Exponential absorption edge in hydrogenated α-Si films

Optical and photoelectric measurements demonstrate that hydrogenated amorphous silicon prepared by glow discharge decomposition of silane has an exponential optical absorption edge, over the photon energy range 1.4–1.8 eV with a slope of 0.05–0.08 eV. Evidence is presented that the photogeneration efficiency is unity at room temperature and independent of electric field (10²?10⁴ V/cm^?1) and photon energy (1.2–2.2 eV).     

Double charge transfer in H+ + Mg Collisions

The total cross section for the reaction H⁺ + Mg → H^? + Mg⁺⁺ is calculated in the energy range of 10-10 000 eV. The double charge exchange cross section is large, rising to a maximum of 4× 10^?16 cm² at 100 eV.     

Electron impact ionisation cross sections of cis- and trans-diamminedichloridoplatinum(II) and its hydrolysis products

ABSTRACT

We report total electron-impact ionisation cross sections (EICSs) of cisplatin, its hydrolysis products and transplatin in the energy range from threshold to 10?keV using the binary-encounter-Bethe (BEB) and its relativistic variant (RBEB), and the Deutsch-Märk (DM) methods. We find reasonable agreement between all three methods, and we also note that the RBEB and the BEB methods yield very similar (almost identical) results in the considered energy range. For cisplatin, the resulting EICSs yield cross section maxima of 22.09?×?10^?20?m² at 55.4?eV for the DM method and 18.67?×?10^?20?m² at 79.2?eV for the (R)BEB method(s). The EICSs of monoaquated cisplatin yield maxima of 12.54?×?10^?20?m² at 82.8?eV for the DM method and of 9.74?×?10^?20?m² at 106?eV for the (R)BEB method(s), diaquated cisplatin yields maxima of 7.56?×?10^?20?m² at 118.5?eV for the DM method and of 5.77?×?10^?20?m² at 136?eV for the (R)BEB method(s). Molecular geometry does not affect the resulting EICS significantly, which is also reflected in very similar EICSs of the cis- and trans-isomer. Limitations of the work as well as desirable future directions in the research area are discussed.     

Estimation of the energy of the electron-photon component of cosmic rays on the basis of data for Cherenkov light from ultrahigh-energy extensive air showers

The energy fraction E _em/E ₀ dissipated to the electron-photon component of extensive air showers (EASs) for E ₀=10¹⁵?10¹⁹ eV is estimated using data on Cherenkov radiation and charged particles from the Yakutsk EAS array. The results are compared with models with different dissipations to the electron-photon component and with calculations for various primary nuclei. In the energy range 10¹⁵?10¹⁶ eV and 10¹⁸?10¹⁹ eV, the ratio E _em/E ₀ is equal to 77 ± 2 and 88 ± 2, respectively, in agreement with the mixed and proton contents of primary cosmic rays in the former and latter energy ranges, respectively.     

The adsorption of carbon monoxide,ammonia, and wet air on gold

The work functions of gold films which were deposited on glass substrates in UHV were 0.5–0.9 eV higher than the work function of a well-baked gold sheet. The contact potential difference between a film and the sheet was reduced by wet air admitted to both surfaces at room temperature. Carbon monoxide admitted to both surfaces reduced the contact potential difference reversibly at pressures from 1 × 10^? to 2 × 10^?2 torr, and the evidence suggested that most of the change was owing to a reduction in the work function of the gold film. This reduction varied linearly with the gas pressure; it also depended on the temperature; decreasing from 2.8 eV torr^? at 17°C to < 0.25 eV torr^? at 72°C. The results for CO fitted a simple classical model, from which the mean adsorption energy for CO/Au was estimated as 11.3 ± 0.3 kcal mole^?. Ammonia at 17°C caused a similar reduction of work function at much lower pressures, ～ 10^?4 torr, and its adsorption energy was estimated as 13.6 kcal mole^?1. The films and the sheet gold were polycrystalline with their crystal orientations random in two directions, but their {100} planes were preferentially parallel to the exposed surface. The films were rougher than the sheet. The positive surface potentials for CO/Au and NH₃/Au seem to be due either to weakly bound electropositive states, or to their molecules penetrating into the sub-surface region of the film.     

Eine Atomstrahlquelle für überthermische Energien

A Penning ion source has been used to produce a potassium atomic beam of hyperthermal energies. The energy distribution spreads from below 0.3 eV to about 20 eV. At 1 m distance from the source the current density within a 25% energy window at 1 eV is 2 · 10⁶ atoms · sec^?1· mm^?2.     

On EAS spectrum with extremely low content of hadrons in the primary-energy range ∼10<Superscript>14</Superscript>−10<Superscript>15</Superscript> eV

The distribution of energy fluxes of the hadron component of extensive air showers through an ion-ization calorimeter in the primary-energy range ～3 × 10¹³?10¹⁶ eV is considered. Extensive air showers with zero and minimum energy fluxes of the hadron component are selected. It is concluded that the primary-energy range E ₀ ≈ 1 × 10¹⁴?2 × 10¹⁵ eV contains isotropic γ radiation with a spectrum close to bell-shaped, having a maximum near E ₀ ≈ 2.2 × 10¹⁴ eV and an additional peak near E ₀ ≈ 1.6 × 10¹⁵ eV.     

Messung der quasi-elastischen Neutronenstreuung in Glyzerin mit einem hochauflösenden Kristallspektrometer

A new neutron crystal spectrometer with an energy resolution of 6 · 10^?7 eV was installed at the Munich reactor. The high energy resolution is based on the backscattering of neutrons on silicon single crystals. The energy of the neutrons striking the glycerol sample is varied by Doppler shifting. With this spectrometer the quasielastic line broadening in glycerol was investigated at constant momentum transfer (κ=1.4 ± 0.25) Å^?1 as a function of temperature. The diffusion constants deduced from the experiment are in the order of 10^?7 cm²/s to 5 · 10^?9 cm²/s.     

Elektronenpolarisation im Energiebereich unterhalb 50 eV durch Streuung an freien Hg-Atomen

The angular dependence of spin polarizationP(Θ) of electrons elastically scattered by a beam of mercury atoms is measured in a double scattering experiment for electron energies of 45±1 eV; 23±1 eV; 7±1 eV; and 3,5±1 eV. Maximum degree of polarization obtained isP(100°)=0,39±0,07; electron energy 7±1 eV; electron current 10^?12–10^?11 A.     

Optical properties of Tl2In2Se3S layered single crystals

The optical properties of Tl₂In₂Se₃S layered single crystals have been analyzed using transmission and reflection measurements in the wavelength region between 500 and 1100 nm. The optical indirect transitions with a band gap energy of 1.96 eV and direct transitions with a band gap energy of 2.16 eV were determined from analysis of absorption data at room temperature. Dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single-effective-oscillator model. The refractive index dispersion parameters – oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index – were found to be 4.67 eV, 45.35 eV, 1.38 × 10¹⁴ m ^{? 2} and 3.27, respectively. Transmission measurements were also performed in the temperature range 10–300 K. As a result of temperature-dependent transmission measurements, the rate of change in the indirect band gap with temperature, i.e. γ = ?5.6 × 10^?4 eV/K, and the absolute zero value of the band gap energy, E _gi(0) = 2.09 eV, were obtained.     

Hydrogen-plasma etching of hydrogenated amorphous silicon: a study by a combination of spectroscopic ellipsometry and trap-limited diffusion model

The kinetics of etching hydrogenated amorphous silicon by a hydrogen plasma has been studied by in-situ spectroscopic ellipsometry measurements. The formation of a hydrogen-rich sublayer is clearly emphasized. Its thickness increases from 7 to 27?nm when the temperature during the hydrogen-plasma treatment is raised from 100 to 250°C. This effect is interpreted by solving the differential equation for trap-limited hydrogen diffusion through a mobile surface. By assigning the thickness of this sublayer to the mean diffusion distance of hydrogen we determined values of the effective diffusion coefficient of hydrogen higher than 10^?14?cm²s^?1 with an activation energy of 0.22?eV. The density of hydrogen traps is found to decrease from 7.3 × 10¹⁸ to 4.5 × 10¹⁷?cm^?3 as the temperature of the hydrogen treatment increases from 100 to 250°C with an activation energy of 0.43?eV. This effect is interpreted by a thermal equilibrium involving hydrogen transitions between shallow states and hydrogen-trapping sites.     

Laser induced charge transfer from Ni to CO adsorbed on (111) and (110) surfaces

Ni(110) and (111) surfaces covered with up to one monolayer of CO were irradiated with the light of a dye laser in the photon energy range 2.0 to 3.4 eV. Two-photon photoemission was observed when the laser light was focussed. Upon defocussing a signal was measured which did not depend on the potential of the sample and showed a linear intensity dependence. It is caused by electrons transferred from the Ni substrate into adsorbate states. The signal vanishes for photon energies below 2 eV. This shows that the adsorbate state lies at most 2 eV above the fermi level. The lifetime τ of the electrons in the adsorbate states is estimated to be 10^?10 < τ < 10^?7 s. No fluorescence in the photon energy range above 1 eV could be detected.     

Pressure and temperature dependence of Raman scattering and optical absorption in crystalline S4N4

Raman scattering and optical absorption in crystalline S₄N₄ have been measured both as a function of pressure at 295 K and low temperatures. Polarized single crystal Raman data were also obtained as an aid in the assignment of the Raman active phonons. The pressure coefficients of the Raman active external and S-S stretching modes show a discontinuity near 7 kbar indicative of a second order phase change. The optical absorption edge at about 2.5 eV of a sublimed film of S₄N₄ shows red shifts of 1.3 × 10^?5 eV bar^?1 and 6.3 × 10^?4 eV K^?1 with pressure and temperature respectively. In the light of these results, the electronic, vibrational and structural properties of the crystal are discussed.     

Near-thermal energy width of moderated high energy positrons

More than 10^?7 of the positrons emitted by ¹¹C (produced by proton bombardment of boron) emerge from the room-temperature boron target with a low energy (less than 1 eV) and a measured energy width of (0.100+0.010) eV.     

Electron-Impact Fragmentographic Fluorescence Spectroscopy of Ethanol,Acetaldehyde, 1- and 2-Propanol and Acetone

Abstract

Gaseous ethanol, acetaldehyde, 1-propanol, 2-propanol and acetone at pressures of 2 × 10^?5 to 5 × 10^?4 torr were irradiated with electrons of energies 0-1000 eV. The visible-region fluorescence of the excited fragments was then measured. Studies included pressure dependence, electron energy dependence, threshold energy measurements, and excitation curve measurements. The aim of the research was to ascertain if molecules of similar structure could be differentiated by their spectra.     

Pressure dependence of the absorption edge for Cd1-xMnxTe

The effect of pressure on the optical absorption edge of mixed crystals Cd_1-xMn_xTe with different manganese concentrations is reported. The observed absorption edge shifts to higher energy with increasing pressure at a rate of α=7?8×10^?3 eV/kbar and a second order coefficient of β=-4×10^?5 eV/kbar² for x<0.5, to lower energy with increasing pressure at a rate of α=-5.0 ×10^?3 eV/kbar for x?0.5. A phase transition occurs for all the samples studied. The absorption edge of the new phase is outside the wavenumber range of the instrument. The physical origins of different pressure coefficients are discussed in the light of the deformation potentials of energy band states and the hybridization of the Mn²⁺ 3d levels with the p-like states in the valence band.     

Ionic conductivity of solid lithium iodide and its monohydrate

The solid electrolytes LiI, LiI,H₂O and LiI,D₂O have been characterized by ac- and dc-conductivity measurements. LiI exhibits two conductivity regions: an extrinsic below ≈ 180°C and an intrinsic above, with activation energies of 0.43±0.04 eV and 0.81±0.05 eV respectively. The room temperature conductivities of the hydrates LiI,H₂O and LiI,D₂O are 6.6× 10^?6 and 6.1×10^?6 (Ω cm)^?1 respectively. The activation energy for Li-ion motion in LiI,D₂O is 0.66±0.05 eV.     

Electrical conduction mechanism and carrier trapping in β-metal free phthalocyanine single crystals

The dark electrical conductivity of β-metal free phthalocyanine single crystals has been investigated over the temperature range 273–600°K, at a reduced pressure of 10^?7 torr. The results obtained are in accordance with the model proposed by Barbe and Westgate[5] for this material, in which the energy gap between the top of the valence band and the bottom of the conduction band is determined to be 2·00 eV. At temperatures below about 410°K, the conduction process is consistent with the presence of an electron trapping level located 0·32 eV below the conduction band edge, with a density of 7×10¹⁶ cm^?3, and a donor level of density 2×10⁷ cm^?3 at the same energy. Above about 410°K, there is evidence to suggest that the conduction process is intrinsic.     

Vacuum ultraviolet resonance line radiation source from rare gas atoms and ions for UHV photoelectron spectroscopy

A source and differential pumping system for producing high intensity resonance line radiation from rare gas atoms and ions for ultrahigh vacuum (UHV) photoelectron spectroscopy has been developed. Photoelectron count rates from a gold sample, as measured with a double-pass cylindrical mirror analyzer at pass energy 15 eV and 0.10 eV resolution, are ～ 300,000 c s^?1 for the He(I) (21.22 eV) line and ～30000 c s^?1 for the He(II) (40.81 eV) line. The source design is based on the principle of the electrostatic charged particle oscillator and is capable of sustaining discharges over the pressure range 1 to ～ 10^?6 torr. The discharge segment consists of a cylindrical cold cathode surrounding two tungsten rod anodes which are held at high positive potential. Three stages of differential pumping are employed in order that the vacuum in the main spectrometer chamber can be maintained at 2 × 10^?10 torr during operation. The calculated helium flow reaching the main chamber under these conditions is < 101 s^?1. Details of the construction and operating characteristics of the source are presented.     

Study of He bubbles in Al by electron energy loss spectroscopy

High energy electron energy loss spectroscopy (ELS) has been used to study He bubbles in Al, which were obtained by irradiation of He ions or α-particles of energy ranging from 500 eV to 8 keV and fluences 1x10²⁰m^?2 and 5x10²⁰m^?2. ELS reveals surface plasmon losses of the Al cavities as well as pressure shifts of the He-resonance lines as large as 1 eV. This is viewed as evidence for the existence of a so-called super-dense He in the bubbles. ELS is therefore a promising tool for obtaining information on the He pressure within the bubbles.