Applications of Free Electron Lasers in Biology and Medicine

The advent of free electron lasers opens up new opportunities to probe the dynamics of ultrafast processes and the structure of matter with unprecedented spatial and temporal resolution. New methods inaccessible with other known types of radiation sources can be developed, resulting in a breakthrough in deep understanding the fundamentals of life as well as in numerous medical and biological applications. In the present work the properties of free electron laser radiation that make the sources excellent for probing biological matter at an arbitrary wavelength, in a wide range of intensities and pulse durations are briefly discussed. A number of biophysical and biomedical applications of the new sources, currently considered among the most promising in the field, are presented

Oxygen and Silicon K-EXAFS in SiO2\text{}_{2}

The aim of this work was to calculate EXAFS (extended X-ray absorption fine structure) profile of the constituent elements for SiO$\text{}_{2}$ in β-quartz and in its amorphous form within a single scattering curved waves approximation. This method extends the EXAFS analysis to lower energies than the plane wave approximation. We have used wave functions for free ions and Pendry's procedure for central atom phase shifts calculation. Our results for Si K-EXAFS were consistent with experiment, whereas a significant deviation from experimental results for O K-EXAFS was observed. Similar EXAFS profiles for β-quartz and amorphous SiO$\text{}_{2}$ were obtained from calculations

Extended X-ray Bremsstrahlung Isochromat Fine Structure of SiO2\text{}_{2}

X-ray bremsstrahlung isochromat of amorphous SiO$\text{}_{2}$ deposited on Si crystal was measured in an energy range up to 250 eV above the threshold. Extended X-ray bremsstrahlung isochromat he structure (EXBIFS) was observed up to 150 eV for SiO$\text{}_{2}$ studied. The Fourier transform of EXBIFS showed two peaks originated from first and second neighbors around silicon and oxygen ions. Model calculations of EXBIFS of amorphous SiO$\text{}_{2}$ were performed in terms of single scattering of spherical waves and compared with experimental results

Photoemission and Inverse Photoemission Studies of SiO2\text{}_{2}

Occupied and unoccupied electron states of amorphous silicon dioxide film supported on Si crystal are studied by using X-ray photoemission and, for the first time, X-ray inverse photoemission (X-ray bremsstrahlung isochromat method). A special care was undertaken to minimize decomposition of silicon oxide during X-ray bremsstrahlung measurements. The experimental spectra are compared with theoretical band structure calculations for amorphous SiO$\text{}_{2}$ from the literature and good overall agreement is found

Applications of Free Electron Lasers in Biology and Medicine

The advent of free electron lasers opens up new opportunities to probe the dynamics of ultrafast processes and the structure of matter with unprecedented spatial and temporal resolution. New methods inaccessible with other known types of radiation sources can be developed, resulting in a breakthrough in deep understanding the fundamentals of life as well as in numerous medical and biological applications. In the present work the properties of free electron laser radiation that make the sources excellent for probing biological matter at an arbitrary wavelength, in a wide range of intensities and pulse durations are briefly discussed. A number of biophysical and biomedical applications of the new sources, currently considered among the most promising in the field, are presented

Applications of Free Electron Lasers in Biology and Medicine

The advent of free electron lasers opens up new opportunities to probe the dynamics of ultrafast processes and the structure of matter with unprecedented spatial and temporal resolution. New methods inaccessible with other known types of radiation sources can be developed, resulting in a breakthrough in deep understanding the fundamentals of life as well as in numerous medical and biological applications. In the present work the properties of free electron laser radiation that make the sources excellent for probing biological matter at an arbitrary wavelength, in a wide range of intensities and pulse durations are briefly discussed. A number of biophysical and biomedical applications of the new sources, currently considered among the most promising in the field, are presented

BIS Study of Silicon Nitride: Experiment and Theory

X-ray bremsstraMiing isochromat spectroscopic (BIS) study of unoccupied electron states in silicon nitride was performed in an extended energy range. The sample was a 3100 Å layer of silicon nitride deposited on a silicon plate. The isochromat photon energy was 5415 eV. The measurement was performed up to about 250 eV above the BIS threshold. A pronounced maximum of the density of electron state at about lOeV and a weak extended structure up to 200eV were observed. Calculations of the BIS intensity in extended energy range have been performed for silicon nitride using a muffin-tin potential approximation, multiple scattering method and partial probabilities of BIS transitions. The main result is that the BIS of silicon nitride is produced mostly at silicon ions and the BIS extended structure forms mainly due to electron scattering by nearest neighbouring nitrogen ions

X-Ray Absorption Studies of Fe73.5\text{}_{73.5}Cu1\text{}_{1}Nb3\text{}_{3}Si15.5\text{}_{15.5}B7\text{}_{7} Amorphous and Nanocrystalline Alloys

The nanocrystalline state of the formally amorphous alloy Fe$\text{}_{73.5}$Cu$\text{}_{1}$Nb$\text{}_{3}$Si$\text{}_{15.5}$B$\text{}_{7}$ is achieved by a heat treatment at temperatures between 500°C and 600°C. The XANES and EXAFS methods were applied for investigation of local structure and chemical bonding around Fe atoms in amorphous and nanocrystalline alloys. The Fe K absorption spectra were measured in the transmission mode at room temperature for Fe$\text{}_{73.5}$Cu$\text{}_{1}$Nb$\text{}_{3}$Si$\text{}_{15.5}$B$\text{}_{7}$ amorphous and nanocrystalline alloys and compared with the spectra for Fe metallic foil and Fe$\text{}_{3}$Si polycrystalline samples

EXAFS analysis of grain boundaries in nanocrystalline Fe85Zr7B6Cu2\mathrm{Fe_{85}Zr_7B_6Cu_2} alloys

Nanocrystalline Fe85Zr7B6Cu2 alloys were obtained from the formerly amorphous Fe85Zr7B6Cu2 alloy by a heat treatment at several temperatures ranging from 480°C to 600°C. The ultrafine nanocrystalline structure of bcc-Fe grains with a grain size of 3–15 nm diameter embedded in an amorphous matrix was established using transmission electron microscopy. X-ray absorption spectra at the Fe K-edge for Fe85Zr7B6Cu2 amorphous and nanocrystalline alloys and metallic Fe foil were measured using synchrotron radiation.Fourier analysis of extended X-ray absorption fine structure (EXAFS) for alloys was performed and two models of grain boundaries in nanocrystalline Fe85Zr7B6Cu2 alloys were proposed. The heat treatment of alloys at temperatures of 480°C and 500°C creates simple boundaries between crystalline grains and amorphous matrix, while the heat treatment at higher temperatures from 540°C to 600°C can produce boundaries in the form of Fe-free interfaces with thickness of about 0.3 nm. A model of an Fe-free interface being a barrier for grain growth can explain the nanocrystallization phenomenon of Fe85Zr7B6Cu2 alloys

Partial Probabilities of X-Ray Bremsstrahlung Transitions

High-energy electrons bombarding a solid produce X-ray bremsstrahlung radiation, which is one of few elementary processes occurring during electron-solid interactions. Photon emission results from electron transition to an unoccupied electron state above the Fermi level. In this work matrix elements of X-ray bremsstrahlung transitions were calculated for solids containing elements from N (Z=7) to Pd (Z=46) and photon energies 1487 eV and 5415 eV. It was found that in the case of light elements the X-ray bremsstrahlung transitions to s-type final states dominate over all other symmetries. It was also shown that X-ray bremsstrahlung transition probabilities increase with decreasing photon energy and increasing atomic number Z. Dependence of X-ray bremsstrahlung transition probabilities on the electron final state energy is also presented in this work