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Self-excited periodic, quasiperiodic and chaotic oscillations have many significant applications in engineering devices and processes. In the present paper a centralized nonlinear controller is proposed to artificially generate and control self-excited periodic, quasiperiodic, chaotic and hyper-chaotic oscillations of required characteristics in a fully-actuated n-DOF spring-mass-damper mechanical system. The analytical relations among the amplitude, frequency and controller parameters for minimum control energy have been obtained using the method of two-time scale. It is shown that the proposed control can generate modal and nonmodal self-excited periodic and quasiperiodic oscillations of desired amplitude and frequency for minimum control energy. The analytical results have been verified numerically with MATLAB SIMULINK. Bifurcation analysis and extensive numerical simulations reveal a region of multistability in the plane of control parameters, where system responses may be periodic, quasiperiodic, chaotic and hyper-chaotic depending on initial conditions. However, it has been shown that the probability of obtaining chaotic and hyper-chaotic oscillations are very high for a wide range of controller parameters. The procedures of controlling the amplitude, frequency and characteristics of chaotic oscillations are also discussed. The results of the present paper is expected to find applications in various macro and micro mechanical systems and applications.

This paper investigates the vibrational resonance and control of the response of a nonlinear tilted cantilever beam under combined multi-harmonic low and high-frequency excitations. The basic system considers the first mode of vibration of a nonlinear tilted beam under parametric and direct base excitation with the frequency components locked in 2:1 ratio. Such a system is susceptible to parametric amplification of resonance, which may be detrimental for structural health in many mechanical systems. The primary objective of the research is to investigate the efficacy of high-frequency excitation in controlling parametric amplification in the system. To the best of the authors' knowledge such a study was not reported previously in the literature. The slow dynamic equations of the system are obtained using the method of direct partition of motion (MDPM), which is then analysed using the harmonic balance method (HBM). It has been shown that the high-frequency base excitation has a considerable influence on the effective damping and stiffness of the system under consideration. The results of the research demonstrate that high-frequency excitation can effectively control the parametric amplification by shifting the resonance curve in the frequency axis and eliminate undesirable bifurcations by increasing the effective damping. The phenomenon of vibrational resonance has been found for certain parameter values in the presence of high-frequency base excitation. Detail parametric studies are performed to reveal the rich nonlinear dynamics of the system, like multiple jumps in response, dual peaks, isolated resonance response (isola), loop formation in frequency response plot, etc. The numerical results reveal that high-frequency excitation transforms chaotic responses into regular periodic responses. Direct numerical simulations are performed in MATLAB SIMULINK to validate the analytical results.

In this work, for the first time, fragmentation and joining of tungsten oxide (WO3) nanorods induced by a broad ion beam are reported. Although at low energy (5 keV) and moderate ion fluence, nanorods fragment into smaller pieces along the length, at higher ion energies (50-100 keV), a contrary process occurs, which leads to the joining of the nanorods. A state-of-the-art ion-solid interaction simulation, namely, TRI3DYN, has been invoked to explore the possible mechanisms that reveal subtle contributions of surface defects, ion-beam mixing, and sputtering. High-resolution electron microscopy, photoluminescence study, and X-ray photoelectron spectroscopy support the observed results and proposed mechanisms. Such modifications have interesting effects on the electrical conductivity of the nanorod assembly. The change in sample color upon ion irradiation from initial white to yellow, light blue, deep blue, light green, and cyan shows an excellent and reversible chromatic response of tungsten oxide nanorods to irradiation. Such a property can be exploited to fabricate radiation sensors. The fragmentation and joining at different energy scales have essential implications in nanodevice fabrication through the bottom-up approach as well as for the development of fusion reactors.

The current study focuses on the investigation of changes in chemical, wetting, and electrical transport properties of graphene oxide film irradiated by low energy (5 keV) nitrogen ions at differen...

Fabrication of device though bottom-up approach and using nanowires as building blocks has received significant attention as one can build flexible electronics which can handle stress better than thin film based device. However successful joining of the nanowires for fabrication of such device remains a challenge till date. While several well researched joining techniques are available for metal based nanowires, the same for ceramic nanowires is scarce at present. In this work we explore ion beam induced formation of heterojunction between two metal oxide nanowires, namely hydrogen titanate (H2Ti3O7) and cuprous oxide (Cu2O). The electron microscopy studies reveal detailed structural modifications at the joining sections. The ion beam modifications are explained using state-of-the-art TRI3DYN simulations, which details about migration of atoms, defects, sputtering, redeposition and atomic mixing between the two nanowires and emphasize that such junction formation is caused mainly due to atomic collisional effects.

Recent developments of heterojunction-based devices through bottom-up approach such as sensors, light-emitters, energy generation and storage have emerged with great interest due to their wide range of operation and application related flexibilities. This work demonstrates how as-grown hydrogen titanate nanotubes (HTNT) bend and wrap on pristine curpous oxide nanowires (CONW) when mixed together. The unique architecture of wrapping followed by junction formation enhances the active surface area and reduces the contact resistance between the adjacent CONW and HTNT. Such a film upon further ion beam irradiation produces a large-scale network of hetero- and homo-junctions. This newly formed thin film surface upon irradiation shows strong water repelling properties and higher electrical conductivity. The wrapping mechanism, bond formation and the change of conductivity are explained using first principles calculations. The ion beam modifications and large-scale joining are predicted by state-of-the-art TRI3DYN simulation, which is based on binary collision approximation and simulated in a Monte Carlo approach. The observed wrapping and heterojunction are expected to provide excellent mechanical strength and flexibility, which are suitable for fabrication of flexible electronic devices.

We report the influence of morphological changes on the process of charge storage for electrode materials based on ${\mathrm{Ti}\mathrm{O}}_{2}$ nanotubes and provide theoretical insights into the electronic properties from density-functional theory (DFT) simulations. ${\mathrm{Ti}\mathrm{O}}_{2}$ nanotubes are synthesized hydrothermally from nanoparticle precursors. Structural characterization analysis reveals excellent phase purity from the XRD peaks and the formation of uniform and homogeneous nanotubes from field-emission SEM images. Interestingly, cyclic voltammetry and charge-discharge measurements demonstrate that these structurally engineered ${\mathrm{Ti}\mathrm{O}}_{2}$ nanotubes exhibit an enhanced specific capacitance of about $1400\phantom{\rule{0.25em}{0ex}}\mathrm{F}\phantom{\rule{0.25em}{0ex}}{\mathrm{g}}^{\ensuremath{-}1}$ compared with $400\phantom{\rule{0.25em}{0ex}}\mathrm{F}\phantom{\rule{0.25em}{0ex}}{\mathrm{g}}^{\ensuremath{-}1}$ for pristine ${\mathrm{Ti}\mathrm{O}}_{2}$ nanoparticles. Employing DFT simulations, we present the electronic and structural properties of the ${\mathrm{Ti}\mathrm{O}}_{2}$ electrode for charge-storage performance. We compute the diffusion barrier of ${\mathrm{K}}^{+}$ ions in the electrolyte ($\mathrm{KOH}$), the accumulated voltage for different ${\mathrm{K}}^{+}$ concentrations, and the quantum capacitance of the ${\mathrm{Ti}\mathrm{O}}_{2}$ surface. A lower diffusion barrier for ${\mathrm{K}}^{+}$ ions and higher accumulated voltage contribute towards a superior charge-storage performance, which supports experimental observations. Hence, detailed experimental and theoretical analyses predict that a larger surface area in the tubular structure, increased number of delocalized carriers, improved conductivity, and enhanced mobility of the electrolytic ions contribute towards a fast and highly reversible electron-transfer process, leading to enhanced charge-storage performance in morphologically engineered ${\mathrm{Ti}\mathrm{O}}_{2}$ nanotube-based electrodes.

Ion beam assisted joining of nanostructured materials is a relatively new field. In particular, ion beam technique has been proven to be worthwhile for joining ceramic nanostructures. However, a large scope is still remaining to study heterojunctions between two dissimilar materials as the process of formation of bonds between two dissimilar materials is still to be understood. In this work we pick up a ceramic oxide and carbon based material to study ion beam joining. Specifically, we for the first time show heterojunction formation between hydrogen titanate nanowire (HTNW) and carbon nanotube (CNT) by the low energy ion beam. In order to understand the mechanism, we have invoked density functional theory and three-dimensional ion–solid interaction simulations. Experimental results are supported by predictions of simulations and suggest that the joining is established through ion beam mixing, surface defects and sputter redeposition at the junction points. The current study enlightens how the defects and sputtered out atoms are involved in the joining process. The chemical bonds between HTNW and CNT are formed only when C vacancy and simultaneously non-lattice O and C were produced during irradiation. The effect of joining on electrical conductivity and surface wetting has also been studied experimentally in this work, which is supported by simulations.

In this work, we have studied low energy argon ion-induced modification of surface wetting property of molybdenum dioxide nanorod mesh. The nanorods were deposited on a conductive silicon substrate using a spin coating process. The coated thin films were irradiated at two different fluences of 5 × 1016 and 1 × 1017 ions cm−2, respectively. With increasing ion doses, the nanorods tend to bend slightly and a kinky structure is observed in a cross-geometry. While the surface of the as-deposited sample is hydrophilic, the irradiated surface alters into hydrophobic. We have analyzed the morphological and structural properties of the surface in detail to realize the initial and altered wetting properties. Furthermore, the dynamical variations in the contact angle on the molybdenum dioxide surfaces are further investigated to understand the interactions between the water droplet, the sample surface, and the atmosphere. We foresee that such altered surfaces can be helpful to fabricate corrosion-resistant devices.

Multi-walled carbon nanotubes (MWCNT) having diameter in the range of 5–30 nm were coated on silicon wafer using spray coating technique. The coated film was irradiated with 5 keV Na+ at a fluence of 1 × 1016 ions·cm−2. A large-scale welding is observed in the post-irradiated nanotube assembly under scanning electron microscope. We have studied dynamic wetting properties of the nanotubes. While the pristine MWCNT shows superhydrophobic nature, the irradiated MWCNT turns into hydrophilic. Our simulation based on iradina and experimental evidences show defect formation in MWCNT due to ion irradiation. We have invoked mechanism based on defect mediated adsorption of water, which plays major role for transition from superhydrophobic to hydrophilic.

Nanotube or nanowire-based supercapacitors are having huge potentials as they offer large device-level energy density and they can withstand significant stress, which is important for building flexible and high-performance storage devices. The present work shows how we can exploit ion beam as a tool to create surface defects and porous structure besides enhancing charge-transfer property and surface area through large-scale joining among hydrogen titanate nanotubes and achieve enhancement of charge storage capacity and energy density. Self-assembled hydrogen titanate nanotubes have been hydrothermally synthesized on oxidized titanium foil and exposed to low energy (5 keV) Ar+ ion-beam at different ion fluences, before detailed electrochemical analyses to validate their charge storage performance. Irradiated hydrogen titanate nanotubes showed exceptional charge storage performance in terms of specific capacitance, which is about 1572 F/g, at a very high mass-normalized-current of 10 A/g. The charge storage performance of irradiated hydrogen titanate nanotubes was found to be superior to the performance recorded for the pristine/unmodified nanotubes. The detailed experimental findings, further corroborated by first-principles calculations, provide clear insights regarding the enhanced charge storage performance in the case of irradiated nanotubes. We have also computed the work function of the material before and after O vacancy. Reduction in work function due to O vacancy supports improved charge storage performance due to irradiation. Factors like the induced oxygen vacancy, pore formation, improved surface area, and enhanced charge-transfer property play significant roles in the high charge storage performance of the irradiated samples. This study further demonstrates the potential of using the ion beam irradiation technique to tune the surface area, conductivity, and storage capacity of the supercapacitor electrode.

ZnO nanowires grown by hydrothermal method were exposed to a beam of 50 keV argon ions at a fluence of \(1\times 10^{16}\) ions/cm\(^{2}\). The surface morphology of the nanowires has been investigated using high resolution electron microscopy. Raman scattering study has been carried out, which shows specific features resulting from argon ion irradiation. The post-irradiated nanowires exhibit high degree of surface roughness of dimension about few nm and tip of each nanowire is sharpened after this irradiation. The combined effect of surface roughening and tip sharpening are expected to enhance the aspect ratio as well as the effective surface-to-volume ratio. We invoked size and curvature dependent sputtering and defect dynamics to explain the observed features. We envisage that such increase of surface area and tip sharpening may enhance applications of these modified ZnO nanowires in the field of catalysis, gas sensing, field emission and photovoltaic.

Perovskite nanowires are known to be strongly interacting with the moisture. In this work, we demonstrate that strontium manganate (SrMnO3) nanowire, an oxide perovskite, which is initially superhydrophilic, becomes a water repellent upon suitable modification by the ion beam. Highly crystalline SrMnO3 nanowires have been synthesized hydrothermally with an average diameter of about 60 nm and possess 4H crystal structure. The nanowires have been systematically irradiated with nitrogen ions at different energies and in a specific range of ion fluence. For low energy (5 keV), and at a relatively high threshold ion fluence, the nanowire surface starts to become hydrophobic, and the hydrophobicity increases with the ion fluence. However, at higher energies (50–100 keV), the sample surface becomes superhydrophobic at relatively low fluence, and beyond this point, the contact angle is almost independent of the ion fluence. Using state-of-the-art TRI3DYN computer-based simulation, and by employing density functional theory based calculations, we have shown that at low ion energy, the defects turn out to be a dominating factor for the samples to become hydrophobic. At higher ion energies, nanowelding and porous structure lead the way to become superhydrophobic.

TiO2 based nanostructures have been widely explored as photoanodes for dye-sensitized solar cells (DSSCs) because of their favourable band gap and corresponding compatibility with various sensitizers (dye molecules). Various morphologies and textures of titanium oxide have been thoroughly investigated to find the best efficiency in DSSCs. In this work, a detailed study of a nanocomposite of titanium dioxide partly derived from hydrogen titanate precursor has been reported. The current structure is realized in order to achieve optimal photogenerated charge carrier transport and reduced charge recombination. Among many combinations of the composites, the best photoanode showed power conversion efficiency (η) of 8.61% and corresponding open circuit voltage was 0.69 V and short circuit current 17.22 mA cm−2. The efficiency enhancement for the nanorod-nanoparticle composite photoanode is explained by structural, optical, and morphological properties and corroborated with electrochemical impedance spectroscopy.

Hydrogen titanate (HT) nanowires have been widely studied for remarkable properties and various potential applications. However, a handful studies are available related to ion beam induced structural changes and influence on wetting behavior of the HT nanowire surface. In this work, we exposed HT nanowires to 5 keV Na+ at an ion fluence of 1×1016 ions.cm-2. Scanning electron microscope shows that at this ion fluence nanowires are bent arbitrarily and they are welded to each other forming an interlinked network structure. Computer simulation shows that ion beam induces defect formation in the nanowires, which plays major role in such structural modifications. An interesting alteration of surface wetting property is observed due to ion irradiation. The hydrophilic pristine surface turns into hydrophobic after ion irradiation.Hydrogen titanate (HT) nanowires have been widely studied for remarkable properties and various potential applications. However, a handful studies are available related to ion beam induced structural changes and influence on wetting behavior of the HT nanowire surface. In this work, we exposed HT nanowires to 5 keV Na+ at an ion fluence of 1×1016 ions.cm-2. Scanning electron microscope shows that at this ion fluence nanowires are bent arbitrarily and they are welded to each other forming an interlinked network structure. Computer simulation shows that ion beam induces defect formation in the nanowires, which plays major role in such structural modifications. An interesting alteration of surface wetting property is observed due to ion irradiation. The hydrophilic pristine surface turns into hydrophobic after ion irradiation.

A three-dimensional (3D) network of interconnected nanowires of functional materials possesses huge potential for device fabrication since it hinders sluggish interfacial charge carrier transport owing to reduced contact resistance. In the present work, the formation of a highly porous 3D interconnected nano-network by Na+ ion irradiation is demonstrated. The mechanism of solid junction formation at very low energy is established using the results obtained from TRI3DYN computer simulation studies. The formation of a 3D interconnected network resulted in a significant improvement in the electrical conduction as compared to that observed for the pristine nanotube mesh. Further, contact angle measurement shows a transition from “superhydrophilic” nature, as observed for pristine nanotubes, to “superhydrophobic” nature for the 3D nano-network. The superhydrophobicity of the 3D nano-network is expected to find application in miniaturized electronic devices, wherein water condensation and related effects such as short-circuits and erroneous signal output can be significantly minimized.

We report the role of pressure dependent growth of micro and nanorod arrays of zinc oxide by an aqueous solution route. Initially, both micro- and nano-ZnO surfaces show hydrophobicity with water contact angles of 140° ± 3° and 130° ± 3°, respectively. We find that the temporal decay in water contact angle is faster in the case of the nanorod surface compared to that of the microrod surface. While for the microrod surface, the small change in contact angle happens due to water droplet evaporation, the significant change in the particular case of the nanorod surface is attributed to the capillary action.

Low energy nitrogen ions are used in this work to manipulate wetting properties of the surface of the array of Cu2O nano-columns, which yields remarkable results. The nano-columnar thin films were grown on a highly conductive silicon surface by a sputter deposition technique. The films were irradiated at two different fluences of 5 × 10(15) and 1 × 10(16) ions per cm(2), respectively. With increasing fluence the shape of column tip changes, columns are bent and porous channels between columns are clogged up. While the surface of the pristine sample is hydrophilic, the irradiated surface turns into hydrophobic but having adhesion properties. We have analysed the structural and chemical properties of the surface in detail to understand the initial and modified wetting properties. Furthermore, the temporal evolutions of different droplet parameters are investigated to realize the interactions between the water droplet, the sample surface and the atmosphere. We envisage that such modified surfaces can be beneficial for transport of a small volume of liquids with minimum loss and spectroscopic studies, where a small amount of water droplet is available for measurements.

Crystalline nanocolumns of copper oxide has been fabricated through oblique angle sputter deposition technique. The columns are exposed to 15 keV Ar+ ion beam at a fluence of 2 × 1016 ions/cm2. Well-separated nanocolumns are welded upon ion irradiation. The tips of the nanocolumns show prominent joining. Furthermore, wetting property measurements are done for both pristine and irradiated sample, which reveals that a transition occurs from hydrophilic to hydrophobic surface upon ion irradiation.

Nanostructured materials are gaining increasing importance due to their unique properties resulting from the high surface to volume ratio and the altered characteristics of the nanoscaled building blocks. The properties of these materials depend strongly on their microstructure and thus can be controlled by inducing transformation on the nanoscale. In this work, a simple low energy ion beam irradiation technique is presented that can be used to effectively weld the hydrogen titanate nanotubes into a large-scale network of nanowires. By varying the ion fluence, we are able to fragment the entire nanowire network into uniformly distributed nanocrystalline particles with an average size of 5 ± 2 nm. Three-dimensional computer simulations of the ion irradiation effects on the nanotubes reproduce most of the experimental findings and thus confirm that the early development of the system is governed by atomic collision processes. Our study demonstrates that the selective use of ion irradiation can transform metal-oxide nanotubes into large-scale welded networks of nanowires and further into nanocrystalline particles through nucleation and growth.

In this work we report for the first time a method to modify the surface of Cu2O nanowires in a controllable way and physically weld them into a network form, which contributes to higher electrical conductivity as well as a strong water-repelling nature. We have used state-of-the-art theoretical calculations to support our experimental observations. We demonstrate how varying the irradiation fluence can modulate the surface and decorate the nanowire with a uniform distribution of Cu8O nanocrystals due to preferential sputtering. While several well studied joining techniques are available for carbon and metal-based nanowires, the same information for ceramic nanowires is scarce at present. The current study sheds light into this and a state-of-the-art 3D simulation technique predicts most of the modifications including surface modulation, oxygen depletion and welding. The welded network shows higher electrical conductivity than the unwelded assembly. With Cu2O being of p-type the current ion beam joining technique shows a novel path for fabricating p-i-n junctions or solar cell devices through bottom-up approach. Furthermore, we have explored the response of this network to moisture. Our calculation based on density functional theory predicts the hydrophilic nature of individual copper oxide nanowires both before and after irradiation. However, the network shows a strong water-repelling nature, which has been explained quantitatively using the Cassie-Baxter model.

We report the effects of exposing a hydrothermally grown, single crystalline ZnO nanorod array to a beam of 50 keV argon ions at room temperature. High resolution electron microscopy reveals that the ion bombardment results in a nanometer-scale roughening of the nanorod sidewalls, which were almost atomically flat in the pristine sample. Ion bombardment further causes the flat, ≈100 nm diameter nanorod tips to get sharpened to ultrafine points less than 10 nm across. While tip sharpening is attributed to preferential sputtering, the formation of crystalline surface protuberances can be ascribed to surface instability due to curvature dependent sputtering and surface diffusion under argon-ion bombardment. Both the nanoscale roughening as well as the tip sharpening are expected to favorably impact a wide variety of applications, such as those involving catalysis, gas sensing, solar cells, field emission and gas discharge.

We report the results of the x-ray radiative recombination (RR) experiment at the electron cooler of the ESR storage ring performed, for the first time, for detuned (off-cooling) electron energies. In this experiment the recombination of stored, decelerated bare uranium ions with electrons in the energy range 0–1000 meV was studied by observing K-RR x-ray photons emitted from direct radiative recombination to the lowest n=1 state. In this way the RR process was studied in a state selective manner for several off-cooling electron energies. The measured dependency of the recombination rate on the relative electron energies for K-shell RR x-ray photons are compared with the predictions of both nonrelativistic and fully relativistic calculations for the radiative recombination. A role of the relativistic effects, which contribute substantially for higher relative electron energies, are discussed. Strong enhancement of the recombination rate is observed for the the zero relative electron energy (cooling condition) for the K-shell.

Crystalline hydrogen titanate (H2Ti3O7) nanowires were irradiated with N(+) ions of different energies and fluences. Scanning electron microscopy reveals that at relatively lower fluence the nanowires are bent and start to adhere strongly to one another as well as to the silicon substrate. At higher fluence, the nanowires show large-scale welding and form a network of mainly 'X' and 'Y' junctions. Transmission electron microscopy and Raman scattering studies confirm a high degree of amorphization of the nanowire surface after irradiation. We suggest that while ion-irradiation induced defect formation and dangling bonds may lead to chemical bonding between nanowires, the large scale nano-welding and junction network formation can be ascribed to localized surface melting due to heat spike. Our results demonstrate that low energy ion irradiation with suitable choice of fluence may provide an attractive route to the formation and manipulation of large-area nanowire-based devices.

The energy and azimuthal angle dependencies of the asymmetry of spin-polarized low-energy electrons ((00) beam) elastically scattered from a W(110) surface, have been studied before and after irradiated with slow Ar+ ions with energies of 200 eV, 500 eV and 1 keV at a fluence of 5 × 1015 ions/cm2. The energy dependence of the scattered electron asymmetries and intensities (for a fixed azimuthal angle of 55°, which is determined by the angle between the normal to the scattering plane and the [] direction in the surface of the W(110) crystal) and the azimuthal angle dependence of the asymmetry for two different incident electron energies of 14 eV and 23 eV showed a significant change after irradiation. The low-energy ion irradiation influenced the spin-polarized electron scattering more than the higher energy ions. The reason for the change of spin-dependent electron scattering is a quenching of coherent elastic multiple scattering, mainly due to lattice defects induced by implanted ions. Thus, these modifi...

Superheavy quasimolecules are formed transiently during heavy-ion heavy-atom collisions at moderate collision velocities. Using highly charged projectiles, couplings in the inner-most shells of the quasimolecule can be probed. The present investigation of 69 MeV u −1 Bi q + -ions ( q =77, 81 and 82) on thin Au targets was aimed to determine the role of prior-to-collision inner shell vacancy in a superheavy quasiadiabatic collision. The possibility of using very thin solid targets for probing such collisions was investigated and the interaction distances for the inner-shell couplings were calculated.

Charge exchange and X-ray emission for 70 MeV/u highly charged ions of Bi q + [77 ⩽ q ⩽ 82] colliding with thin Au targets [21 ⩽ t in μg/cm 2 ⩽ 225] were measured at the heavy ion synchrotron SIS at GSI. For the innermost shells this beam energy implies a quasiadiabatic collision regime. The charge state distribution of the emerging ions was measured by a position sensitive CVD-diamond detector after being analyzed by a magnet spectrometer. Charge exchange cross sections have been deduced from the target thickness dependence of the charge state distribution. Electron capture at distant collision dominates completely over ionization at close collision. The X-ray emission from the collision partners were measured by solid state detectors, Ge(i). The K X-ray emission for closed and open incoming projectile K vacancies gives access to vacancy transfer in the superheavy quasi-molecule transiently formed during collision for the innermost shells.

Fe-doped ZnO nanorods were synthesized by solvothermal method with Fe concentration of 2%, 5% and 10%, respectively. The morphological and structural properties of the Fe-doped ZnO nanorods were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) technique, respectively. The presence of Fe doping with different concentration was confirmed by X-ray fluorescence (XRF) spectroscopy. For largest doping concentration of Fe, the optical band gap of ZnO was found to shift considerably about 25% to lower energies than that of the pristine ZnO. Furthermore the magnetic behavior was investigated on doped and undoped ZnO samples at room temperature as well as at low temperature. We found that these nanorods do not exhibit room temperature ferromagnetism. Instead a superparamagnetic-type behavior is observed for all the concentration with the blocking temperature in the range 13-35 K.

We study the Bethe binary-encounter (BE) region in the ejected-electron double-differential emission spectrum of ${\mathrm{H}}_{2}$ and He targets in collisions with 8-keV electrons. We compare the absolute cross sections for these isoelectronic systems at high emission energies. The experimental data are analyzed in terms of a state-of-the-art theoretical model based on a two-effective-center approximation. In the case of the ${\mathrm{H}}_{2}$ molecule the binary peak in the double-differential cross sections (DDCS) is enhanced due to the two-center Young-type interference. The observed undulation in the DDCS ratio is explained in terms of the combined contributions of the Compton profile mismatch and the interference effect. The influence of the interference effect is thus observed for higher-energy electrons compared to most of the earlier studies which focused on low-energy electrons produced in soft collisions.

Angular distribution of the $L$ x-ray intensities in Au and Bi induced by 12--55-MeV carbon ions has been measured. The ${L}_{\ensuremath{\alpha}}$, ${L}_{\ensuremath{\beta}}$, and ${L}_{\ensuremath{\gamma}}$ x-ray intensities were found to be isotropic within experimental uncertainty. The alignment parameter ${A}_{20}$ of the ${L}_{3}$ ($2{p}_{3/2}$) subshell was deduced from the measured anisotropy parameter $\ensuremath{\beta}$ value of the well-resolved ${L}_{l}$ line, obtained from the angular distribution of the ${I}_{Ll}/{I}_{L\ensuremath{\alpha}}$, ${I}_{Ll}/{I}_{L\ensuremath{\beta}}$, and ${I}_{Ll}/{I}_{L\ensuremath{\gamma}}$ x-ray intensity ratios. The measured ${A}_{20}$ values have been compared with those obtained using theoretical models that involve the plane-wave Born approximation; projectile's energy loss and its Coulomb deflection from the straight-line trajectory, perturbed-stationary-state, and relativistic effects (ECPSSR); and ECPSSR with the intrashell effect.

Frequency doubling in interference oscillations in fast-ion-induced electron emission spectrum from H2 is investigated. Experimentally observed oscillatory structure is well explained by a model calculation based on the rescattering of emitted electron from the second H center. The second-order contribution is found to be as large as 10%. The doubling of oscillation frequency is found out to be independent of angle of observation. Derived analytical expression for the double differential cross section ratio including the first- and secondorder interference terms, fits the observed oscillatory structure quite well. The present analysis is in broad agreement with the earlier observations by Stolterfoht et al.

The Young-type interference arising due to the spatial coherence has been investigated in the electron emission spectrum from fast electron impact ionization of the inversion symmetric homonuclear diatomic molecule ${\mathrm{H}}_{2}$. The evidence of the interference effect in the angular distribution of the double differential spectrum of the secondary electron is found. The signature of constructive interferences has been identified in the soft-collision regions as well as in binary encounters. The observed oscillation in the forward-backward asymmetry parameter is explained in terms of the Cohen-Fano-type interference coupled with the angular dependence of oscillation frequency. A comparative study indicates a marked difference between the angular asymmetry in the case of fast heavy ion $({\mathrm{F}}^{9+})$ and electron collisions with ${\mathrm{H}}_{2}$ at a similar velocity.