Pd Nuclei Research Articles

Neutronh11/2band structures of109,111Pdobserved in heavy-ion induced fission

The neutron-rich nuclei ${}^{109,111}\mathrm{Pd}$ have been produced as fission fragments following the fusion reactions ${}^{28,30}\mathrm{Si}+{}^{176}\mathrm{Yb}$ at 145 MeV and studied with the EUROGAM2 array. Two signature branches of a new band built on the $\ensuremath{\nu}{h}_{11/2}$ orbital have been identified in ${}^{109}\mathrm{Pd}$ and the favored signature of the $\ensuremath{\nu}{h}_{11/2}$ band has been observed for the first time in ${}^{111}\mathrm{Pd}.$ The spectroscopic properties as well as the rotational behavior of these bands are characteristic of bands expected for a prolate nuclear shape in this mass region. The effect of blocking of the first ${h}_{11/2}$ quasineutron in the odd-$A$ Pd nuclei supports the interpretation of the first crossing in the yrast bands of ${}^{110,112}\mathrm{Pd}$ as due to a $\ensuremath{\nu}{(h}_{11/2}{)}^{2}$ pair.

New Spectroscopic Information on 98Pd

Neutron deficient (98)pd nuclei were produced in the Cr-50(Ni-58,2p2 alpha)(98) Pd reaction at a beam energy of 261 MeV. A revision and extension of the level structure of (98)pd is proposed. About 40 new transitions have been assigned to, and placed in the level scheme of this nucleus. A sequence of states are candidates for the negative parity 4-quasiparticle states built on the pi g(9/2)(-3)pi p(1/2)(-1) configuration predicted in the framework of the nuclear shell model.

Displacement Deposition of Sn from Fluoride Solutions on Pd Predeposited (100) Si Substrate

Displacement deposition of tin on Si from fluoride solutions results only in small scattered grains on the surface. However, deposition on a Pd predeposited Si substrate greatly increases the amount of deposited tin. Using morphological and chemical surface analysis, we conclude that Sn deposition occurs on the surface of the substrate placed in between the previously deposited Pd grains. Depending on the distribution of the Pd nuclei on the substrate, a complete surface coverage by nanometric particles of metallic tin can be achieved.

IBM-2 calculations of even-even Pd nuclei

Abstract Excitation energies, electromagnetic transition strengths and static moments in even-even Pd nuclei have been described systematically by using the proton-neutron interacting boson model (IBM-2). Parameters are fitted so as to be consistent with microscopic calculations. Mixed symmetry 2 + states have been identified using the M1 transition strength. The F -spin impurity of the first 2 + state is investigated by means of g -factors and M1 transitions. The calculations have been extended to neutron-rich Pd isotopes with A > 116 for which excited states are still not known.

ChemInform Abstract: Pattern Formation of Cu Layer by Photocatalytic Reaction of ZnO Thin Film.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Coexistence of terminating bands and more collective bands in the A ∼ 100 region of nuclei

Nilsson-Strutinsky cranking calculations on A ≥ 100 Ru and Pd nuclei suggest that, contrary to other mass regions, it should be possible to follow the ground state rotational bands to their termination at spins just above I = 30ℏ and then also to observe other bands which terminate at higher spins.

Pattern Formation of Cu Layer by Photocatalytic Reaction of ZnO Thin Film

A new, fully additive‐based, electroless plating process for the formation of fine Cu patterns without using a conventional photoresist has been developed which utilizes a photocatalytic reaction on thin films prepared on ceramic substrates for printed circuit boards. The layer serves both as an adhesive layer and as a photosensitive layer. The Cu patterns could be easily fabricated in an electroless Cu plating bath after Pd nuclei, which act as catalytic sites for the electroless plating, were patterned via an area‐selective photocatalytic reaction. This was achieved by adsorbing Pd(II) onto the surface and selectively exposing the surface with UV light through a photomask. The unexposed regions can be freed of Pd(II) using ethylenediamine, which can form a stable complex with Pd(II). Cu patterns 17 μm wide, with adhesion strengths suitable for practical use, have been achieved on alumina substrates with this electroless plating method.

Changes in the n-p interaction strengths for Pd and Cd nuclei.

Changes in the n-p interaction strengths for Pd and Cd nuclei.

Enhanced adherence of electroless metal deposit on SiO 2 via control of the chemical environment of the Pd seeding layer

Experimental results are presented on the electroless metallization of SiO 2 using the Pd seeding layer obtained by either laser-assisted or thermal decomposition of a Pd acetylacetonate spun-on precursor layer. The processing of the seeding layer in acetic acid results in an enhanced adherence (up to 2 N/mm 2) of the Ni deposit to glass and fused quartz. XPS analysis of the seeding layer shows that processing in the acid removes the two acetylacetonate “wings” left after the decomposition of Pd(acac) 2 around Pd nuclei. Well-adherent Ni and Cu stripes are deposited onto glass and quartz substrates via laser decomposition of a spun-on Pd(acac) 2 layer with 30 μm spatial resolution for a wide range of scanning velocities of the laser beam.

Controlled Mechanical Adhesion of Electroless Cu Patterns

The adhesion of electroless Cu to smooth ceramic substrates is poor. Controlled mechanical adhesion is accomplished by combining standard integrated‐circuit processes with electroless Cu deposition. A Si wafer is covered with a layer and a pattern. To activate the for electroless Cu, Pd nuclei are selectively deposited on the via a displacement reaction in a solution. Simultaneously, the pattern is underetched. Electroless Cu grows around the created anchors only, thus clenching itself to the substrate. Good adherence of large structures can be obtained by dividing them into small lines or squares. Cu lines, 3 μm wide and 1 μm high have been deposited with good adhesion and selectivity

β-decay of 113Rh and the observation of 113mPd : Isomer systematics in odd- A palladium isotopes

Decay of 113Rh to the levels of 113Pd was studied at the IGISOL-facility by means of β-, γ- and conversion-electron spectroscopy. The level scheme of 113Pd was constructed using 33 gamma transitions on the basis of observed γγ-coincidence relations and half-life analysis. A β-decay half-life of (2.80±0.12) s was measured for 113Rh. A new 9 − 2 isomeric state with (0.3 ± 0.1) s half-life and excitation energy 81.3 keV was discovered in 113Pd. This state and the other recently observed low-lying 9 − 2 or 11 − 2 isomeric states in 115,117Pd isotopes are directly populated in proton-induced fission. The decay of these isomers is unusually strongly hindered compared with Weisskopf estimates. Our observation of two strongly hindered M2 transitions in 113,117Pd with hindrance factors of 7600 and 6800, respectively, imply coexistence of nuclear shapes in odd- A Pd nuclei.

Migration and coalescence of Pd carbonyl clusters in zeolite Y

Admission of carbon monoxide to reduced Pd/NaY at room temperature induces substantial migration and coalescence of primary Pd clusters, as evidenced by EXAFS. In samples calcined at TC= 500 °C and reduced at TR= 200 °C, isolated Pd atoms in sodalite cages prevail initially; Pd clusters in supercages with Pd coordination numbers of 2.4 or 4 are generated by the pretreatment programs TC= 250 °C/TR= 200 °C or TC= 500 °C/TR= 350 °C, respectively. In all these cases Pd13 carbonyl clusters prevail after admission of CO at room temperature. The growth of Pd nuclei is rationalized by assuming that, before CO is admitted, bare Pd interacts with the zeolite matrix, e.g. via proton or Na+ bridges linking Pd with cage-wall oxygens. Adsorption of CO weakens this interaction as primary Pd carbonyl clusters are formed. The mobile Pd carbonyl clusters will coalesce in the supercages until further transport is sterically restricted. This process leads to prevailing Pd13 carbonyl clusters at room temperature as the Pd core of 8.2 Å is unable to traverse the 7.5 Å window. At elevated temperatures, e.g. 200 °C, further growth is possible as the supercage windows expand. As a result, Pd40 clusters are formed and completely fill their supercage.

Levels in 99Pd populated by the 96Ru( alpha,n) and (6Li,p2n) reactions.

The structure of $^{99}\mathrm{Pd}$ has been investigated via the $^{96}\mathrm{Ru}$(\ensuremath{\alpha},n) and $^{96}\mathrm{Ru}$${(}^{6}$Li,p2n) reactions in an attempt to populate low- and high-spin levels of this nucleus. Excitation functions and angular distributions of deexcitation \ensuremath{\gamma} rays have been measured to determine the spins of the levels deduced in \ensuremath{\gamma}-\ensuremath{\gamma} coincidence measurements carried out at 18 MeV (\ensuremath{\alpha} particles) and 38 MeV ${(}^{6}$Li particles), respectively. Several new excited levels are found in the present measurements and the results show that the level structure of $^{99}\mathrm{Pd}$ bears a strong resemblance to that of the isotone $^{97}\mathrm{Ru}$. It appears also that $^{99}\mathrm{Pd}$ may fit nicely into the systematics evinced in the heavier odd-A Pd nuclei.

Photochemical nucleation and growth of palladium on titanium dioxide films studied with electron microscopy and quantitative analytical techniques

Transmission electron microscopy (TEM) investigations showed that millisecond UV illumination of thin polycrystalline TiO/sub 2/ films immersed in an aqueous palladium chloride solution caused the deposition of metallic Pd clusters (size range near 1 nm) on the TiO/sub 2/ surface. During prolonged illumination the existing Pd nuclei grew and the nucleation rate decayed to zero. In the steady growth state Pd photodeposition only took place on existing growth centers. These centers grew by repeated three-dimensional nucleation of 2-4-nm Pd clusters. Separate TiO/sub 2/ memory-effect experiments, in which Pd nucleation took place in the dark, showed that at least 10/sup 14/ electrons/cm/sup 2/ can be trapped in states at the TiO/sub 2/ surface. Photodeposited Pd films were found to be porous, with the result that photodeposition continued for long illumination times. The rate of photodeposition decreased in the initial stages and became constant after the deposition of the equivalent of some tens of monolayers. These observations fit the following model of Pd photodeposition. Photogenerated holes are transferred rapidly to the solution causing a negative surface charge. Pd nucleation starts when a critical concentration of electrons is built up at a certain site. During prolonged illumination electrons leave the TiO/sub 2/ surfacemore » at Pd centers while holes react at bare TiO/sub 2/ surface sites. The Pd growth centers serve as potential wells which attract photoelectrons from surrounding areas.« less

Electroless deposition as a means of obtaining ohmic contacts: Au/Pd onto GaAs

Autocatalytic gold deposits onto palladium-activated GaAs substrates, prepared by chemical displacement, have been found to produce good quality ohmic contacts (in the 10 −5 Ω cm 2 range) provided that the Pd layer thickness and the annealing temperature are optimized. Pd plays the role of catalyst for the subsequent autocatalytic gold deposition; but by using thicker Pd films than necessary to fulfil this “chemical” part, this element also plays another prominent role in the metallurgy of the contact. A transmission electron microscopy (TEM) study has been carried out in order to characterize the growth of Pd nuclei on GaAs. The electrical measurements obtained on such alloyed Au/Pd/ n or p-type GaAs contacts are analyzed in term of a graded amorphous/crystalline junction.

Microscopic structure calculations in Ru, Pd and Cd nuclei

Nuclear structure calculations for Ru, Pd and Cd isotopes are performed in a large configuration space by applying the quadrupole-plus-pairing interaction Hamiltonian. It is found the the large deformations in the neutron-rich isotopes are accompanied by a substantial increase in the occupancy of the 0h11/2 neutron orbital. The energy spectra and the B(E2) values in the deformed nuclei are calculated in the variation-after-projection formalism with angular momentum projection and nucleon number conservation in each state. The results of the calculations are in fair agreement with the corresponding experimental data.

Mixed-symmetry states in the neutron-proton interacting boson model

States of mixed proton-neutron symmetry are investigated in different dynamical symmetries of the interacting boson model. We discuss in each of the limits the energy spectrum, the wave functions and the B( M1; 0 1 + → 1 1 + ) values. We also study three classes of transitional nuclei namely the Pd nuclei [ U(5) → O(6)], the Sm nuclei [ U(5) → SU(3)] and the Pt nuclei [ O(6) → SU(3)] with respect to the energy of the lowest non-symmetric J π = 1 +, 3 + levels as well as the M1 and M3 strengths for exciting these levels from the ground state. For 98Pd we compare this calculation with a shell-model calculation. Finally, we adress the problem of the mixing of the non-symmetric J π = 1 + state with nearby hexadecapole (g-boson) configurations.

Evidence for Triaxial Shapes in Even Ru and Pd Nuclei

Theoretical B(E2) values, B(E2) branching ratios and energy levels for even Ru and Pd nuclei have been calculated recently using Boson Expansion Technique and Interacting Boson Model. The results of these calculations are in poor agreement with the experimental values. The asymmetry parameter γ in these nuclei has been found to be \(23.2^{\circ}{\leqslant}\gamma {\leqslant}27^{\circ}\) and as such these nuclei cannot be regarded as deformed in the original sense of Bohr and Mottelson and these nuclei are expected to be triaxial in shape where the asymmetric rotor model is applicable. Therefore, the Asymmetric Rotor Model has been used to explain known B(E2) values, B(E2) branching ratios and low lying energy levels and a much better agreement has been achieved.

Hyperfine magnetic field on Pd in Pd-Fe alloys

The hyperfine field on Pd nuclei in Pd-Fe alloys has been studied using the integral perturbed angular correlation technique (IPAC). Results are given for samples with iron contents from 3 to 60 at.% Fe and the temperature dependence of the hyperfine field is studied for a sample with 10 at.% Fe.

Shell-model description of very neutron-deficient Pd and Cd nuclei

Shell-model calculations with both proton and neutron degrees of freedom, taking the Z = 50, N = 50 core as a doubly closed shell nucleus, have been carried out. Very neutron-deficient Cd and Pd nuclei are treated. For 98Pd and 102Cd, a detailed comparison between experimental data and calculated quantities such as energy spectra, wave functions, B(E2) values and decay rates, has been carried out. The influence on the description of spectra and wave functions of carrying out a highly truncated shell-model calculation in the separate proton and neutron configuration spaces for 98Pd has been studied in detail.