Luminescence of AgCl excited by u.v. laser light

The spectral distribution and decay of the blue-green luminescence of AgCl has been measured at very low temperatures, using u.v. laser excitation. A structure was observed in the emission band at 77°K. The decay consists of three processes: a) a very fast process which follows the laser pulse (10^–8 sec), b) a fast exponential process which is also observed with low intensity u.v. excitation,(10^–4–10^–5 sec) and, finally, c) a slow exponential process (seconds).     

Hydrogen-like recombination X-ray lasers using ps pulse drivers

We propose a scheme for producing high gain recombination X-ray lasers on hydrogen-like Balmer transitions by irradiating fibre targets with a 2 ps Chirped Pulse Amplification CPA beam of a Nd-glass laser facility. Very high gain coefficients for H-like C, N, O, F, Na Balmer transitions are predicted. The optimum electron density and temperature for maximum gain operation scale approximately asN _e 4 × 10¹³ Z ⁷ cm^–3 and T_e 7 × 10^–3 Z ⁴ eV, respectively, at the time when maximum lasing gain appears. Significant improvement in gain performance of recombination X-ray lasers is predicted by using CPA ps pulse drivers.     

Temperature dependence of the effective work function for the BaO - W system

The temperature dependence of the work function has been examined for the BaO-W system for degrees of coating less than 1 and about 1 in the range 700–1400 °K; it is found that a monomolecular film gives a negative sign of this coefficient in this temperature range ( /T 10^–4 –10^–3 eV/deg). At 1000–1200 °K, the temperature coefficient is almost zero, while at 1200–1400 °K there is a positive value. If the covering is less than monomolecular, the sign is positive throughout the entire temperature range (/T 10^–4 eV/deg).Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 65–70, September, 1971.We are indebted to N. I. Éngovatova for direct assistance with the measurements, and to V. Rumyantsev for advice.     

Development of a very low energy μ+ beam at PSI

At PSI we are investigating the technique of decelerating an existing very intense secondary beam of surface ⁺ (4 MeV) to an energy of 10 eV using appropriate moderators. These ⁺ can then be used as a source of a tertiary beam of low energy muons with tunable kinetic energy between 10 eV and 10 keV.With a 1000 A layer of solid Argon deposited on an Al substrate we obtain a moderation efficiency (with respect to the number of incoming surface ⁺) of the order of 10^–4.Results of our investigations and the present status of the project are presented together with future plans and possibilities.     

Damage created by high-current-density implants of phosphorus into 〈100〉 and 〈111〉 silicon wafers

The damage left by high-current-density, 9 A/cm², implants of 120 keV phosphorus into 100 and 111 silicon oriented substrates was investigated as a function of the fluence in the range 4×10¹⁵–1.5×10¹⁶/cm². The samples were analyzed by 2 MeV He⁺ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at 450 °C at a fluence of 4.5×10¹⁵/cm². As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 100 substrates than for 111 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.     

Discretization of the thermal excitation in highly excited matter

In this paper the thermal energy diffusion for quantum particles is described. The quantum heat transport equation is obtained. It is shown that, for a short-time thermal excitation (of the order of the relaxation time), the excited matter response is quantized on the different levels (atomic, nuclear, quark) with quantum thermal energy equalE ^atomic 9 eV,E ^nuclear 7 MeV, andE ^quark 139 MeV.     

Theory of electron escape from the surface of liquid helium

We have studied the properties of an electron bubble close to the surface of liquid³ He, by using a Density Functional approach. We find that up to an electron-surface distanced ₀ 23 Åthe bubble is stable, while at smaller distances it becomes unstable and bursts. A potential energy barrier /K _B 38°K for the thermal emission of electrons is obtained from our results, in agreement with experiments. Even when the electron-surface distance is larger thand ₀, however, tunneling through the surface layer dominates the electron escape probability. Large deviations of the electron potential energy from its ideal value are found close to the surface. These deviations have a profound effect on the calculated decay rates of the tunneling curent, which are much smaller than those obtained previously and in semi-quantitative agreement with experiments.     

Are Axidilaton Stars Massive Compact Halo Objects?

Boson stars built from a very light Kalb–Ramond axion, the dilaton or other moduli fields of effective string models could provide a considerable fraction of the non-baryonic part of dark matter. Gravitational microlensing of 0.5 M MACHOs within the halo of galaxies may indirectly "weighing" the mass of the constituent scalar particle, resulting in 10^–10 eV/c².     

Optical characterization of laser-induced crystallized silicon films

Optical absorption coefficient spectra of thin silicon films were precisely investigated using a simple reflectance system with total reflectance mirrors placed on the rear side of samples in order to cancel an interference effect in a range between 1.1 eV and 3 eV. The absorption coefficient decreased according to crystallization as the laser energy increased and it got similar to that of single crystalline silicon in the range of 1.7 eV 3 eV. However, the absorption coefficient was higher than 10² cm^–1 in the photon energy lower than 1.3 eV. This probably results from band tail states caused by defect states localized at grain boundaries in the crystallized films. 2.5%-phosphorus doped laser crystallized silicon films had a high optical absorption coefficient ( > 10⁴ cm^–1) in the low photon energy range (1.1 eV 1.7 eV) caused by free carriers produced from the dopant atoms activated in the silicon films. The experimental results gave the carrier density of 1.3 × 10²¹ cm³ and the carrier mobility of 20 cm²/Vs.     

Neutralizing a high-aperture metal-ion beam

It is found that secondary electrons ejected by the ions from the collector are responsible for neutralizing 300 sec pulses of wide-aperture ion beams (about 100–300 cm²) formed by various metals and having current densities ji of about 10^–2 A/cm² and energy _i 100 keV. A negative potential _ee=–500 V applied to the extracting electrode relative to the grounded collector improves substantially not only the beam neutralization in the transport section but also the ion generation efficiency in the accelerating gap.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 53–56, April, 1990.     

Influence of linear elastic stresses on dynamic magnetostriction of cold-rolled transformer steel

The anisotropy of dynamic magnetostriction is investigated without external stresses, in extension, and in compression. Results are obtained expressing the (B) dependence for constant elastic stresses and also — () for certain induction values. Oscillograph traces are taken of the (H) and B(H) hysteresis loops with the specimens under investigation in extension and compression.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 110–115, May, 1977.     

Influence of localized states in a semiconducting film of critical thickness on the electrical properties of thinfilm ms' is structures

The current-voltage and high-frequency capacitance-voltage (C-V) characteristics have been used to investigate the electrical properties of thin Ga₂Ses films in Me-Ga₂Se₃-Si structures (n and p type). The features of the high-frequency C-V dependences of the structures based on p-type Si are explained in the framework of a model of the MS' IS structure with donor type centers in the semiconducting S'film (the thickness of the S' film is comparable with the generalized screening length). It is shown that in the investigated structures the charge transport mechanism is due to ionization of volume centers (the activation energy of a deep donor center is 0.72 eV) in the Ga₂Se₃ film, the mechanism being enhanced by an electric field. Analysis of the high-frequency C-V characteristics showed that the majority carriers in the Ga₂Se₃ films are electrons with concentration 10¹² cm^–3; the concentration of the deep donor centers is 5·10¹⁶ cm^–3.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 83–88, January, 1981.     

Intensity of x-ray solar radiation and the value of the anomalous absorption of radio waves during periods of sudden ionospheric disturbances

An experimental statistical dependence is obtained between the intensity of the x-ray radiation of the sun in the range 1–8 å (I_1–8) and the value of the anomalous absorption of radio waves at a frequency of I=13 MHz during periods of sudden ionospheric disturbances. This dependence has the form ₁₃ I _1–8 ^0.8 cos , and can be used for the operative classification of bursts of x-ray radiation. Its character is explained by a decrease in the coefficient of the losses of electrons with a rise in the intensity of the x-ray radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1558–1562, November, 1978.I wish to thank E. A. Benediktov and V. V. Belikovich for their interest in the work and their critical evaluation of its results.     

Compatibility of higher rho-resonances with the pion form factor data

A realistic pion form factor model respecting the usual fundamental principles supplemented by reasonable assumptions is constructed by means of conformai mapping having some specific uniformization properties. The model includes the contributions of higher rho-resonances without any conflict with analyticity, provides a certain flexibility for the asymptotic behaviour and depends just on the physical parameters. The best fit of all existing data is achieved with(770),'(1600) and the asymptoticst ^–3/2. The predicted values of the pion charge radius, P-wave isovector scattering length, as well as theI=J = 1 scattering amplitude at the experimental measurable region coincide with the world averaged data.Dedicated to the 30th anniversary of the Joint Institute of Nuclear Research.The authors are indebted to Prof. V. A. Meshcheryakov, Dr. S. B. Gerasimov and Dr. D. Krupa for many stimulating and illuminating discussions.     

Attenuation of powerful ruby laser pulses in the atmosphere by resonant absorption of water vapor

The attenuation of a ruby laser pulse at the wavelength = 6943.8å is calculated under conditions of spectroscopic saturation for a parallel beam and a diverging beam with divergence angle = 10^–5 rad. It is shown that deviation from the Bouguer law may reach 45% at a path length = 2 km for an initial power level of I₀ = 0.5I_s for the parallel beam, and 20% for I₀ = 0.25I_s for the divergent beam (I_s, saturation power).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–12, February, 1978.     

The behavior of copper impurity in CdSnAs2

Single crystals of n-type CdSnAs₂ with a carrier concentration of 2 ·10¹⁷–4 ·10¹⁸ cm^–3 and mobility (3 to 6) · 10³ cm²/V ·sec were copper doped by diffusion saturation at temperatures from 400 to 570C. As a result of the study of the electrical properties of the doped crystals it was established that the copper in CdSnAs₂ is a fast-diffusing acceptor impurity. The solubility of Cu depends primarily on the donor-center concentration and has clearly a retrograde character. Low-temperature heat treatment (over the 200–400C range) of the Cu-doped specimens results in an increase in the acceptor concentration. The form of the log R(10³/T) curve indicates the existence of acceptor centers with an ionization energy of 0.05 eV in the Cu-doped CdSnAs₂ specimens.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 7, pp. 39–44, July, 1973.     

Electro-Strong Interaction and High Q 2 Events at HERA

A previously proposed unified field theory of electro-strong interactions requires two scales of length within hadrons, 10^–15 and 10^–18 m respectively, and the onset of new phenomena at the shorter scale. Studies at the HERA electron–proton collider at the shorter scale have revealed a possible excess of high-transverse momentum events, as expected, with Q ² 30,000 (GeV/c²). The collider is currently being upgraded. This will permit a clearer test to be carried out.     

Self interstitial trapping at Hf impurities in Niobium

After electron irradiation at 15 K of Niobium doped with¹⁸¹Hf the trapping of defects at the Hf impurities was observed by means of the perturbed angular correlation method. The results are interpreted as the formation of Hf-Nb mixed dumbbells which are formed at 5 K and are stable up to 80 K.     

Ferromagnetic resonance and magnetic crystallographic anisotropy of monocrystalline lithium ferrite films

The crystallographic anisotropy constant K₁ of monociystalline lithium ferrite films was measured by the methods of ferromagnetic resonance and rotational moments. The presence of uniaxial anisotropy in the plane of a film with the constant K_u 10₃ erg · cm^–3 is established experimentally. The nature of the uniaxial anisotropy is explained by the anisotropy of the stresses in the plane of the film, a formula is obtained to compute the angle of deflection of the easy magnetization axis from the crystallographic direction. An estimate is made of the difference in the stresses along the axes (_x–_z) 10¹⁰ dyne · cm^–2.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 86–89, September, 1973.