A. Bartos's research while affiliated with Universidad Nacional de La Plata and other places

... The XRD patterns of rare-earth oxides such as La 2 O 3 , Gd 2 O 3 , and Dy 2 O 3 are presented in Fig. 5. It is observed [57]; cubic structure with Ia-3 (206) [58]; and cubic structure having space group, Ia-3 (206) [59], respectively. The refined lattice parameters and D values for these oxides are given in Table 4. ...

... This experimental method is useful to determine the temperature dependence of the EFG because its sensitivity is temperature independent, a great advantage that other hyperfine techniques do not present. In many binary oxides studied with the ( 111 In →) 111 Cd TDPAC probe, challenging time-dependent HFIs were sometimes observed and attributed to the so-called aftereffects (AE) phenomenon after the electron-capture (EC) decay of the parent of the 111 In probe (ECAE) [7][8][9][10][11][12][13][14][15][16][17]. It is well known that the EC creates many electronic holes at the 111 Cd atom through Auger processes, almost all of them diffusing fast enough (in less than picoseconds) in such a way that this dynamic effect is not seen by the time window of the TDPAC measurement. ...

... takes into account the Gaussian and Lorentzian time resolution broadening [32,33]. More detailed description of the PAC method can be found at [31,[34][35][36]. ...

... These values are in accordance with previous studies of PAC measurements in Gd 2 O 3 bulk. 19 Results obtained with EMF show that about 18% of the probe nucleus occupy the site that presents νQ=147 MHz, η=0, δ=1.4%. The total hyperfine magnetic field (B hf (total)) presented is a sum of B hf in the sample and the EMF intensity, thus, B hf (total)=B hf (sample)+B(EMF). ...

... The second principal motivation of this combined study arises from the controversial EFG characterization and its theoretical prediction from first principles at substitutional 111 Cd sites in SnO. Results were reported by Rentería et al. [29], performing a series of TDPAC experiments in 111 In(→ 111 Cd)-implanted Sn-O thin films that underwent different thermal treatments in air before each measurement at RT. The authors found that two oxidation states of Sn (2+ and 4+) initially coexisted, related with disordered SnO and SnO 2 phases that were transformed into crystalline SnO 2 by appropriate annealings. ...

... Therefore, a thermal treatment below 1600 K under a pumped vacuum of 10~5 hPa does not reduce any Ti-oxid. Experimentally such a low oxygen activity can be realized by using a controlled gas mixture of CO and C0 2 , as was applied in the PAC studies on CoO, NiO and Cr 2 0 3 [50,72,25,31], As an example, we present results on the REDOX phase transition in manganese oxides obtained by Wiarda and collaborators [48]. The phase transition between the spinel Mn 3 0 4 and the bixbyite Mn 2 0 3 can be driven in both directions without big experimental difficulties. ...

... For 2 Å of inactive In deposition, 23% of probes sense HFI S and 77% sense HFI B , for 7 Å of inactive In deposition around 15% of probes sense HFI S and 85% sense HFI B , i.e., the amount of probes that sense HFI S decreases (and therefore the amount of probes that sense HFI B increases) as the probes are located deeper from the surface. In order to explain the ratio |V S 33 /V B 33 | ≈ 4, the authors performed point-charge-model calculations [39] of the EFG at In atoms in bulk and at the (111) surface of tetragonal In, approximating the complex conduction-electron distribution by point charges centered in the faces of the Wigner-Seitz polyhedra. They studied the EFG on the pure indium system (i.e., not on Cd-doped In), in order to avoid impurity problems (such as unknown structural relaxations and the EFG contribution generated by the Cd electronic shells themselves) and they were only interested in the prediction of this EFG ratio. ...

... The nuclear level that decays emitting γ 1 , τ 1/2 (γ 1 ) = 0.12 ns, in [ 111 In (EC) →] 111 Cd meets this criterion [7][8][9][10][11][12][13][14][15][16][17]. It should be noted that the apparent lack of this type of dynamic interaction in 111 In(→ 111 Cd)-doped TiO 2 [56,57] is not completely conclusive. The employment of a silver sample container in Ref. [57] and the sol-gel procedure in Ref. [56] may have nullified its observation. ...

... 14,15 The unit cell of a bixbyite structure contains 48 oxygen and 32 metal atoms sitting on two nonequivalent sites: site 8b (1/4 1/4 1/4) and 24d (x 0 1/4), where x=0.0307(4) for Gd 2 O 3 and x=−0.0325(5) for Er 2 O 3 , Wyckoff positions, where the first site is occupied by 8 metal atoms with D 3d symmetry and the second is occupied by 24 metal atoms with C 2 symmetry. 16 The O 2− are on the 48e (x y z) position, where x=0.3910(5), y=0.0153(5) and z=0.3779(4) for Gd 2 O 3 and x=0.3910(4), y=0.1521(5) and z=0.3786(4) for Er 2 O 3 . ...

... These conditions were necessary due to the very low activity of the implanted samples and the long duration of the experiments in which single crystals have to be used in order to compare an additional observable -the EFG orientation -with the calculations. Following very few previous experiences in the literature ( [4], Pasquevich, private communication, 1988), we chose a BaF 2 -detector set up with fast-fast coincidence logic, home-made in almost all its parts, trying to improve the detector performance and to gain reliability in the discrimination process. In this work we present a general description of the spectrometer, focusing in the design of the BaF 2 scintillators and the development of a versatile routing/coincidence (RC) unit designed to be used with different acquisition-memory-card-based multichannel analyzers (MCA). ...