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Results for “electronic damage”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Electronic damage in S atoms in a native protein crystal induced by an intense X-ray free-electron laser pulse

Current hard X-ray free-electron laser (XFEL) sources can deliver doses to biological macromolecules well exceeding 1 GGy, in timescales of a few tens of femtoseconds. During the pulse, photoionization can reach the point of saturation in which certain atomic species in the sample lose most of their electrons. This electronic radiation damage causes the atomic scattering factors to change, affecting, in particular, the heavy atoms, due to their higher photoabsorption cross sections. Here, it is shown that experimental serial femtosecond crystallography data collected with an extremely bright XFEL source exhibit a reduction of the effective scattering power of the sulfur atoms in a native protein. Quantitative methods are developed to retrieve information on the effective ionization of the damaged atomic species from experimental data, and the implications of utilizing new phasing methods which can take advantage of this localized radiation damage are discussed.

Galli, L.↗
DOE OSTI2019

Inception of electronic damage of matter by photon-driven post-ionization mechanisms

“Probe-before-destroy” methodology permitted diffraction and imaging measurements of intact specimens using ultrabright but highly destructive X-ray free-electron laser (XFEL) pulses. The methodology takes advantage of XFEL pulses ultrashort duration to outrun the destructive nature of the X-rays. Atomic movement, generally on the order of >50 fs, regulates the maximum pulse duration for intact specimen measurements. In this contribution, we report the electronic structure damage of a molecule with ultrashort X-ray pulses under preservation of the atoms' positions. A detailed investigation of the X-ray induced processes revealed that X-ray absorption events in the solvent produce a significant number of solvated electrons within attosecond and femtosecond timescales that are capable of coulombic interactions with the probed molecules. The presented findings show a strong influence on the experimental spectra coming from ionization of the probed atoms' surroundings leading to electronic structure modification much faster than direct absorption of photons. This work calls for consideration of this phenomenon in cases focused on samples embedded in, e.g., solutions or in matrices, which in fact concerns most of the experimental studies.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Low-damage electron beam lithography for nanostructures on Bi 2 Te 3 -class topological insulator thin films

Nanostructured topological insulators (TIs) have the potential to impact a wide array of condensed matter physics topics, ranging from Majorana physics to spintronics. However, the most common TI materials, the Bi 2 Se 3 family, are easily damaged during nanofabrication of devices. In this paper, we show that electron beam lithography performed with a 30 or 50 kV accelerating voltage—common for nanopatterning in academic facilities—damages both nonmagnetic TIs and their magnetically doped counterparts at unacceptable levels. We additionally demonstrate that electron beam lithography with a 10 kV accelerating voltage produces minimal damage detectable through low-temperature electronic transport. In conclusion, although reduced accelerating voltages present challenges in creating fine features, we show that with careful choice of processing parameters, particularly the resist, 100 nm features are reliably achievable.

42 ENGINEERING↗
DOE OSTI2012

Low energy electron induced damage to plasmid DNA pQE30

Low energy electrons (LEEs) are produced in copious amounts by the primary radiation used in radiation therapy. The damage caused to the DNA by these secondary electrons in the energy range 5-22 eV has been studied to understand their possible role in radiation induced damage. Electrons are irradiated on dried films of plasmid DNA (pQE30) and analysed using agarose gel electrophoresis. Single strand breaks (SSBs) induced by LEE to supercoiled plasmid DNA show resonance structures at 7, 12, and 15 eV for low doses and 6, 10, and {approx}18 eV at saturation doses. The present measurements have an overall agreement with the literature that LEEs resonantly induce SSBs in DNA. Resonant peaks in the SSBs induced by LEEs at 7, 12, and 15 eV with the lowest employed dose in the current study are somewhat different from those reported earlier by two groups. The observed differences are perhaps related to the irradiation dose, conditions and the nature of DNA employed, which is further elaborated.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Dissociation path competition of radiolysis ionization-induced molecule damage under electron beam illumination

Radiolysis ionization under electron beam illumination induces dissociation and damage of organic and biological molecules; thus, it is impossible to image the related materials by transmission electron microscopy (TEM). To understand the atomistic mechanism of radiolysis damage, we developed a systematical procedure based on real-time time-dependent density functional theory (rt-TDDFT) for simulating the radiolysis damage processes of molecules; this procedure can describe the ionization cross sections of the electronic states and the fast dissociation processes caused by hot carrier cooling and the Auger decay on deep levels. For the radiolysis damage of C 2 H 6 O 2 , our simulation unexpectedly showed that there is strong competition among three different dissociation paths, including fast dissociation caused by nonadiabatic cooling of the hot carrier; fast dissociation caused by Auger decay, which induces double ionization and Coulomb explosion; and slow dissociation caused by increased kinetic energy. As the energy of the incident electron beam changes, the time scales of these dissociation paths and their relative contributions to the molecule damage change significantly. These simulation results explain the measured mass spectra of the C 2 H 6 O 2 dissociation fragments and also provide clear competition mechanisms for blocking these dissociation paths in the TEM imaging of organic and biological materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Analysis of Radiation Damage in Electronics of Unmanned Aerial and Ground Robotic Platforms - 19470

Gamma ray measurements are important for monitoring of nuclear facilities. Robotic platforms are used to carry radiation detectors and cameras to enable remote sensing and visual surveillance, allowing for the operation in hazardous, hard to reach zones. The prediction of radiation damage in electronic components of robots is vital. The radiation damage analysis was carried out for two robotic platforms exposed to neutron and gamma ray flux: a ground hexapod platform PhantomX (a 'spider robot') and an aerial platform - the DJI S1000+ octocopter. The FLUKA code was used to analyze the displacement per atom values in electronic components of these robots. The packaging of the components and the shielding design was determined to increase the robot's lifetime in areas where radiation dose levels are high. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

The pristine atomic structure of MoS{sub 2} monolayer protected from electron radiation damage by graphene

Materials can, in principle, be imaged at the level of individual atoms with aberration-corrected transmission electron microscopy. However, such resolution can be attained only with very high electron doses. Consequently, radiation damage is often the limiting factor when characterizing sensitive materials. Here, we demonstrate a simple and an effective method to increase the electron radiation tolerance of materials by using graphene as protective coating. This leads to an improvement of three orders of magnitude in the radiation tolerance of monolayer MoS{sub 2}. Further on, we construct samples in different heterostructure configurations to separate the contributions of different radiation damage mechanisms.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Cathodoluminescence-based nanoscopic thermometry in a lanthanide-doped phosphor

Crucial to analyze phenomena as varied as plasmonic hot spots and the spread of cancer in living tissue, nanoscale thermometry is challenging: probes are usually larger than the sample under study, and contact techniques may alter the sample temperature itself. Many photostable nanomaterials whose luminescence is temperature-dependent, such as lanthanide-doped phosphors, have been shown to be good non-contact thermometric sensors when optically excited. Using such nanomaterials, in this work we accomplished the key milestone of enabling far-field thermometry with a spatial resolution that is not diffraction-limited at readout. We explore thermal effects on the cathodoluminescence of lanthanide-doped NaYF$_4$ nanoparticles. Whereas cathodoluminescence from such lanthanide-doped nanomaterials has been previously observed, here we use quantitative features of such emission for the first time towards an application beyond localization. We demonstrate a thermometry scheme that is based on cathodoluminescence lifetime changes as a function of temperature that achieves $\sim$ 30 mK sensitivity in sub-$\mu$m nanoparticle patches. The scheme is robust against spurious effects related to electron beam radiation damage and optical alignment fluctuations. We foresee the potential of single nanoparticles, of sheets of nanoparticles, and also of thin films of lanthanide-doped NaYF$_4$ to yield temperature information via cathodoluminescence changes when in the vicinity of a sample of interest; the phosphor may even protect the sample from direct contact to damaging electron beam radiation. Cathodoluminescence-based thermometry is thus a valuable novel tool towards temperature monitoring at the nanoscale, with broad applications including heat dissipation in miniaturized electronics and biological diagnostics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Towards phasing using high X-ray intensity

X-ray free-electron lasers (XFELs) show great promise for macromolecular structure determination from sub-micrometre-sized crystals, using the emerging method of serial femtosecond crystallography. The extreme brightness of the XFEL radiation can multiply ionize most, if not all, atoms in a protein, causing their scattering factors to change during the pulse, with a preferential `bleaching' of heavy atoms. This paper investigates the effects of electronic damage on experimental data collected from a Gd derivative of lysozyme microcrystals at different X-ray intensities, and the degree of ionization of Gd atoms is quantified from phased difference Fourier maps. In conclusion, a pattern sorting scheme is proposed to maximize the ionization contrast and the way in which the local electronic damage can be used for a new experimental phasing method is discussed.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Low energy secondary electron induced damage of condensed nucleotides

Radiation damage and stimulated desorption of nucleotides 2'-deoxyadenosine 5'-monophosphate (dAMP), adenosine 5'-monophosphate (rAMP), 2'-deoxycytidine 5'-monophosphate (dCMP), and cytidine 5'-monophosphate (rCMP) deposited on Au have been measured using x-rays as both the probe and source of low energy secondary electrons. The fluence dependent behavior of the O-1s, C-1s, and N-1s photoelectron transitions was analyzed to obtain phosphate, sugar, and nucleobase damage cross sections. Although x-ray induced reactions in nucleotides involve both direct ionization and excitation, the observed bonding changes were likely dominated by the inelastic energy-loss channels associated with secondary electron capture and transient negative ion decay. Growth of the integrated peak area for the O-1s component at 531.3 eV, corresponding to cleavage of the C—O—P phosphodiester bond, yielded effective damage cross sections of about 23 Mb and 32 Mb (1 Mb = 10 –18 cm 2 ) for AMP and CMP molecules, respectively. The cross sections for sugar damage, as determined from the decay of the C-1s component at 286.4 eV and the glycosidic carbon at 289.0 eV, were slightly lower (about 20 Mb) and statistically similar for the r- and d- forms of the nucleotides. Here, the C-1s component at 287.6 eV, corresponding to carbons in the nucleobase ring, showed a small initial increase and then decayed slowly, yielding a low damage cross section (~5 Mb). Although there is no statistical difference between the sugar forms, changing the nucleobase from adenine to cytidine has a slight effect on the damage cross section, possibly due to differing electron capture and transfer probabilities.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Heterogeneous clusters as a model system for the study of ionization dynamics within tampered samples

Tampering of a sample with a layer of another material is a promising technique to slow down the expansion dynamics within laser irradiated samples, with sound implications for single-particle diffraction imaging. Ideally, if an imaged object is covered by a layer of another material, during the irradiation this layer will be primarily ionized and will expand fast due to Coulomb repulsion, whereas the object located within the net neutral core will expand more slowly (hydrodynamically). We investigate the details of the electronic damage within the tampered samples during their irradiation with an intense extreme ultraviolet (EUV) pulse. We study heterogeneous clusters composed of noble gas atoms, Xe and Ar, for which chemical-bond effects can be neglected. Using a fully nonequilibrium kinetic equation code, we demonstrate the influence of cluster composition on ionization dynamics; in particular, on the electronic damage. The results are obtained for the wavelength of 32 nm, which is available at the free-electron laser in Hamburg (FLASH) facility, but our conclusions can also have implications for samples with a more complex structure and irradiated at a much shorter wavelength.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Absolute cross section for loss of supercoiled topology induced by 10 eV electrons in highly uniform /DNA/1,3-diaminopropane films deposited on highly ordered pyrolitic graphite

It was recently shown that the affinity of doubly charged, 1-3 diaminopropane (Dap{sup 2+}) for DNA permits the growth on highly ordered pyrolitic graphite (HOPG) substrates, of plasmid DNA films, of known uniform thickness [O. Boulanouar, A. Khatyr, G. Herlem, F. Palmino, L. Sanche, and M. Fromm, J. Phys. Chem. C 115, 21291–21298 (2011)]. Post-irradiation analysis by electrophoresis of such targets confirms that electron impact at 10 eV produces a maximum in the yield of single strand breaks that can be associated with the formation of a DNA{sup −} transient anion. Using a well-adapted deterministic survival model for the variation of electron damage with fluence and film thickness, we have determined an absolute cross section for strand-break damage by 10 eV electrons and inelastic scattering attenuation length in DNA-Dap complex films.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Study of the neutron damage on electronics at the National Ignition Facility

The NIF environment is very complex leading to a large and non trivial radiation background. A shield surrounding the electronics is required to lower the neutron background to less than 1e7 n/cm{sup 2}. Moving electronics to behind the 6 foot-thick target bay wall is the best shield.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗