ag. Three new states were added to the level scheme of102Ag in agreement with the results of the Β-gamma and gamma-gamma coincidences. Two gamma-ray transitions were added to the scheme of excited levels of103Pd. About 60 transitions were found in the decay of the two known isomers of104Ag. Most of them are located in the decay scheme of the 19 excited levels of the104Pd isotope. Positive parity was assigned to all of them.

Decay characteristics of short-lived radio-nuclides studied by on-line isotope separator techniques

Short-lived isotopes of argon, krypton, silver, cadmium, tin, iodine, xenon, platinum, gold, mercury, polonium, radon and francium have been studied by the on-line isotope separator technique. Nuclear decey data are presented.

The influence of a self-energy term in nuclear pairing calculations

The influence of a term Σ ν F ν V ν 4 in a conventional BCS pairing calculation is investigated. For a large values of F ν we find in a variation calculation new type calculation new types of minimas which roughly correspond to an excitation of a pair out from the Fermi sea. This could explain some irregularities in the nuclear systematics and especially the strange 1 2 gound-state spin of the silver and rhodium isotopes can (at least qualitatively) be understood in this picture.

Core Excitations inAg107,Ag109,In113,In115,Sb121, andSb123Resulting from Inelastic Scattering of 42-MeV Alpha Particles

$\ensuremath{\alpha}$ particles of 42-MeV energy were elastically and inelastically scattered from isotopically enriched targets of $^{113}\mathrm{In}$, $^{115}\mathrm{In}$, $^{107}\mathrm{Ag}$, $^{109}\mathrm{Ag}$, $^{121}\mathrm{Sb}$, and $^{123}\mathrm{Sb}$. Angular distributions were measured for a number of states in each isotope for angles between 30\ifmmode^\circ\else\textdegree\fi{} and 80\ifmmode^\circ\else\textdegree\fi{}. The results are compared with the predictions of the simple excited-core model with respect to the strengths and energies of the excitations. In all six isotopes, states were found which accounted for all of the one-quadrupole-phonon vibrational strength observed in the neighboring even-even nuclei. In $^{113}\mathrm{In}$, $^{115}\mathrm{In}$, and $^{121}\mathrm{Sb}$, multiplets of states were seen which contained all of the strength of the octupole vibrational states of the even neighbors. In $^{107}\mathrm{Ag}$ and $^{109}\mathrm{Ag}$, only half of the expected octupole strength was observed. In both silver isotopes, a number of states were seen which have approximately the proper strengths and excitation energies to arise from the coupling of the odd proton to a two-phonon vibrational state of the core.

Decay of 13.5 h 109gPd to levels of 109Ag

The β- and γ-decay of the 13.5 h 109gPd to levels of 109Ag has been studied with the use of Ge(Li) detectors, NaI(Tl) crystals and coincidence equipment. The energies (in keV) and relative intensities of γ-rays observed are: 45(3.6), 88(8900), 104(2.2), 135(3.2), 146(2.7), 311(100), 391(2.5), 413.5(26), 415.2(23), 425(1.8), 448(2.6), 551(1.5), 558(6.2), 602(21.5), 636(27), 647 (65), 702(9.2), 707(4.5), 737(5) and 782(33). Excited states in 109Ag were observed at 88 (41 sec 109Ag), 133, 311, 415.2, 702, 724, 736, 840, 863 and 870 keV. Spin and parity assignments for most of the levels were made on the bases of log ft values and γ-ray branching ratios along with data on Coulomb excitation from previous workers. The levels at 0, 311, 415.2, 702 and 863 keV have negative parity and have previously been observed in Coulomb excitation studies. The positive-parity levels at 133 keV has high spin and is apparently the g 9 2 single-quasi-particle level. The negative-parity levels of the odd-mass silver isotopes are understandable in terms of phonons coupled with the p 1 2 single-quasi-particle. However, properties of the positive-parity levels, particularly the low-lying 7 2 + level are not well explained by current nuclear models.