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HEBREW UNIV JERUSALEM (Israel) DEPT OF PHYSICS

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Works: 15 works in 18 publications in 1 language and 18 library holdings
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Publications about HEBREW UNIV JERUSALEM (Israel) DEPT OF PHYSICS
Publications by HEBREW UNIV JERUSALEM (Israel) DEPT OF PHYSICS
Most widely held works by HEBREW UNIV JERUSALEM (Israel) DEPT OF PHYSICS
Crystallization in magnetic and electric fields by Michael M Schieber( Book )
2 editions published between 1969 and 1971 in English and held by 2 libraries worldwide
The kinetics of crystal growth on a seed in solutions has been studied for the antiferromagnetic water soluble crystal Cu(CH3000)2H2O I around 1-2C and the rate of growth and dissolution has been investigated for the ferroelectric Rochelle salt crystal NaK C2H4O2(COO)2.4 H2O II around 19 and 24C. The antiferromagnetic Neel point T(N) of I is 7C and the ferroelectric Curie temperature T(c) of II is 24C. The growth of crystals I has been performed also in high magnetic fields up to 142 KOe. Two crystals of I, one outside and the other inside the high magnetic field have been investigated. The Isothermal rate of growth inside the field has been at a temperature about 0.3C higher than outside the field. (Author)
Plasma Propagation into Low-Pressure Gas and Plasma in a Magnetic Field ( Book )
2 editions published between 1970 and 1972 in English and held by 2 libraries worldwide
The report summarizes investigations of plasma phenomena related to the propagation of plasma into an ambient gas. The phenomena are-the solar wind, electro-static containment of an ionized gas, containment in crossed electric and magnetic fields and the positive column in a magnetic field. (Author)
Electron density and ionization phenomena in shock waves ( Book )
2 editions published between 1965 and 1967 in English and held by 2 libraries worldwide
The microwave attenuation of the air of shock waves of well-developed shocks within Mach number 7-12 was measured. The time dependence of the microwave attenuation was also carefully studied. The effect of converging or diverging transition sections was investigated by measuring (a) Changes in the Mach speed (b) Changes in the microwave attenuation (c) Optical light emission. (Author)
Microwave measurements on shock waves in air ( Book )
1 edition published in 1963 in English and held by 1 library worldwide
The microwave attenuation by shock waves in air was investigated in the Mach No. range of 8 - 12 and at pressures 1-5 mm Hg. It is shown that an analysis of the time dependence of the attenuation yields important information regarding (a) the maximum electron-density (b) the build-up of the electron density and the beginning of the shock, (c) the electron density near the contact surface, and (d) the length of the heated slug section. An investigation was made of the effect of transitions from a larger diameter shock tube to a smaller tube on the maximum microwave attention, on its time dependence, and on the Mach No. In particular, a study was made of the effect of shorter and larger taper sections as well as abrupt transitions for various Mach Numbers and initial pressures. (Author)
Optical Measurements and Microwave Measurements Behind Shock Waves ( Book )
1 edition published in 1969 in English and held by 1 library worldwide
Measurements of Mach speed, of optical emission and microwave attenuation on converging and diverging taper sections are reported. A detailed analysis of the shock flow of the transmitted, reflected and re-reflected waves is attempted. A comparison of the data with the various theories is given. (Author)
Degree of ionisation of fe lines in the solar spectrum in the range 170-220 a ( Book )
1 edition published in 1964 in English and held by 1 library worldwide
Radiation Effects on Quartz Crystals and Oscillators, and Growth of Doped Quartz Crystals ( Book )
1 edition published in 1970 in English and held by 1 library worldwide
Quartz crystals were grown by the hydrothermal method in NaOH solutions. Rates of growth in the AT and Z directions were measured for undoped and doped quartz (Mg(2+), Ga(3+), V(5+)), using various temperature gradients. All dopants, except Mg(2+), gave rates of growth lower than undoped quartz. Oscillators made of various synthetic and natural Brazilian crystals were irradiated with 5 MeV electrons and effects of irradiation on frequency and on Q-values were measured over the temperature range 77-550 degrees K. Frequency changes and reductions in Q appeared at various temperature ranges. For a High-Q SARP crystal (5 MHz in 5th harmonic) the frequency change by irradiation with about 1,000,000 rads reached about 700 Hz, and appeared mainly below 200 degrees K, just where the strongest thermoluminescence appeared. With the same crystal Q-values at a few temperature ranges were found to be sensitive to irradiation, and in these ranges the crystal even ceased oscillating after irradiation. Most effects of irradiation were canceled by heating to about 500 degrees K. Other crystals exhibited similar radiation effects. (Author)
Anomalous isomer shift ratios in eu151 and eu153 ( Book )
1 edition published in 1965 in English and held by 1 library worldwide
Anomalous isomer shift rations in Eu151 and Eu153 are discussed. Results are given of recoilless absorption measurements carried out with Eu2O3, EuSO4 and Eu metal absorbers at 20K using the 21.7 keV transition of Eu151 and the 97 KeV and 103 keV transitions of Eu153
Generation, transport and photoemission processes in molecular crystals ( Book )
1 edition published in 1967 in English and held by 1 library worldwide
Transient photocurrent measurements are employed to study carrier generation and transport processes in iodine and sulphur. The spectral quantum yield for photogeneration of holes in iodine exhibits two peaks: one at 0.45 microns and amounting to 7 percent, the other at about 0.3 microns and amounting to 17 percent. A detailed study of the effect of doping and crystal-growth conditions on transport in sulphur reveals that the hole drift mobility can be controlled over wide limits whereas the electron drift mobility is insensitive to variations in growth conditions and doping. Photoemission of holes and electrons from a metal contact into anthracene has been observed and studied. Useful criteria for distinguishing between such photoemission and spurious effects originating from bulk and surface photoconductivity have been obtained. In the case of holes, the measurement provides a direct means of determining the spectral distribution of the absolute quantum yield of the photoemission process. (Author)
Electron density ionization rate and approach to thermal equilibrium behind shock waves by means of microwave techniques ( Book )
1 edition published in 1964 in English and held by 1 library worldwide
The following subjects are investigated: Improvement in .e microwave diagnostics of shock waves; Investigations in the details of the time dependence and the shape of the microwave attenuation in shocks of air at pressures of 1 and 5mm of Hg; Measurements of the peak microwave attenuation of shock waves in argon and neon; The effect of constrictions and taper sections on the shock speed and on the microwave attenuation; Experiments with an electrical discharge shock tube; Cons.uction of a 4mm Fabry-Perot interferometer; Testing a 4mm carcinotron
X-ray excitation of the second positive and first bands of nitrogen ( Book )
1 edition published in 1964 in English and held by 1 library worldwide
It is shown that x-rays can produce emission of light in air and can excite the second positive and first negative bands of nitrogen found so prominently in aurorae
Crystal chemistry and growth of low magnetic anisotropy crystals ( Book )
1 edition published in 1968 in English and held by 1 library worldwide
A method to grow mixed cation substituted yttrium iron garnets (YIG) where the cations are calcium and silicon is described. Special flux solvent is used, based on lead oxide and is free of fluorine. Crystals of the composition (Y(3)-x-y)Ca(x)Bi(y)) (Fe2) (Fe(3-x)) O12 with x varying from 0.4 to 1.2 and y from 0.01 to 0.5 are produced. Some of the crystals could be prepared to contain Mo(6+) up to Z = 0.05. The crystals have a much lower saturation magnetization than YIG depending on the value of x. The microwave resonance absorption has a linewidth in the order of about 30 oersteds. The Curie temperature of the crystals are relatively high and even for x = 1.2 it is above 200C. Single crystals with a composition Yb3 Fe(5-x) Ga(x)O12 with x varying from 0.5 to 4.0 were grown from a PbO-PbF2 flux and the growth conditions were compared. Polycrystalline Cd Cr2S4 material was prepared by two different methods doped with Fe57. Polycrystalline Mo(6+), Ca(2+) and Si(4+) substituted YIG compounds have been prepared and the crystallographic unit cell reported. (Author)
Investigation on color centers and luminescence in insulating crystals ( Book )
1 edition published in 1968 in English and held by 1 library worldwide
Thermally stimulated luminescence (TSL) and conductivity (TSC) in KBr, x-excited at LAT were measured simultaneously. Most TSL peaks were correlated to TSC peaks. Re-excitation with F-light resulted in high intensity TSC peaks at 143 and 218K and low TSL at 146 and 223K. V light gave different results. Optical bleaching of the F- or F'-bands increased some and reduced other glow peaks. Hexagonal (6H-alpha SiC) silicon carbide crystals including iron and nitrogen were examined. The absorption showed weak bands at 0.62 and about 0.9 microns. The decay of the blue luminescence nearly fitted a power law with slopes of less than one for decay times up to 2msec. Short wavelength components of the band decayed faster compared with those at longer wavelengths. The TSL showed one glow peak near 115K with an activation energy of 0.12-0.13 ev. The TSL and TSC of a Brazilian natural quartz crystal and a synthetic Ge-doped sample as well as their re-excitation and bleaching effects are also described. (Author)
Spectroscopy in the vacuum ultraviolet ranging from 40 to 500 a ( Book )
1 edition published in 1970 in English and held by 1 library worldwide
The spectra of Be(III), Be(IV), Fe(VII) to Fe(XI), Co(IX), to Co(XI), Ni(X), to Ni(XI), Cu(X), to Cu(XIII), Zn(XI) to Zn(XIII), Ga(XII), Ge(XIII), Y(IX) to Y(XIII), Zr(X) to Zr(XIV), Nb(XI) to Nb(XV), and Mo(XII) to Mo(XVI) were studied. These spectra were produced by an intense vacuum spark, operated in a triggered mode. Radiative transitions from autoionizing levels of Be III were observed close to the Lyman alpha line of Be IV. These transitions were classified and the dependence of their intensities on the discharge parameters was determined. A new method for estimating electron temperature was suggested. A new phenomenon of line splitting in extremely dense plasma was observed. The study of the fifth row elements is difficult due to the lack of previous investigation. Here some pioneer work was done. More than 200 new lines of Y, Nb, Zr, and Mo were identified, and a great part of them classified. A new X-ray spectrometer was invented and built to facilitate the study of X-ray spectra emitted from the spark. (Author)
X-RAY EXCITATION OF FLUORESCENCE ( Book )
1 edition published in 1965 in English and held by 1 library worldwide
An X-rayed crystal of Al203 was heated to a fairly high temperature where it emitted a very strong R line radiation of very large intensity. This may result from radiation centers that have been caused by the X-ray radiation transferring their energy to the levels of the R line or a reconversion from a different valence state such as Cr2+ into Cr3+. A special lead-shielded box was designed for placing over the X-ray tube and the spectrometer in order to provide protection from the X-rays scattered over a large angle
 
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