Pd Nuclei Research Articles

Proton hole states in neutron rich Pd nuclei

The ($\stackrel{\ensuremath{\rightarrow}}{t}, \ensuremath{\alpha}$) reaction at 17 MeV triton energy has been used to study proton hole states in targets of $^{106,108,110}\mathrm{Pd}$. The results indicate that for the residual nuclei, $^{105,107,109}\mathrm{Rh}$, the ground states have a spin of ${\frac{7}{2}}^{+}$, in contrast to the lighter Rh nuclei, and are not of single-particle character. Coupled-channels analysis indicates a possible particle-vibration character for these ground states. A strong neutron-proton interaction may be evident from the level systematics of Rh nuclei as the ground state spins change between $N=58$ and $N=60$ ($^{103}\mathrm{Rh}$ and $^{105}\mathrm{Rh}$).NUCLEAR REACTIONS $^{106,108,110}\mathrm{Pd}(\stackrel{\ensuremath{\rightarrow}}{t}, \ensuremath{\alpha})$, $E=17.0$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$, ${A}_{y}$. Deduced levels $^{105,107}\mathrm{Rh}$. DWBA, CCBA analyses.

Nuclear Magnetic Relaxation in Palladium

The Knight shift and the nuclear spin-lattice relaxation rate (1/ T 1 ) of 105 Pd nuclei has been measured in an exchange-enhanced paramagnet Pd metal, in the temperature range between 4.2 and 300 K. Frorn the Knight shift measurement the core polarization hyperfine field is obtained to be -(3.39±0.03)×10 5 Oe/µ B . 1/ T 1 is proportional to temperature with the value, 1/( T 1 T )=1.35±0.03 sec -1 K -1 , below about 150 K, while 1/ T 1 begins to deviate from this relation to smaller values at higher temperature. Relaxation rate due to d-electron spin, (1/ T 1 ) d , was obtained by subtracting the estimated values of other contributions from measured 1/ T 1 . Frorn the value and the temperature dependence of (1/ T 1 ) d , we conclude that (1/ T 1 ) is mostly determined by the long wavelength component of the spin fluctuation in the whole temperature range.

States inAg105,107populated by heavy-ion reactions and interpreted by a quasiparticle-plus-rotor model

Levels in $^{105,107}\mathrm{Ag}$ have been studied using heavy-ion reactions. The experiments included $\ensuremath{\gamma}$-ray yields as a function of bombarding energy, $\ensuremath{\gamma}$-ray angular distributions, and three-detector $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence measurements. The positive-parity band based on the unique-parity ${g}_{\frac{9}{2}}$ orbital in both nuclei exhibits a $\ensuremath{\Delta}I=1$ character, unlike its counterpart ${h}_{\frac{11}{2}}$ band in Pd nuclei. The energy levels, $\ensuremath{\gamma}$-ray mixing ratios, branching ratios, and lifetimes in this band as well as in the ground-state negative-parity band are shown to be in good agreement with calculations using a particle-plus-rotor model at a small, symmetric deformation ($\ensuremath{\delta}=0.12$). The Coriolis and recoil effects are explicitly included and a variable moment of inertia is used. The low-lying "anomalous" $\frac{7}{{2}^{+}}$ state is also readily reproduced by this model. The calculation also shows that the $\ensuremath{\Delta}I=1$ nature of the positive-parity band results primarily from the fact that the Fermi surface is far from the $K=\frac{1}{2}$ state, whereas the transition properties are governed by the Coriolis mixing of the strong-coupled bands. Two bands built on the $\frac{17}{{2}^{\ensuremath{-}}}$ and $\frac{21}{{2}^{+}}$ states with high bandhead energies are thought to have three-quasiparticle configurations.NUCLEAR STRUCTURE $^{92}\mathrm{Zr}$($^{16}\mathrm{O}$,$p2n$)$^{105}\mathrm{Ag}$ at 60 MeV, $^{96}\mathrm{Zr}$($^{14}\mathrm{N}$, $3n$)$^{107}\mathrm{Ag}$ at 49 MeV: measured ${I}_{\ensuremath{\gamma}}(E(^{16}\mathrm{O}))$, ${I}_{\ensuremath{\gamma}}(E(^{14}\mathrm{N}))$, ${I}_{\ensuremath{\gamma}}(\ensuremath{\theta})$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ DCOQ. $^{105,107}\mathrm{Ag}$ deduced levels, $J$, $\ensuremath{\pi}$, $\ensuremath{\gamma}$ mixing ratios. Rotational model calculations, Coriolis, calculated levels, mixing ratios, branching ratios, lifetimes. Ge(Li) detectors.

Decoupled rotational band structure of odd Pd nuclei in a spherical quasiparticle picture

Energy-level calculations are performed for the odd-mass Pd isotopes using a simple model in which valence neutrons in the ${d}_{\frac{5}{2}}$, ${g}_{\frac{7}{2}}$, and ${h}_{\frac{11}{2}}$ orbitals are coupled to a weakly deformed soft core. The softness is simulated by a variable moment-of-inertia representation for the core. A spherical basis is used throughout so that all basis states are eigenstates of good $J$, $R$, and $I$. The Hamiltonian is treated in the BCS approximation, and the deformation for each level is determined by an energy minimization condition. In general, calculated intraband energies are in good agreement with experiment; bandhead positions are much more difficult to fit, especially for $^{105}\mathrm{Pd}$.NUCLEAR STRUCTURE $^{101,\phantom{\rule{0ex}{0ex}}103,\phantom{\rule{0ex}{0ex}}105}\mathrm{Pd}$; calculated levels and deformations. Spherical basis bandmixing calculation with energy minimization with respect to deformation.

Parity determinations inCd105−109from linearly polarized gamma rays following (O16,xn) reactions

The linear polarization of $\ensuremath{\gamma}$ rays from the deexcitation of Cd isotopes $A=105$ through 109 following ($^{16}\mathrm{O},xn$) reactions were measured using a Ge(Li) Compton polarimeter. The linear polarizations are used with $\ensuremath{\gamma}$-ray angular distributions to make unique-parity assignments and to remove ambiguity in angular-momentum values. With these measurements it is possible to identify many states in $^{105\ensuremath{-}109}\mathrm{Cd}$ which are similar to states in Pd nuclei that have been interpreted as having one, two, or three quasiparticles coupled to a slightly deformed rotating core.[NUCLEAR REACTIONS $^{92}\mathrm{Zr}(^{16}\mathrm{O}$, $3n\ensuremath{\gamma})$, $E=58$ MeV; $^{94}\mathrm{Zr}(^{16}\mathrm{O},4n\ensuremath{\gamma})$, $E=63$ MeV; $^{94}\mathrm{Zr}(^{16}\mathrm{O},3n\ensuremath{\gamma})$, $E=59$ MeV; $^{96}\mathrm{Zr}(^{16}\mathrm{O},4n\ensuremath{\gamma})$, $E=56$ MeV; $^{96}\mathrm{Zr}(^{16}\mathrm{O},3n\ensuremath{\gamma})$, $E=56$ MeV. Linear polarization of $^{105\ensuremath{-}106}\mathrm{Cd}$ $\ensuremath{\gamma}$ rays measured.]

Velocity- and Z-dependence of transient magnetic fields in ferromagnetic Gd

The ion-implantation perturbed angular correlation technique (IMPAC) was applied to the study of properties of Gd as stopping material. The transient magnetic fields at Fe, Ge, Mo, Ru, Pd, Cd and Te nuclei implanted into ferromagnetic Gd at 80 K were measured. The static magnetic hyperfine fields for Ru and Pd were deduced to be + 65 ? 25 kG and -45 ? 23 kG, respectively. The Z1-dependence could be fitted by the adjusted Lindhard-Winther theory except for the case of implanted Fe-nuclei. The deviating behaviour for the 56Fe isotope was investigated in a separate experiment, where the dependence of the transient field was found to be directly proportional to the velocity of the recoiling ion. This result is in contradiction to the Lindhard-Winther model.

Velocity- and Z-Dependence of Transient Magnetic Fields in Ferromagnetic Gd

The ion-implantation perturbed angular correlation technique (IMPAC) was applied to the study of properties of Gd as stopping material. The transient magnetic fields at Fe, Ge, Mo, Ru, Pd, Cd and Te nuclei implanted into ferromagnetic Gd at 80 K were measured. The static magnetic hyperfine fields for Ru and Pd were deduced to be + 65 ± 25 kG and -45 ± 23 kG, respectively. The Z1-dependence could be fitted by the adjusted Lindhard-Winther theory except for the case of implanted Fe-nuclei. The deviating behaviour for the 56Fe isotope was investigated in a separate experiment, where the dependence of the transient field was found to be directly proportional to the velocity of the recoiling ion. This result is in contradiction to the Lindhard-Winther model.

Collective and two-quasiparticle excitations inPd102,104,106following (C13,3nγ) reactions

Even-A Pd nuclei were studied using the reactions /sup 92/,/sup 94/,/sup 96/Zr(/sup 13/C,3n..gamma..)/sup 102/,/sup 104/,/sup 106/Pd. The experiments included ..gamma..-ray yield as a function of energy, ..gamma..-ray angular distributions, ..gamma..-ray linear polarizations, and ..gamma..-..gamma.. coincidence measurements. A new treatment of ..gamma..-..gamma.. directional correlation from oriented nuclei, which combines data from all appropriate coincidence pairs to reduce uncertainties, has aided in determining multipolarities for 49 contaminated transitions. Extensive decay schemes are presented which include many high-angular-momentum, positive- and negative-parity states. In addition to the ground-state band, there appear to be three collective bands built on excited two-quasiparticle states. The measurements favor a slightly deformed rotor description of these nuclei over an interpretation in terms of a vibrational (interacting boson) model. (AIP)

Structure calculations for the odd-mass Pd isotopes

The structure of some light, odd-mass Pd isotopes is calculated and compared with experiment. The method uses a renormalized Tabakin potential in a deformed Hartree-Fock calculation, followed by a BCS calculation, to generate deformed quasiparticles. These are then used as input to the band-mixing calculation which yields the spectra of 101,103,105Pd. The interaction parameters and the single particle energies are fixed without reference to data on the Pd isotopes, but the moments of inertia and the core quadrupole moments are taken from experiments on the even Pd nuclei. The occurrence of highly decoupled bands is well-reproduced, including the relative energies of the band heads. The positions and properties of low-lying levels are also correctly predicted, especially in 105Pd for which the experimental data are the most complete.

Pairing factor and band structures in odd-A Pd nuclei

The band structures of the odd-A isotopes 101Pd, 103Pd and 105Pd are discussed in the framework of a core plus particle coupling model. The pairing factor (uj2 − vj2) contained in the effective coiupling strength is found to be responsible for the change of the 52+ ΔJ = 2 band structure observed in 101Pd into a 52+ ΔJ = 1 structure observed in the 103,105Pd nuclei.

Auger studies of electroless nickel films

Auger electron spectroscopy (AES) shows that Pd nuclei obtained by evaporation onto glass are contaminated by S, C and possibly O during air exposure. AES also shows that nickel deposited electrolessly covers such nuclei and that nickel continues to be deposited even when the Pd is completely covered. Apparently both contaminated palladium nuclei and nickel-covered palladium play a catalytic role in electroless deposition of nickel.

Systematic Behavior of Quasirotational Bands in Odd-APd Nuclei

Quasi-rotational bands built on the ${\frac{7}{2}}^{+}$ and ${\frac{11}{2}}^{\ensuremath{-}}$ states in $^{101}\mathrm{Pd}$, $^{103}\mathrm{Pd}$, and $^{105}\mathrm{Pd}$ and the ${\frac{5}{2}}^{+}$ state in $^{101}\mathrm{Pd}$ have been excited by (heavy-ion, $\mathrm{xn}$) reactions. ($d, p$) and ($d, t$) reactions have been used to show that the absence of the ${\frac{5}{2}}^{+}$ band in $^{103}\mathrm{Pd}$ and $^{105}\mathrm{Pd}$ is related to the fragmentation of the ${d}_{\frac{5}{2}}$ quasiparticle strength in these nuclei. An unusual relation has been found between the type of reaction used and the detection of quasirotational bands in odd-$A$ nuclei.

Coriolis-coupling calculation of low-lying states in Ru, Pd and Cd isotopes

The theoretical potential energies and level spectra are reported for odd-mass Ru, Pd and Cd nuclei. The potential energy is calculated by taking into account the blocking effect. The level spectra are obtained by considering a collective and an intrinsic degree of freedom, where the motion of an unpaired quasiparticle in Nilsson's deformed orbital is coupled by a Coriolis force with the rotational motion. For all the nuclei investigated here, the ground state spin-parity and the presence of many even-parity states and of the ccase11 2 − isomeric state are well reproduced by the model. The possible existence of shape isomeric states is suggested.

Average Magnetic Hyperfine Fields atPd106Nuclei in Ni-Pd Alloys

The average magnetic hyperfine fields at $^{106}\mathrm{Pd}$ nuclei in a series of Ni-Pd alloys have been measured at 77 \ifmmode^\circ\else\textdegree\fi{}K by means of the integral perturbed-angular-correlation method using the (622. 0-511. 8)-keV $\ensuremath{\gamma}$-ray cascade in $^{106}\mathrm{Pd}$. The observed magnetic fields have been corrected for the external applied field and the sample magnetization, and extrapolated to 0\ifmmode^\circ\else\textdegree\fi{} K. The average hyperfine fields ${H}_{\mathrm{hf}}$ at the Pd nuclei were found to be negative in the ferromagnetic alloys over the full concentration range, varying from (-194\ifmmode\pm\else\textpm\fi{}9) kG in Ni metal to (-41\ifmmode\pm\else\textpm\fi{}10) kG in an alloy of 90% Pd. Our estimates for the contribution to the hyperfine field of Pd arising from the local moment on the Pd atom are too small to account for the net measured fields. Thus, we ascribe the origin of the remaining large negative fields to interactions with neighboring atoms through the conduction electrons.

Evidence for Local Effects on the Nuclear Spin-Lattice Relaxation Rate in Ferromagnetic Palladium Iron Alloys

For some time there has been considerable theoretical work on the role of local exchange enhancement in highly polarizable systems. To date, there has been little experimental evidence for the importance of these local effects in ferromagnetically polarized alloys. We have measured the nuclear spin-lattice relaxation rate in ferromagnetic PdFe alloys in the helium temperature range. Our results for the Pd nuclei indicate that the relaxation rate is a strong function of the nearest neighbor environment. Specifically there is a contribution to the relaxation rate which is proportional to the number of iron nearest neighbors, N, for N=0, 1, 2 over the concentration range from 1 to 7.5 at.% Fe. Furthermore, the relaxation rates at both the Pd sites and the Fe site vary with concentration as the square of the measured high-field susceptibility. This behavior is consistent with either a strong inter-atomic exchange interaction between a Pd and its nearest neighbors, or a variation in the intra-atomic exchange interaction at a Pd site induced by the change in its nearest-neighbor configuration.

Hyperfine Interactions in Pd3Fe and Pt3Co Alloys

The specific heat of Pd3Fe and Pt3Co Alloys was measured in the temperature interval 0.15°–-1°K at the different degrees of atomic order in the alloys. The constants of magnetic hyperfine interactions were determined by the values of nuclear terms estimated from the total measured specific heat. For the Pd3Fe alloy the values of the effective magnetic field on Pd nuclei were calculated. The increasing of the atomic order degree in the Pd3Fe alloy leads to increase of the absolute value of effective field on Pd. This corresponds to the increase of local magnetic moments of Pd atoms, determined previously by neutron diffraction. In the case of Pt3Co alloy it is very difficult to determine the values of effective magnetic field on Pt and Co separately. The total hyperfine constant due both to Pt and Co vs order degree shows a flat maximum.

Hyperfine Coupling Constants from Specific Heats Down to 0.02°K (Au–Fe and Pd–Fe Dilute Alloys)

We present nuclear specific-heat measurements of dilute Au–Fe and Pd–Fe alloys. The results give integrated information about the hyperfine field induced by the magnetic impurity on the matrix nuclei. In the case of Au, the results are in agreement with the theory. In the case of Pd, an upper bound is given for the number of Pd nuclei affected.

Properties of Excited States of Pd and Cd Nuclei by Coulomb Excitation

We have Coulomb-excited the first-excited (${2}^{+}$) states of most even-even nuclei of Pd and Cd using enriched targets. Three of these states were previously unknown (${\mathrm{Pd}}^{108}$, ${\mathrm{Pd}}^{110}$, and ${\mathrm{Cd}}^{116}$). We also observed excited states in ${\mathrm{Pd}}^{105}$, ${\mathrm{Cd}}^{111}$, and ${\mathrm{Cd}}^{113}$, the latter yielding a new level at 290 kev. Transition probabilities (lifetimes) for these transitions have been determined and show definite systematic trends.