We report the successful growth of BaFe12O19–BaTiO3 (BaM-BTO) bilayer thin films using pulsed laser deposition, considering different crystallographic textures; BTO on (0001)-BaM and BaM on (100)-BTO. Our study involved the bilayers, the individual ferrite and titanate films, and the targets used in their growth. Raman spectroscopy and X-Ray diffraction were used to examine the structure of BaM-BTO thin films, indicating that there is no formation of impurity phases. The morphological characterization was made by scanning electron microscopy, and the magnetic behaviour was studied using SQUID magnetometry. The spontaneous magnetization, magnetic anisotropy constant, and anisotropy field were determined simultaneously from the magnetic hysteresis loop. In addition, we also studied the influence of different annealing temperatures over the magnetic behaviour of bare BaM and covered with BTO thin film. This allows to discern between the different magnetization reversal processes in bilayer systems, indicating a strong correlation between the anisotropy field and the coercive field, and an unusual linear relation of the anisotropy constant with the spontaneous magnetization. Our results indicate a direct influence of the BTO on the magnetic properties of the BaM phase, which places these composite bilayers as excellent candidates for the development of multifunctional devices.

Highly c-axis oriented crystalline ZnO thin films were deposited onto glass substrates by the pulsed laser deposition technique employing a Nd:YAG laser via its second harmonic, and different fluence (0.4...3.2 J/cm(2)) focused on ceramic targets. The influence of the laser fluence on the structure, surface morphology, and optical properties of ZnO films was characterized by X-ray diffraction and Raman spectroscopy, scanning electron microscopy, and transmission UV-IR spectra, respectively. Above the ablation threshold, the laser fluence used is directly linked to the structural defects in the film, thus allowing easy control of the intrinsic stress in the film. Micro-Raman spectra presented vibrational modes, which are assigned to surface phonons modes, indicating the preponderance of nanostructures effects on the films. Our results indicate that the experimental arrangement developed allows the suppression of the superheating effect of the melted target material in the case of visible wavelength lasers irradiations, obtaining films of comparable quality to those obtained by UV-lasers.

 e-mail: zc@famaf.unc.edu.ar La deposición por láser pulsado (PLD por sus siglas en inglés) es una de las técnicas más poderosas para el crecimiento de multicapas delgadas, capaz de conseguir la reproducción estequiométrica de óxidos complejos, además de metales, y polímeros. En este trabajo se presentarán las características principales de un equipo de PLD, diseñado y desarrollado, para la producción de óxidos multicapas de alta calidad, a un costo significativamente inferior a los equipos comerciales actuales. Además, se presentarán algunos de los resultados de los crecimientos de capas de ZnO, y bicapas de BaFe12O19/BaTiO3, estudiados a partir de difracción por rayos X (XRD), microscopía de barrido de electrones (SEM), espectroscopía Raman, y magnetometría SQUID.

This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532 nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydro gels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested. (C) 2016 Elsevier B.V. All rights reserved.

A density functional mPW1PW91 study of the most stable conformers of MOH(H2O)(0-3) clusters (M = alkali or alkaline-earth atom) was performed, along with quantum chemistry CCSD(T,Full) calculations for M = Li and Be. The resulting binding energies for hydration, atom-charge and valence-electron distributions allow for a rationalization of the opposite trends in the cluster-size dependence of adiabatic/vertical ionization energies for the alkali and the alkaline-earth monohydroxides. The closed- and open-shell natures of the latter, respectively, determines their behavior during initial steps of their hydration processes, whereas the ionic/covalent character of their M-OH bonds plays a minor role except for BeOH. (C) 2014 Elsevier B.V. All rights reserved.

The ionization energies (IEe's) of small BaOH(H2O)m clusters (m = 1-3), as generated in a laser vaporization-supersonic expansion source have been determined by laser photoionization experiments over the 3.65-4.55 eV energy range. Complementary ab initio studies show that the IEe's are in good agreement with computed adiabatic ionization energies and that BaOH(H2O)m structures with a direct coordination of the Ba atom to water molecules are favored over those that are characterized by H-bonded networks involving H2O molecules and the OH group of BaOH. Additional calculations have been performed on the hydration energies for the most stable isomers of the relevant BaOH(H2O)1-3 clusters. A comparison is made between the closed-shell title system and the results of related theoretical studies on the open-shell alkali monohydroxides, which allows for an interpretation of the opposite trends that are found in the cluster size dependence of the vertical ionization energies for both series of systems, and highlights the role of the BaOH unpaired electron in its ionization process. Altogether, the present evidence suggests for the initial steps of the BaOH hydration process to be dominated by electrostatic and polarization interactions between the Ba(+) and OH(-) ion cores, which become both increasingly solvated upon sequential addition of water molecules.

Se usó un láser de CO2 TEA construido en el laboratorio, sintonizado en la línea 1 OP(48), 10,91m, para excitar el modo v4 del CDCl3 (914 cm-1). Mediante un filtro gaseoso se aisló la señal de fluorescencia IR emitida por el modo 2v5 del CDCl3 excitado. El análisis de la variación temporal de dicha señal mediante un método de regresión no lineal permitió determinar las constantes de relajación vibracional. Se estudió la dependencia de la relajación V-T de la presión de CDCl3 para una dada fluencia de láser. Se determinó también la dependencia de dicha relajación de la fluencia del láser para una dada presión del CDCl3. Se estudió también la dependencia de la fluencia del láser de la desexcitación del CDCl3 en presencia de gases no reactivos.

The low-energy collisions of I(2)(B,v' = 21) with He involving collision-induced vibrational relaxation of I(2) are investigated both experimentally and by means of wave packet simulations. The theoretical cross sections exhibit a structure of peaks originated by orbiting resonances of the I(2)(B,v' = 21) - He van der Waals complex formed in the I(2) + He collisions. Such a structure has similar characteristics as the structure of peaks found in the experimental cross sections. In fact, four of the five peaks of the measured cross sections appear at positions nearly coincident with those of four of the peaks found in the theoretical cross sections. Thus this result confirms the experimental finding that enhancement of I(2) vibrational relaxation is caused by the population of I(2)(B,v' = 21) - He orbiting resonances populated upon the low-energy collisions. The possibility of using this mechanism in the vibrational cooling of diatomic molecules is discussed.

Resumen en: Our present work is focused in the influence of the oxygen pressure in the growth of Barium Hexaferrite (BaM) films deposited by Pulsed Laser Deposition ...

The H-bonded network rearrangements in the S(0), S(1) and D(0) states of the neutral and cationic p-CreOH(H(2)O)(NH(3)) complexes were studied experimentally by means of (1 + 1)/(1 + 1') REMPI (Resonantly Enhanced MultiPhoton Ionization) and time resolved LIF (Laser Induced Fluorescence) spectroscopies combined with DFT (Density Functional Theory) calculations at the B3LYP/6-311G++(d,p) level. A comparison of the rearrangement process of the H-bonded network in the three states is given. Two cyclic H-bonded isomers were found on the S(0) potential energy surface and the results indicate that the rearrangement in this state is unlikely at the temperature of the supersonic expansion due to the presence of a high-energy barrier (7503 cm(-1)). On the other hand, the re-determination of the S(1) excited state lifetimes confirms that neither the H-bonded rearrangement nor the excited state hydrogen transfer (ESHT) reaction takes place in the S(1) state at the excitation energies of this work. Thus, it is concluded that the absorption of the second photon to reach the D(0) state takes place from the S(1) state of the cyclic-(OH-OH(2)-NH(3)) isomer. A preferential evaporation of H(2)O upon vertical ionization of the cyclic-(OH-OH(2)-NH(3)) isomer is observed which is consistent with a statistical redistribution of the internal energy. Nevertheless, our theoretical calculations suggest that initial excitation of the H-bonded network rearrangement modes may also play a role to leave the H(2)O molecule as a terminal moiety in a chain-(OH-NH(3)-OH(2))(+) isomer. The reaction pathway for the solvent rearrangement involves a double proton transfer process with a very low energy barrier (575 cm(-1)) that is overcome at the vertical ionization energy of the complex.

Physics is the science that studies the interaction between matter and energy. This discipline studies the general properties of bodies, the forces that modify the transfer of energy and the interaction between particles. Physics now has many branches, and one of them is the Biomedical Physics. Biomedical Physics in Medicine applies the principles and methods of physics. This will generate new knowledge and progress towards new horizons in the management of certain diseases. Thus the study of radiation led to progress in the field of diagnosis and therapy of some diseases. Radiation it's called all energy that propagates as a wave through space. Radiation can be classified as ionizing radiation (cosmic rays, gamma rays, x-rays) and non-ionizing radiation. The concept of non-ionizing radiation includes ultraviolet (UV), infrared (IR) and others lasers. Non-ionizing radiations are those that radiation interaction with matter does not generate ions due to its energy content is relatively low. Non-ionizing radiation (laser, ultraviolet and infrared) are commonly used in medicine for diagnosis and therapy. However, they have a deleterious effect on organogenesis (organ formation).

Los estudios químicos sobre restos zooarqueológicos se vienen desarrollando con mayor intensidad en las últimas décadas, especialmente aquellos dedicados a la identificación de huellas químicas o diversos tipos de isótopos y sus relaciones. El objetivo de este trabajo es el de presentar dos procedimientos utilizados para la caracterización química de huesos en base a datos espectrométricos obtenidos mediante la técnica LIBS (Laser Induced Breakdown Spectroscopy). El primero denominado Adición Estándar, consiste en un procedimiento destructivo, con un grado de error estimable, mientras que el segundo, Reemplazo de la Matriz Ósea, constituye un método no invasivo y con un grado de error relativamente bajo. Con esto se espera lograr el desarrollo de un corpus metodológico y analítico que permita caracterizar de un modo eficiente y económico las huellas químicas de diverso material arqueofaunístico. En este sentido se intenta lograr una caracterización química de huesos arqueológicos con el fin de dar respuesta a cuestiones relacionadas tanto a la alimentación como a la movilidad de los animales en el pasado.

The adiabatic ionization potential of the BaOH radical, as generated in a laser vaporization-supersonic expansion source has been determined by laser photoionization experiments to be (4.55 ± 0.03) eV. This value supports the three lowest out of seven previous experimental estimates, the former ranging from 4.35 to 4.62 eV. The present result is compared to ab initio calculations, as performed using both quantum chemistry at different levels of theory and density functional theory, and trying several effective core potentials and their accompanying basis sets for Ba. The most satisfactory agreement is obtained for either the adiabatic or vertical ionization potentials that derive from post-Hartree-Fock [MP2 and CCSD(T)] treatments of electron correlation, along with consideration of relativistic effects and extensive basis sets for Ba, in both BaOH and BaOH(+). Such conclusions extend to the results of related calculations on the Ba-OH dissociation energies of BaOH and BaOH(+), which were performed to help in calibrating the present computational study. Bonding in BaOH/BaOH(+), as well as possible sources of discrepancy with previous experimental determinations of the BaOH adiabatic ionization potential are discussed.

An experimental and theoretical study of the photoionization energies (IE's) of Ba(H(2)O)(n) clusters containing up to n = 4 water molecules has been performed. The clusters were generated by a pick-up source combining laser vaporization with pulsed supersonic expansion, and then photoionized by radiation of 272.5-340 nm. The experimentally determined IE(e)'s for n = 1 to 4 are 4.56 ± 0.05, 4.26 ± 0.05, 3.90 ± 0.05 and 3.71 ± 0.05 eV. This cluster size dependence of IE is reproduced within ±0.06 eV employing the mPW1PW91 density-functional and CCSD(T, Full) quantum-chemical methods combined with the 6-311++G(d,p) basis set for the H and O atoms and three different relativistic effective core potentials for Ba atoms. The calculations indicate that the lowest energy hydration structures represent the most relevant contributions to both the vertical and adiabatic ionization energies. Experimental and theoretical evidence correlates with the progressive surface-delocalization of the electron from the hydration cavity around the Ba atom and suggests that the intra-cluster electron transfer is possible even for small aggregates.

.Pulsed Laser Deposition (PLD) is a powerful technique to grow thin films. Oxides, Magnetics and superconducting materials have been obtained by PLD and theirs properties are strongly dependent of deposition parameters. The construction of a simple and cheap PLD system that is suitable for growing various thin films, including magnetic materials, controlling some deposition parameters is presented. The design characteristics and construction are presented for each one of the devices that compose this PLD system. The equipment has the possibility of carrying out films deposition using up to five targets under controlled atmosphere and substrate temperature. The system also allows controlling the cool off sample time after growing up films at high temperatures. A wide range of relative speeds between target and substrate axial rotation can be externally controlled. With the configuration and the dimensions adopted in their construction, a PLD system of great experimental flexibility is achieved, at a very low cost regarding the commercial systems. To evaluate their performance and effectiveness, the deposition characteristics of a BaFe12O19 film on (0001) sapphire substrate is presented.

An experimental and theoretical study on the reactivity of neutral Ba atoms with water clusters has been conducted to unravel the origin of the irregular intensity pattern observed in one-photon ionization mass spectra of a Ba(H(2)O)(n)/BaOH(H(2)O)(n-1) (n = 1-4) cluster distribution, which was generated in a laser vaporization-supersonic expansion source. The most remarkable irregular feature is the finding for n = 1 of a lower intensity for the Ba(+)(H(2)O)(n) peak with respect to that of BaOH(+)(H(2)O)(n-1), which is opposite to the trend for n = 2-4. Rationalization of the data required consideration of a distinct behavior of ground-state and electronically excited state Ba atoms in inelastic and reactive Ba + (H(2)O)(n) encounters that can occur in the cluster source. Within this picture, the generation of Ba(H(2)O)(n) (n > 1) association products results from stabilizing collisions with atoms of the carrier gas, which are favored by intramolecular vibrational redistribution that operates on the corresponding collision intermediates prior to stabilization; the latter is unlikely to occur for Ba + (H(2)O) encounters. Overall, this interpretation is consistent with additional in-source laser excitation and quenching experiments, which aimed to explore qualitatively the effect of perturbing the Ba atom electronic state population distribution on the observed intensity pattern, as well as with the energetics of various possible reactions for the Ba + H(2)O system that derive from high level ab initio calculations.

. The analysis of the USA 2001 income distribution shows that it can be described by at least two main components, which obey the generalized Tsallis statistics with different values of the q parameter. Theoretical calculations using the gas kinetics model with a distributed saving propensity factor and two ensembles reproduce the empirical data and provide further information on the structure of the distribution, which shows a clear stratification. This stratification is amenable to different interpretations, which are analyzed. The distribution function is invariant with the average individual income, which implies that the inequity of the distribution cannot be modified by increasing the total income.

The economic crisis in Argentina around year 2002 provides a unique opportunity for Econophysics studies. The available data on individual income are analyzed to show that they correspond to non stationary states. However, the rather restricted size of the data survey imposes difficulties that must be overcome through a careful analysis, for a reliable use. A new method of data treatment is presented that could be helpful in theoretical studies.

Both fully dispersed unpolarized and polarized chemiluminescence spectra from the Ba(P3)+N2O reaction have been recorded under hyperthermal laser-ablated atomic beam-Maxwellian gas conditions at three specific average collision energies ⟨Ec⟩ in the range of 4.82–7.47 eV. A comprehensive analysis of the whole data series suggests that the A Σ1+→X Σ1+ band system dominates the chemiluminescence. The polarization results revealed that the BaO(A Σ1+) product rotational alignment is insensitive to its vibrational state υ′ at ⟨Ec⟩=4.82 eV but develops into an strong negative correlation between product rotational alignment and υ′ at 7.47 eV. The results are interpreted in terms of a direct mechanism involving a short-range, partial electron transfer from Ba(P3) to N2O which is constrained by the duration of the collision, so that the reaction has a larger probability to occur when the collision time is larger than the time needed for N2O bending. The latter in turn determines that, at any given ⟨Ec⟩, collinear reactive intermediates are preferentially involved when the highest velocity components of the corresponding collision energy distributions are sampled. Moreover, the data at 4.82 eV suggest that a potential barrier to reaction which favors charge transfer to bent N2O at chiefly coplanar geometries is operative for most of the reactive trajectories that sample the lowest velocity components. Such a barrier would arise from the relevant ionic-covalent curve crossings occurring in the repulsive region of the covalent potential Ba(P3)⋯N2O(Σ1+); from this crossing the BaO(A Σ1+) product may be reached through mixings in the exit channel with potential energy surfaces leading most likely to the spin-allowed b Π3 and a Σ3+ products. The variation with increasing ⟨Ec⟩ of both the magnitude of the average BaO(A Σ1+) rotational alignment and the BaO(A Σ1+) rovibrational excitation, as obtained from spectral simulations of the unpolarized chemiluminescence spectra, consistently points to additional dynamic factors, most likely the development of induced repulsive energy release as the major responsible for the angular momentum and energy disposal at the two higher ⟨Ec⟩ studied. The results of a simplified version of the direct interaction with product repulsion-distributed as in photodissociation model do not agree with the observed average product rotational alignments, showing that a more realistic potential energy surface model will be necessary to explain the present results.

The plumes accompanying 1064 nm nanosecond pulsed laser ablation of barium in vacuum at three moderate incident laser fluences in the range of 5.3–10.8 J/cm2 have been studied using both wavelength and time resolved optical emission spectroscopy and time-of-flight laser-induced fluorescence. Neutral atoms and both singly and doubly charged monatomic cations in excited states up to near the corresponding ionization limits are identified in the optical emission spectra. The population distributions of low-lying (≤1.41 eV) “dark” states of Ba atoms measured by laser-induced fluorescence revel that the metastable D3J and D12 abundances in the plume are higher than predictions based on assuming a Boltzmann distribution. The D3J and D12 populations are seen, respectively, to decrease slightly and nearly no vary with raising fluence, which contrasts with the increasing trend that is observed in the ground-state Ba(S10) population. At all fluences, the time-of-flight distributions of the whole dark states and of various of the emitting levels are bimodal and well described by Maxwell–Boltzmann and shifted Maxwell–Boltzmann velocity functions, respectively, with different average translational temperatures ⟨T⟩ for each state. The ⟨T⟩ values for the dark states are insensitive to the fluence, while for all emitting species marked variations of ⟨T⟩ with fluence are found. These observations have been rationalized in terms of material ejection from the target being dominated by a phase explosion mechanism, which is the main contributor to the Ba(S10) population. Thermionic emission from the target surface can also release initial densities of free electrons and cations which, at the prevailing irradiances, will arguably interact with the incident laser radiation by inverse bremsstrahlung, leading to further excitation and ionization of the various plume species. Such a heating mechanism ensures that the energy injected to the plume will alter the propagation velocities of the primary inverse bremsstrahlung absorbers, i.e., cations, to a major extent than those of neutral atoms with increasing fluence. Electron-ion recombination occurring early in the plume expansion can lead to the generation of both neutral and ionic species in a manifold of long-lived Rydberg states, from which a radiative cascade will likely ensue. The distinct fluence dependences of the Ba(D3J) and Ba(D12) populations and velocity distributions show up the major complexity that distinguishes their populating mechanisms with respect to the remaining species.