Ion Energy Transfer Research Articles

Swift heavy ion irradiation induced modification in structural, optical and luminescence properties of Y2O3:Tb3+ nanophosphor

This paper reports on a comparative study on the structural, optical and luminescence properties of Y2O3:Tb3+ nano-phosphor after 150MeV Ni7+ and 120MeV Ag9+ ion beam irradiation at various fluences ranging from 1×1011 to 1×1013ions/cm2. The modifications in the structural, optical and luminescence properties of the nano-phosphor were studied before and after irradiation by using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance (DR) spectroscopy and photoluminescence spectroscopy (PL). The TEM results show the reduction of the particle size from 75nm to 51 and 18nm after ion irradiation with the Ni7+ and Ag9+ ions, respectively. The calculations from XRD data suggest that the particles consisted out of smaller crystallites of 64, 43 and 10nm for the virgin, Ni7+ and Ag9+ irradiated samples, respectively. DR spectra show a blue shift in the absorption band, resulting in an increase in the band gap after ion irradiation. An increase in the intensity of the PL peaks without any shift in the peak positions was observed with the increase in the ion fluence. The relative intensity ratios of the different emissions at 485, 545, 585 and 625nm due to the characteristic transitions for Tb3+ (5D4→7F6, to 5D4→7F55D4→7F4 and 5D4→7F3), however, changed with the ion fluence. The color coordinates of the Y2O3:Tb3+ therefore changed to the deep green light region with the increase in the ion fluence. The magnitude of the effect of the irradiation is greater in the case of the Ag9+ ions than the Ni7+ ions due to the high electronic energy loss of the Ag9+ ions in the nano-phosphors. The results can be correlated on the basis of linear energy transfer of the irradiated ions.

Large energy-loss straggling of swift heavy ions in ultra-thin active silicon layers

Monte Carlo simulations reveal considerable straggling of energy loss by the same ions with the same energy in fully-depleted silicon-on-insulator (FDSOI) devices with ultra-thin sensitive silicon layers down to 2.5 nm. The absolute straggling of deposited energy decreases with decreasing thickness of the active silicon layer. While the relative straggling increases gradually with decreasing thickness of silicon films and exhibits a sharp rise as the thickness of the silicon film descends below a threshold value of 50 nm, with the dispersion of deposited energy ascending above ±10%. Ion species and energy dependence of the energy-loss straggling are also investigated. For a given beam, the dispersion of deposited energy results in large uncertainty on the actual linear energy transfer (LET) of incident ions, and thus single event effect (SEE) responses, which pose great challenges for traditional error rate prediction methods.

Swift heavy ion induced modifications in metal conducting polymer composite films

Au–polyaniline (Au–PANI) thin films were prepared by an electrochemical process. Au–PANI films were irradiated with 100MeV O7+ and 120MeV Ni9+ ion beams with fluences varying from 3×1011ions/cm2 to 3×1012ions/cm2. The effects of heavy ions on the structural, chemical and morphological properties of the composite films were studied by using X-ray diffraction, Raman and scanning electron microscopy techniques. X-ray spectra showed the gradual decrease in the peak intensity after irradiation. The interchain distance, interplanar distance, micro strain, dislocation density and distortion parameters were calculated. The analysis revealed a noticeable changes in these parameters after irradiation for both cases. The results showed the formation of clusters with a porous structure after irradiation. The effect of irradiation was greater in case of 120MeV Ni9+ rather than 100MeV O7+ ions due to their high electronic energy loss in Au–PANI. I–V characteristic measurements were carried out as a function of ion fluence. The results are discussed on the basis of linear energy transfer (LET) of the irradiated ions.

Effects of Li and Au ion beams irradiation on Makrofol-KG

The Makrofol-KG polycarbonate (M-KG PC) films were irradiated with 45 MeV Li+3 and 150 MeV Au+9 ion beams at various fluences ranging from 1010 to 1012 ions/cm2. Structural, chemical, and optical and surface properties were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible, and atomic force microscopy (AFM), respectviely, as a function of ion fluences. UV–visible spectra exhibit a shift toward the higher wavelength regime after irradiation. This shift clearly reflects decrease in the optical band gap after irradiation. The FTIR spectra show a decrease in intensity of the typical bands. The XRD pattern of M-KG PC shows the decreasing intensity of peak with increase in ions fluence, which reflects loss of crystallinity of the films due to ion beam irradiation. AFM shows that the surface becomes rougher after irridation. The magnitude of the effect of irradiation is larger in the case of 150 MeV Au+9 rather than 45 MeV Li+3 ions due to high electronic energy loss of the Au ions in M-KG PC. The results can be discussed on the basis of linear energy transfer of the irradiated ions.

Numerical and experimental investigation of NIR-to-visible energy up-conversion in Er3+-doped sol–gel SiO2 powders

Er-doped SiO2 powders were prepared by a simple and straightforward sol–gel method using tetraethoxysilane and erbium triflate as sources of SiO2 and Er2O3. Excitation with near-infrared 800 and 980 nm light initiated an energy up-conversion process in these materials, which resulted in the emission in the predominantly red and green parts of the spectrum. Laser power dependence of the intensity of the up-converted emission was studied both experimentally and by using a numerical model to understand the up-conversion mechanism. Excited state absorption (ESA) and five unique ion–ion energy transfer up-conversion (ETU) processes between the relevant levels are identified as possible mechanisms for the observed luminescence. The efficient NIR-visible upconversion was observed even at comparatively low powers of 200 mW cm−2.

1880-nm Broadband ASE Generation With Bismuth–Thulium Codoped Fiber

A broadband amplified spontaneous emission (ASE) generation in 1880-nm region is demonstrated by employing a newly developed single-mode Tm-Bi codoped fiber (TBF) in conjunction with 793-nm pumping for the first time. The TBF was obtained by drawing a preform, which was fabricated using a deposition of porous layer by the modified chemical vapor deposition (MCVD) process in conjunction with solution doping technique. The highest Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> concentrations of 0.35 wt.% and 0.9 wt.%, respectively, were successfully achieved to generate ASE centered at 1880-nm region. The ASE peaked at - 47.2 dBm with 3-dB spectral width ranging from 1817 to 1984 nm with 1.0-m-long TBF and 200-mW 793-nm pump power, which was generated due to the transition of thulium ions from <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> to <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> with some assistance from bismuth to thulium ion energy transfer. The use of a secondary pump of 1550 nm is also shown to improve the ASE generation.

DNA and Cellular Effects of Charged Particles

Development of new radiotherapy strategies based on the use of hadrons, as well as reduction of uncertainties associated with radiation health risk during long-term space flights, requires increasing knowledge of the mechanisms underlying the biological effects of charged particles. It is well known that charged particles are more effective in damaging biological systems than photons. This capability has been related to the production of spatially correlated and/or clustered DNA damage, in particular two or more double-strand breaks (DSB) in close proximity or DSB associated with other lesions within a localized DNA region. These kinds of complex damages are rarely induced by photons. They are difficult to repair accurately and are therefore expected to produce severe consequences at the cellular level. This paper provides a review of radiation-induced cellular effects and will discuss the dependence of cell death and mutation induction on the linear energy transfer of various light and heavy ions. This paper will show the inadequacy of a single physical parameter for describing radiation quality, underlining the importance of the characteristics of the track structure at the submicrometer level to determine the biological effects. This paper will give a description of the physical properties of the track structure that can explain the differences in the spatial distributions of DNA damage, in particular DSB, induced by radiation of different qualities. In addition, this paper will show how a combined experimental and theoretical approach based on Monte Carlo simulations can be useful for providing information on the damage distribution at the nanoscale level. It will also emphasize the importance, especially for DNA damage evaluation at low doses, of the more recent functional approaches based on the use of fluorescent antibodies against proteins involved in the cellular processing of DNA damage. Advantages and limitations of the different experimental techniques will be discussed with particular emphasis on the still unsolved problem of the clustered DNA damage resolution. Development of biophysical models aimed to describe the kinetics of the DNA repair process is underway, and it is expected to support the experimental investigation of the mechanisms underlying the cellular radiation response.

Luminescent behavior and energy transfer in homometallic Eu and ion associating Eu–Zn complexes with a pentadentate ligand

Abstract A pentadentate ligand L (2-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenoxy) -N,N-diphenylacetamide) was self-assembled with Eu (NO3)3 or Zn (NO3)2/Eu (NO3)3 to give homometallic complex ([EuL(NO3)3], 1) or ion associating complex ([ZnL(NO3)]2·[Eu(NO3)5]·CH3CN, 2), respectively. The photoluminescent behavior and energy transfer process were studied in the two complexes by excitation in different ways, in which 2 shows Forster energy transfer mechanism.

The effect of the core morphology of Eu(III)-doped nanoparticles on the ion exchange versus energy transfer between Eu(III) in the core and Cu(II) ions at the interface

The report represents the comparative analysis of luminescent properties of Eu(III) complex in colloids of silica-coated and layer-by-layer-fabricated nanoparticles. The diverse morphologies of these nanoparticles greatly affect their photophysical properties. The interfacial binding with d-ions exemplified by Cu(II) and the contributions of the ion exchange and energy transfer processes between Eu(III) ions confined within polymeric coating and Cu(II) ions at the interface of nanoparticles also depend on their morphology. The silica coating of Eu(III) complex does not prevent it from the efficient ion displacement by the interfacial Cu(II) ions, which results in the irreversible quenching of Eu(III)-centered luminescence. The lack of the ion exchange and the predominant energy transfer between Eu(III) ions in the core and interfacial Cu(II) ions are revealed in the colloids of Eu(III) complex reprecipitated from organic to aqueous solution and coated by the layer-by-layer-fabricated polyelectrolyte multilayer. The obtained results represent the synthetic route of the insertion of Cu(II) ions into the polyelectrolyte multilayer fabricated onto Eu(III) complex.

Angular dependences of SiO2 etch rates in C4F6/O2/Ar and C4F6/CH2F2/O2/Ar plasmas

The angular dependences of SiO2 etch rates for C4F6/O2/Ar and C4F6/CH2F2/O2/Ar plasmas were investigated using a Faraday cage system. In the absence of CH2F2, the steady-state fluorocarbon film that formed on the SiO2 surface was thin enough (&amp;lt;10 Å) for ions to penetrate through the film. The normalized etch yield (NEY) curve in this case showed a maximum value of 1.74 at an ion-incident angle of 70°, illustrating that physical sputtering was a major contributor to the SiO2 etching. The addition of CH2F2 to C4F6/O2/Ar plasmas produced thicker and more etch-resistant fluorocarbon films, leading to a decrease in the ion energy transfer depth through the steady-state films. This implies that physical sputtering was suppressed when CH2F2 was present in the plasma, demonstrated by a decrease in the maximum NEY and the ion-incident angle at the maximum NEY.

High electronic excitation induced modifications by 100 MeV O7+ and 150 MeV Ni11+ ions in Makrofol KG polycarbonate film

Makrofol-KG polycarbonate (M-KG PC) films are irradiated with 150MeV Ni11+ and 100MeV O7+ ion beams at various fluences ranging from 1×1011 to 3×1012ions/cm2. We have investigated the effect of irradiation parameters such as energy and ions fluence on optical, structural and chemical properties of the studied polymer, respectively. UV–Visible, Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) spectral studies have been employed in the present investigation. UV–Visible spectra exhibit a shift towards the higher wavelength regime after irradiation. This shift clearly reflects decrease in optical band gap after irradiation. The FTIR spectrum shows a decrease in intensity of the typical bands whereas the formation of new bands indicates the degradation of the polymer after irradiation. The XRD pattern of M-KG PC shows the decreasing intensity of peak positions with increase in ions fluence, which suggests loss of crystallinity of the films due to irradiation. Observed results indicate the formation of disordered system in the irradiated films. Magnitude of effect of irradiation is greater in case of 150MeV Ni11+ rather than 100MeV O7+ ions due to high electronic energy loss of Ni11+ ions in M-KG PC. The results can be correlated on the basis of linear energy transfer (LET) of the irradiated ions.

Wideband Spectrum-Sliced ASE Source Operating at 1900-nm Region Based on a Double-Clad Ytterbium-Sensitized Thulium-Doped Fiber

A wideband spectrum-sliced amplified spontaneous emission (ASE) source operating in 1900-nm region is demonstrated using a newly developed double-clad ytterbium-sensitized thulium-doped fiber (YTF) and a Sagnac loop mirror. The YTF used was drawn from a D-shape preform, which was fabricated using the modified chemical vapor deposition (MCVD) and solution doping technique. The YTF was pumped by a 980-nm multimode laser to generate an ASE at 1900 nm through the transition of thulium ion from 3F4 to 3H6 with the assistance of ytterbium to thulium ion energy transfer. The broadband ASE was spectral sliced by the loop mirror, which was constructed using a 3-dB coupler and a piece of polarization maintaining fiber (PMF). A wideband comb with channel spacing of 3.3 nm and an extinction ratio of 9 dB was achieved with a multimode pump power of 1 W within a wavelength range of more than 300 nm. The center of the comb spectrum was at 1888 nm with peak power of around -53 dBm.

Ytterbium-sensitized thulium-doped f iber laser with a single-mode output operating at 1 900-nm region

A single-mode laser is demonstrated using a newly developed double-clad thulium-ytterbium-doped fiber (TYDF) in a linear cavity formed by two fiber Bragg gratings (FBGs). The YTF used is drawn from a D-shape preform fabricated using the modified chemical vapor deposition and solution doping technique. The laser is operated at 1 901.6 nm via the transition of thulium ions from 3F4 to 3H6 with the assistance of ytterbium to thulium ion energy transfer. The efficiencies of the laser are 0.71% and 0.75% at 927- and 905-nm multimode pumping, respectively. The thresholds of the launched pump power for 927- and 905-nm pumping are 1 314 and 1 458 mW, respectively. A 7-mW output is obtained at a 905-nm pump power of 2 400 mW.

MULTI-fs – A computer code for laser–plasma interaction in the femtosecond regime

The code MULTI-fs is a numerical tool devoted to the study of the interaction of ultrashort sub-picosecond laser pulses with matter in the intensity range from 10 11 to 10 17 W cm −2. Hydrodynamics is solved in one-dimensional geometry together with laser energy deposition and transport by thermal conduction and radiation. In contrast to long nanosecond pulses, short pulses generate steep gradient plasmas with typical scale lengths in the order of the laser wavelength and smaller. Under these conditions, Maxwellʼs equations are solved explicitly to obtain the light field. Concerning laser absorption, two different models for the electron–ion collision frequency are implemented to cover the regime of warm dense matter between high-temperature plasma and solid matter and also interaction with short-wave-length (VUV) light. MULTI-fs code is based on the MULTI radiation-hydrodynamic code [R. Ramis, R. Schmalz, J. Meyer-ter-Vehn, Comp. Phys. Comm. 49 (1988) 475] and most of the original features for the treatment of radiation are maintained. Program summary Program title: MULTI-fs Catalogue identifier: AEKT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEKT_v1_0.html Program obtainable from: CPC Program Library, Queenʼs University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 49 598 No. of bytes in distributed program, including test data, etc.: 443 771 Distribution format: tar.gz Programming language: FORTRAN Computer: PC (32 bits and 64 bits architecture) Operating system: Linux/Unix RAM: 1.6 MiB Classification: 19.13, 21.2 Subprograms used: Cat Id: AECV_v1_0; Title: MULTI2D; Reference: CPC 180 (2009) 977 Nature of problem: One-dimensional interaction of intense ultrashort (sub-picosecond) and ultraintense (up to 10 17 W cm −2) laser beams with matter. Solution method: The hydrodynamic motion coupled to laser propagation and several transport mechanisms is solved in one-dimensional geometry using a fractional step scheme. Fluid motion together with heat diffusion is solved by using an implicit Lagrangian method. Transport by thermal conduction and radiation as well as electron–ion energy transfer are treated in a two-temperature (electron and ion) model covering the wide range from solid state to high temperature plasma. Laser propagation is calculated from the one-dimensional Maxwell equations. Radiation transfer is solved by using the forward-reverse method for a discrete number of frequency groups. Matter properties are interpolated from tables (equations-of-state, ionization, opacities, and emissivities) generated by external codes. An alternative WKB laser deposition package is available to be used for long pulse lasers. Restrictions: The code has been designed for typical conditions prevailing in short pulse (fs–ps time scale) laser–matter interactions at moderate intensities (10 12–10 17 W cm −2). Although a wider range of situations can be treated, extrapolations to regions beyond this design range need special care. Additional comments: A graphical post processor is included in the package. Its use requires the previous installation of code MULTI2D (see “Subprograms used” above). Running time: 4.8 seconds for the example supplied.

Investigation of the surface chemical and electronic states of pyridine-capped CdSe nanocrystal films after plasma treatments using H2, O2, and Ar gases

Surface chemical bonding and the electronic states of pyridine-capped CdSe nanocrystal films were evaluated using x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy before and after plasma treatments using H2, O2, and Ar gases from the viewpoint of studying the effects of surface capping organic molecules and surface oxidation. Surface capping organic molecules could be removed during the plasma treatment due to the chemical reactivity, ion energy transfer, and vacuum UV (VUV) of the plasma gases. With O2 plasma treatment, surface capping organic molecules were effectively removed but substantial oxidation of CdSe occurred during the plasma treatment. The valence band maximum energy (EVBM) of CdSe nanocrystal films mainly depends on the apparent size of pyridine-capped CdSe nanocrystals, which controls the interparticle distance, and also on the oxidation of CdSe nanocrystals. Cd-rich surface in O2 and H2 plasma treatments partially would compensate for the decrease in EVBM. After Ar plasma treatment, the smallest value of EVBM resulted from high VUV photon flux, short wavelength, and ion energy transfer. The surface bonding states of CdSe had a strong influence on the electronic structure with the efficient strip of capping molecules as well as different surface oxidations and surface capping molecule contents.

Dosimetry in heavy ion beams using various detectors

This contribution is focused on the detailed description of the energy transfer of heavy ions to matter. The experiments were performed at the HIMAC facility in Japan in cooperation with NIRS staff. We employed measuring instruments that have been already been proven in this application; we believe that our specific combination of passive and active detectors is advantageous. Our experimental setup includes track-etched detectors (TED), thermoluminescence dosimeters (TLD), and Liulin, a spectrometer that measures energy deposition in silicon.

Enhanced photoluminescence response of Er 3+–Si nanoparticle codoped Al 2O 3 films by controlled synthesis in the nanoscale and thermal processing

Nanostructured Er 3+–Si nanoparticles (NPs) codoped Al 2O 3 films were synthesized by a one step laser based deposition process which allows to form the Si NPs in situ at room temperature, and to control their size and separation with the Er ions in the nanoscale. Two different thermal annealing treatments are studied in order to optimize the photoluminescence (PL) emission: rapid thermal annealing (RTA) at 900 °C during 2 min, and conventional furnace step annealing at different temperatures up to 750 °C for 1 h. After RTA process the films show an important enhancement on the photoluminescence lifetime values which is related to a reduction of the non-radiative decay channels. Nevertheless, the Si NPs to Er ions energy transfer is strongly reduced. In contrast after conventional furnace annealing up to 700 °C, although there is only a moderate increase of the photoluminescence lifetime values, the excitation of Er ions through Si NPs is still active and as a consequence a large enhancement of the photoluminescence intensity with respect to the Er-only doped film is achieved. These different behaviours are most likely related to structural and chemical changes in the Er environment upon the different annealing processes.

Observation of penning ionization in Zr–Ne discharge by optogalvanic effect

The pulsed optogalvanic (OG) effect is used to observe Penning ionization in a Zr–Ne hollow-cathode discharge, which was axially irradiated by a pulsed dye laser pumped by copper vapor laser. The effect of discharge current on the temporal evolution of the OG signal is studied at 588.2, 594.5, 597.6 and 614.3 nm. The double humped temporal profile of the OG signals, corresponding to transitions of neon, and closeness of energy levels between that level of neon (Ne) and excited levels of zirconium (Zr) ions confirmed that Penning type of ionizing energy transfer collisions were taking place in the Zr–Ne discharge at lower discharge currents (≤5 mA). The disappearance of the double humped feature in the temporal profile of the OG signals indicated that the Penning contribution became negligible at higher discharge currents (≥10 mA).

Experimental Linear Energy Transfer of Heavy Ions in Silicon for RADEF Cocktail Species

Experimental linear energy transfer values of heavy ions in silicon are presented with comparison to estimations from different semi empirical codes widely used among the community. This paper completes the experimental LET data for the RADEF cocktail ions in silicon.

SU-FF-T-661: Investigating the Benefits of Stereotactic Light Ion Radiation Therapy for Treating Large Intracranial AVMs

Purpose The majority of complications occur in patients with large AVM volumes being treated with high doses. For large intracranial arteriovenous malformations, the special characteristics of high ionization density light ion beams offer several advantages over photon and proton beams for high dose stereotactic radiation therapy. These include a better depth dose‐distribution in tissue, negligible lateral scattering, a sharper penumbra, a steep dose fall‐off beyond the Bragg peak and a higher probability of vascular response. Material and Methods Peripheral doses and dose volume histograms (DVHs) of large AVMs were collected from different centers. Based on these data and using a maximum likelihood fitting, dose‐response parameters were derived for the Binomial model. A comparison was performed for different radiation modalities taking also into account their radiobiological differences. Results Light ion Bragg peak dose delivery has the precision required for treating very large AVMs, as well as for delivering extremely sharp focused beams to irregular lesions. For stereotactic radiosurgery with light ions, a better angiographic obliteration rate was observed. Furthermore, a lower complication rate and lower white matter necrosis was simultaneously achieved, which composed a more favorable overall clinical outcome. In patients treated by helium ion beams, a sharper dose‐response gradient was observed, which is probably related to a more homogenous radiosensitivity of the AVM nidus to ion beamradiation.Conclusion Based on this study of linear energy transfer of different therapeuticion beams19 (H, He, Li, C), Helium or Lithium ions may be most suitable for AVM's up to 10 cm3 and for larger AVMs Lithium to carbon ions may be more appropriate. The unique physical characteristics of light ion beams are of considerable advantage for the treatment of AVMs located in front of or adjacent to sensitive and functionally important brain structures.