A hyperfine look at titanium dioxide

Titanium dioxide is a commonly used material in a wide range of applications, due to its low price, and the increasing demand for it in the food- and pharmaceutical industries, and for low- and high-tech applications. Time-differential perturbed angular correlation (TDPAC) and Mössbauer spectroscopy measurements have a local character and can provide important and new information on the hyperfine interactions in titanium dioxide. With the application of characterization techniques and radioactive beams, these methods have become very powerful, especially for the determination of temperature dependence of hyperfine parameters, even at elevated temperatures. Such measurements lead to a better understanding of lattice defects and irregularities, including local environments with low fractions of particular defect configurations that affect electric quadrupole interactions. At ISOLDE-CERN, physicists benefit from the many beams available for the investigation of new doping configurations in titanium dioxide. We report the annealing study of titanium dioxide by means of the time differential perturbed γ-γ angular correlation of 111mCd/111Cd in order to study the possible effects of vacancies in hyperfine parameters. This paper also provides an overview of TDPAC measurements and gives future perspectives

Coulomb Excitation of Proton-rich N = 80 Isotones at HIE-ISOLDE

A projectile Coulomb-excitation experiment was performed at the radioactive ion beam facility HIE-ISOLDE at CERN. The radioactive ¹⁴⁰Nd and ¹⁴²Sm ions were post accelerated to the energy of 4.62 MeV/A and impinged on a 1.45 mg/cm²-thin ²⁰⁸Pb target. The γ rays depopulating the Coulomb-excited states were recorded by the HPGe-array MINIBALL. The scattered charged particles were detected by a double-sided silicon strip detector in forward direction. Experimental γ-ray intensities were used for the determination of electromagnetic transition matrix elements. Preliminary results for the reduced transition strength of the B(M1;23+→21+)=0.35(19)μN2 of ¹⁴⁰Nd and a first estimation for ¹⁴²Sm have been deduced using the Coulomb-excitation calculation software GOSIA. The 2³₊ states of ¹⁴⁰Nd and ¹⁴²Sm show indications of being the main fragment of the proton-neutron mixed-symmetry 2⁺₁,ms state

ISOLTRAP setup

The mass spectrometer setup ISOLTRAP@ISOLDE 201

Implementation and commissioning of the phase-imaging ion-cyclotron-resonance method and mass measurements of exotic copper isotopes with ISOLTRAP

An essential component of modern nuclear physics is the description of the composition of the atomic nucleus through experimental and theoretical applications. With only two components, the protons and neutrons, it carries a lot of information which is accessible via its structure. One of these parameters, which can provide information about the structure, is the mass of the atomic nucleus, with which on the basis of the binding energy of the individual constituents, shell-closures, and thus the stability and probabilities of such structures can be explained. Among other things, this information provides the explanation on how elements such as copper, silver and gold can be formed in the first place in a double neutron star merger or in a supernova. This dissertation gives first insights into the new phase-imaging ion-cyclotron-resonance technique at ISOLTRAP, which enables an even higher resolving power of isomeric- and ground-states in a shorter measuring period than with previously used techniques. Thus, this new technique allows to measure more short-lived isotopes than before. The installation as well as the characterization in direct comparison of the old time-of-flight measurement method are evaluated. Furthermore, studies of the electron capture, of the pair $^{202}$Pb-$^{202}$Tl, are presented, with which it is shown whether they can serve the more precise upper neutrino mass limit determination. The high-precision measured masses along the neutron-rich copper isotopes $^{75-79}$Cu, which reach the neutron shell-closure $N$ = 50, are used with their nucleon structure in comparison to a calculation of a shell model to interpret the behavior of the important waiting point nuclide $^{78}$Ni. Finally, the first mass measurements of the isotopes $^{123g,m}$Cd and $^{127g,m}$Cd are presented using the phase imaging method, which were measured at ISOLTRAP and validated with existing values of other facilities. The dissertation concludes with a summary and an outlook on further improvement possibilities of the new phase imaging technique as well as a brief overview of further relevant candidates with respect to mass spectroscopy

Doubly magic Nickel from one proton away

Scientists at CERN’s ISOLDE facility ISOLTRAP have confirmed that nickel-78 is doubly magic by examining its nuclear neighbor, copper-79

Direct decay-energy measurement as a route to the neutrino mass

International audienceA high-precision measurement of the$^{131}$Cs→$^{131}$Xe ground-to-ground-state electron-capture Q$_{EC}$-value was performed using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The novel PI-ICR technique allowed to reach a relative mass precision δm/m of 1.4 ⋅ 10$^{− 9}$. A mass resolving power m/Δm exceeding 1 ⋅ 10$^{7}$ was obtained in only 1s trapping time. Allowed electron-capture transitions with sub-keV or lower decay energies are of high interest for the direct determination of the ν$_{e}$ mass. The new measurement improves the uncertainty on the ground-to-ground-state Q$_{EC}$-value by a factor 25 precluding the$^{131}$Cs→$^{131}$Xe pair as a feasible candidate for the direct determination of the ν$_{e}$ mass

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Work of numerous research groups has shown different outcomes of studies of the transition from the ferroelectric α-phase to the high temperature β-phase of the multiferroic, magnetoelectric perovskite Bismuth Ferrite (BiFeO3 or BFO). Using the perturbed angular correlation (PAC) method with 111mCd as the probe nucleus, the α to β phase transition was characterized. The phase transition temperature, the change of the crystal structure, and its parameters were supervised with measurements at different temperatures using a six detector PAC setup to observe the γ−γ decay of the 111mCd probe nucleus. The temperature dependence of the hyperfine parameters shows a change in coordination of the probe ion, which substitutes for the bismuth site, forecasting the phase transition to β-BFO by either increasing disorder or formation of a polytype transition structure. A visible drop of the quadrupole frequency ω0 at a temperature of about Tc≈820∘C indicates the α−β phase transition. For a given crystal symmetry, the DFT-calculations yield a specific local symmetry and electric field gradient value of the probe ion. The Pbnm (β-BFO) crystal symmetry yields calculated local electric field gradients, which very well match our experimental results. The assumption of other crystal symmetries results in significantly different computed local environments not corresponding to the experiment