IR Reflection of Thin Bi4Ge3O12 Films

The spectra of IR reflection of the systems thin Bi₄Ge₃O₁₂ film–substrate made of molten -SiO₂ quartz in the region 10–1600 cm^–1 at 295 K are investigatedterpretation of fundamental vibrations in the region 10–800 cm^–1 and two phonon processes in the region 800–1600 cm^–1 are considered.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.     

Photoconductivity of highly excited A IV B VI thin films

We report the results of picosecond photoconductivity measurements in photosensitive electrolytically deposited PbS and vacuum evaporated PbTe polycrystalline films. We determine Auger recombination to be the prevailing carrier recombination mechanism in highly excited PbTe and PbS films and found Auger coefficients _A5×10^–28 cm⁶ s^–1 for PbTe and _A5.3×10^–29 cm⁶ s^–1 for PbS for carrier concentration changes N>10¹⁸ cm^–3. The results indicate that the low mobility values are controlled by intergrain carrier scattering. We have studied the thermal annealing influence on picosecond photoconductivity of the films.     

Temperature dependence of anisotropy in monocrystalline lithium ferrite films

A study of crystallographic and uniaxial anisotropy in monocrystalline Li-ferrite films in the temperature range 4.2–550°K is presented. The experimental results K₁(T) agree well with calculations based on the one ion model with crystalline field coefficients of a_A=–2.77 ·10^–2 cm^–1, a_B=3.34 · 10^–2 cm^–1. An experimental function K_u(T) is obtained which does not contradict the assumption that anisotropic stresses are responsible for the development of uniaxial anisotropy in Li-ferrite films.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 113–116, August, 1973.     

Infrared properties of quartz fibres

The IR properties of micron-size amorphous SiO₂ fibres have been investigated between 400 cm^–1 and 1400 cm^–. For the single scattering size and shape effects have been measured and compared with theory. The observed diffuse reflection of quartz wool can be explained qualitatively by the Kubelka-Munk theory for multiple scattering.reported at the 5th International Conference on Infrared and Millimeter Waves, October 6–10, 1980     

Extra-drude contribution to the far infrared conductivity oxygen deficient YBCO films

We measured reflectance spectra R(v) of oxygen deficient Y₁Ba₂Cu₃O_7–x (YBCO) films of different thickness, with critical temperatures between 85 and 87 K. Measurements were made at room temperature between 15 and 25000 cm^–1. The measured R(v) have a maximum below 100 cm^–1 and then decrease for v 0. This low frequency behaviour of R(v) can be accounted for by considering a relevant extra-Drude contribution to the far infrared optical conductivity of YBCO.     

Investigations on the excited states of Eu2+ in CaF2-and SrF2-crystals by two-photon absorption spectroscopy

The two-photon-excitation spectra of Eu²⁺:CaF₂ and Eu²⁺:SrF₂ have been studied at 4.2 K in the region between 24,100cm^–1 and 28,100cm^–1. Besides a broad two-photon absorption region two groups of sharp lines at 27,600cm^–1 and 28,000cm^–1 in Eu²⁺:CaF₂ (27,670cm^–1 and 28,080cm^–1 in Eu²⁺:SrF₂) are identified with the transitions 4f ⁷:⁸ S _7/24f ⁷:⁶ P _7/2,⁶ P _5/2. It is shown that the 4f-states of Eu²⁺ in this host lattice differ significantly in their physical properties from the same states of the isoelectronic Gd³⁺. For these transitions, however, the calculated two-photon absorption rates are in good agreement with the experiments.A project of the Sonderforschungsbereich 65 Festkörperspektroskopie, Darmstadt-Frankfurt, supported by the Deutsche Forschungsgemeinschaft     

Laser-induced free-carrier absorption in Si single crystal

The transmitted energy density in thin single Si crystal, wafers is measured at=1.06 m as a function of the incident energy density for a Nd laser pulse of 30 ns duration. Non-linear effects begin to become important at about 0.3 J/cm². The contribution due to free-carriers is separated from the interband one by using measurements made at low energy density and at different sample temperatures in the 20°–150 °C range. The time dependence of the free-carrier concentration and of the lattice temperature is computed for different values of the Auger constant. The experimental data in the 0.2–2.5 J/cm² energy density range are fitted with an Auger constant of 10^–30 cm⁶s^–1.Work supported in part by M.P.I. and G.N.S.M.-C.N.R.     

Electronic absorption in silicate mineral of copper

The electronic absorption spectrum of chrysocolla, a silicate mineral of copper, has been studied at room and liquid air temperatures. The observed bands were satisfactorily explained as belonging to Cu²⁺ ion subjected to tetragonal and spin-orbit fields. A good fit between the theoretical and observed band positions was obtained for the following crystal field parameters:Dq=–1400 cm^–1 Ds=–3000 cm^–1 Dt=–800 cm^–1 =–800 cm^–1     

Space- and time-resolved investigation of gain lines in Na-like copper

We report space- and time-resolved measurements of the gain coefficient for four gain lines in sodium-like copper. The lines investigated include the twon = 1 transitions 5g–4f and 5f–4d at 11.1 nm and 10.3nm and the twon = 2 transitions 6g–4f and 6f–4d at 7.2 nm, and 6.9 nm. The investigations were carried out for four irradiation intensities from 4 × 10¹² W/cm² to 3 × 10¹³ W/cm² using the Asterix IV high-power iodine laser at Garching (wavelength 1.315 µm, pulse duration 450 ps).The main results may be summarized as follows: On varying the laser intensity it was found that the highest values of the gain could be seen at an irradiation of 8 × 10¹² W/cm². For then = 1 lines the spatial maximum of the gain occurred at a distance of 300 µm from the target, and for then = 2 lines at 200 µm. The temporal gain maximum occurred at a time of 1.8 ns after the pulse maximum. The gain values range up to 2.6 cm^–1.Dedicated to the memory of the late Prof. Shi-shen Chen, who contributed to the early phase of this work     

Evolution of the homogeneous IR spectrum of a highly vibrationally excited molecule as a result of a change in its vibrational energy

Using a photodissociation technique, we have measured the IR spectrum of thev ₂₁ mode of the (CF₃)₃ CI molecule with a vibrational energy ofE ₂=42500±3500 cm^–1 which is more than two times the dissociation energy. The experimental spectrum of a Lorenzian shape with a halfwidth of ₂=10.8±1.5 cm^-1 has been analyzed simultaneously with the results of the preceding work (₁=8.6±0.6 cm^-1) that were obtained at a lower vibrational energy (E ₁=36500±2500 cm^–1).     

Relation between the fine structure of the vibrational spectrum of the crystal lattice and the cation distribution in Co1+2xFe2−3xSbxO4 ferrites

The infrared reflection spectra in the region of lattice vibrations (1500–200 cm^–1) of ferrite spinels Co_1+2xFe_2–3xSb_xO₄ with x=0.0–0.4 are investigated. The permittivity spectra are calculated using the Kramers-Kronig relations. A dispersion analysis of the ₁(v); ₂(v) spectra, carried out using the multiscintillator model, enabled the fine structure of the bands of the spectra to be determined. It was found that for CoFe₂O₄ ferrite the short-wave band (v=590 cm^–1) consists of two components, while the long-wave band (v=375 cm^–1) consists of fur components. Since cobalt ferrite is inverted spinel, in which there are only Fe³⁺ ions in the tetra positions, the doublet structure with v=590 cm^–1 must obviously belong to vibrations of the ion groups FeO₆ and CoO₆, while the second band may belong to vibrations of the ion complexes consisting of the tetra-cation (Fe³⁺), oxygen and the three closest octa-cations [3Fe], [2Fe1Co], [2Co1Fe] and [3Co]. The replacement of some of the iron ions with antimony leads to the appearance of additional lines from the short-wave edge of both bands. The intensity of these lines increases as the value of the diamagnetic substitution increases, which enables the highest-frequency component to be uniquely related to the vibrations of the complex formed by the tetra-cations Fe³⁺ or Co²⁺, the anion and the three octa-cations Sb⁵⁺.V. I. Ul'yanov-Lenin Kazan State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 105–109, July, 1995.     

Estimation of the Optimum Concentration Interval of the Contents of Praseodymium, Neodymium, Europium, Holmium, and Erbium in a Solution

Based on the electronic absorption spectra of Pr³⁺, Nd³⁺, Eu³⁺, Ho³⁺, and Er³⁺ ions in 1 M aqueous solutions of chloric acid, calibration graphs have been constructed in a concentration of metals–optical density of a solution format for different frequencies. The band for praseodymium was used at 22,520 cm^–1, for neodymium at 17,380, 13,480, and 12,560 cm^–1, for europium at 25,380 cm^–1, for holmium at 18,580 and 15,580 cm^–1, and for erbium at 39,160, 26,480, and 19,160 cm^–1. The errors in determining the concentration of the indicated elements as a function of their content have been calculated. It is shown that for perchloric solutions of praseodymium it is possible to correctly determine its contents within the concentration range 0.1–1.5% at a frequency of 22,520 cm^–1; for neodymium the ranges are 0.4–1.0, 0.3–1.0, and 0.5–1.0% at 17,380, 13,480, and 12,560 cm^–1, respectively; for europium 0.4–1.5% at 25,380 cm^–1; for holmium — 0.2–1.5 and 0.4–1.5% at 15,580 and 18,580 cm^–1, and for erbium the range is 0.4–1.0% at frequencies of 39,160, 26,480, and 19,160 cm^–1.     

Effect of electron irradiation on the electrophysical properties and photoluminescence of nuclear-transmutation-doped gallium arsenide

The Hall effect, the electric conductivity, and the photoluminescence spectra of electron irradiated (E=1 MeV, D=1.1·10¹⁵–3.8·10¹⁸ cm^–2) nuclear-transmutation-doped n-GaAs crystals and crystals of n-GaAs doped by the standard metallurgical method were investigated. The energy spectrum of the radiation-induced defects, determined from the Hall effect and DLTS spectra [E1–E5 traps with ionization energy 0.08, 0.14, 0.31, 0.71, and 0.9 eV, respectively (from the bottom of the C band)], is the same in nuclear-transmutation-doped and standard GaAs and satisfactorily describes the experimental dependence n(D). The rate of introduction of traps E1, E2 decreases as n₀ increases (from 1.3 cm^–1 in GaAs with n₀ — 10¹⁷ cm^–3 to 0.7 cm^–1 in GaAs with n₀ 10¹⁸ cm^–3). The rate of removal of charge carriers () increases as n₀ increases, irrespective of the method of growth and doping of GaAs. The isovalent impurity In in nuclear-transmutation-doped gallium arsenide with N_In 10¹⁸ cm^–3 decreases .Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 45–51, April, 1991.     

Instability of the molecular structure of monobenzoporphin to the alternation of the macrocycle bond lengths and its manifestation in the electronic spectra

Quantum-chemical calculations of the geometric structure of the molecules of monobenzoporphin (H₂ MBP) and monobenzoporphin with methyl and ethyl substituents in the five-member rings (H₂MBPm) have been carried out by the restricted and unrestricted Hartree-Fock methods with the AM1 Hamiltonian (AM1 RHF and AM1 UHF methods). The calculation of the above-indicated molecules by the AM1 RHF method without restrictions on their symmetry has given, for them, a planar structure with an alternation of the lengths of the bonds along the 18-member azacyclopolyene and the symmetry C _1h for their aromatic part. The calculation of the transitions to the excited electron Q states in such a structure by the CNDO/S method has shown that these states are characterized by large hypsochromic shifts (~3000–4000 cm^–1 ) relative to the Q levels of porphin (H₂P), which is in contradiction with the experimental data, according to which these shifts are bathochromic and comprise = –330 cm ^–1 and = –750 cm^–1. Optimization of the geometry of the H₂ MBP and H₂MBPm molecules by the AM1 UHF method gives, for them, a structure with equal lengths of the bonds along the 18-member azacyclopolyene with a symmetry differing insignificantly from the D _2h symmetry; elements of the structure with a lower symmetry and an alternation of the lengths of the bonds are retained in the condensed pyrrolenine and benzene rings. The calculation of the shifts of the Q levels in the H₂MBPm molecule of this geometry relative to the analogous levels in H₂P has shown that they are bathochromic and equal to = –520 cm^–1, and the RHF calculation with optimization of the geometry of the molecule and restrictions on the effective symmetry D _2h of the 18-member azacyclopolyene has given = –350 cm^–1 and = –430 cm^–1. The restrictions imposed on the C ₂ symmetry of the H₂MBP molecules by the RHF method are inadequate to equalize the lengths of the bonds along the 18-member azacyclopolyene. The calculations of the energy of the B levels of the monobenzoporphyrins considered also lend credence to their geometric structure with equal lengths of the bonds along the 18-member azacyclopolyene.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 712–721, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Tunable far-infrared solid-state lasers based on hot holes in germanium

The basic principles for achieving population inversion and stimulated emission in the far-infrared fromp-Ge are discussed. In the heavy-light hole lasing mode a broad gain region is found resulting in a broad multimode spectrum due to intracavity modes. By attaching external plates of germanium a single mode operation is realized. The obtained powers are in the W range with linewidths of 0.2 cm^–1. A single mode magnetically tunable coherent source is achieved with the light hole cyclotron resonance laser. With external mirrors a tuning range from 20 to 120cm^–1 with magnetic fields between 1 and 6 T is achieved. The intensity of the single mode is in the order of W, the linewidth below 0.2 cm^–1.     

Micro-Raman spectroscopy in polycrystalline CuInSe2 formation

The crystalline formation of CuInSe₂ thin films has been investigated using micro-Raman spectroscopy and AES composition analysis. It is confirmed that the Raman peaks are stongly dependent on the surface morphology and the Cu:In:Se ratio. In the films annealed at 315°C, crystalline grains larger than 2 m show Raman peaks at 174 cm^–1 and 258 cm^–1. The In content is very low and the Cu:Se ratio is about 1:1 in these grains. The low In concentration is thought to be due to the formation of In₂O₃ on the surface. On the other hand, random structures of 1–2 m grains found in films annealed at temperatures below 305°C show peaks at 174 cm^–1 and 186 cm^–1 instead of 258 cm^–1 and have a Cu:In:Se ratio of 1:1:3–4. Thus the 186 cm^–1 peak is thought to be related to a Cu, In-deficient phase when compared to stoichiometric CuInSe₂. The optimum annealing condition was found by analyzing the Raman spectra and composition of different crystalline CuInSe₂ grains. Films annealed under this condition exhibited a clear Raman peak at 174 cm^–1 and consisted of clusters of crystals less than 1 m in size.     

Optical and Paramagnetic Properties of Synthetic Diamond Single Crystals with a Low Content of Nitrogen

Optical and paramagnetic properties of synthetic diamond single crystals grown by the temperature gradient method in the Fe-Co-C and Fe-Co-Al-C systems using split-sphere high-pressure apparatus have been investigated. For crystals with a high (>5·10¹⁷ cm^–3) nitrogen concentration a good agreement of the concentrations of single substitution nitrogen atoms obtained from EPR, IR, and UV measurements was observed. For crystals with a low ((0.5–5.0)·10¹⁷ cm^–3) nitrogen concentration, there was no correlation between the results of substituting nitrogen concentrations obtained by the methods mentioned. It is shown that this behavior is attributable to the transition of the substituting nitrogen atoms from the paramagnetic neutral to nonparamagnetic positive charge state due to compensation by the boron impurity.     

Determination of the unsaturated losses and of the saturation intensity in the KrCl excimer laser

The unsaturated losses , and the saturation intensityI _s, were measured in an uv-preionized KrCl laser for optimized He and Ne based laser gas mixtures. The measurements were made as a function of the specific power loading and of the total pressure of the laser mixtures. Higher values for andI _s were found for the Ne-based laser mixture than for the He-based mixture. At 45 kV charging voltage and at 355 kPa of total pressure we measured =0.053 cm^–1 andI _s =9.4MW/cm² for the Ne based mixture, and =0.035 cm^–1 andI _s =5.1MW/cm² for the He based mixture.     

Gas formation in liquid in initial stages of a pulsed discharge

Gas formation in electrolytes with=10^–2–10^–4–1cm^–1, distilled water = 10^–5-1.5 ·10^{–6 –1}cm^–1, and chemically pure n-hexane in the initial stages of formation of discharge with rectangular voltage pulses of 0.67 and 1.85 sec duration is investigated. The experimental results are compared with the results of approximate calculations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 42–47, November, 1972.The authors thank V. V. Ryumin for taking part in the discussion of the results and V. V. Lopatin for participation in the experiments with electron-optical light amplifier.