Luminescence and lasing properties of neodymium- and uranium-activated inorganic laser liquids

An attempt was made to describe and show the possibilities of new inorganic neodynium- and uranium-activated laser liquids: SO₂-GaCl₃-NdCl₄; SO₂Cl₂-GaCl₃-NdCl₃-UO₂Cl₂; POCl₂-MCl_n-NdCl₃-UO₂Cl₂ for development and synthesis of direct nuclear reaction-excited lasers. Luminescence data presented in the work were used to calculate the luminescence parameters of the laser liquids such as oscillator strengths f, probability of spontaneous radiation A, intermultiplet luminescence branching coefficient β, cross-section for induced radiation σ, luminescence decay time τ, quantum yield η, and others. It is shown that the oscillator strengths of the normal absorption bands of Na³⁺, which play the main part in the pumping processes, exceed the oscillator strengths of Na³⁺ for aqueous and many other nonaqueous systems. In the luminescence excitation spectra of the Na³⁺ ion, bands are isolated in the range 400–1000 nm atλ _rec =1.06 μm. With excitation, luminescence occurs through the⁴F_3/2→⁴I_{9/2,11/2.13/2} channels. Luminescence spectral data are related to the lasing parameters. The threshold lasing energy is∼18 J/cm³. For a resonator with mirros h₁=100% and h₂=20, 40, 56, and 80%, the lasing energy is∼20–120 MJ/cm³ in the pumping energy range 18–180 J/cm³. The differential efficiency is ∼0.2% The substantial angular radiation divergence (θ∼4·10⁻² rad) and strong thermostatic distortions that occur in the active element (dn/dT≈−1.9·10⁻⁴K⁻¹) are a disadvantage of laser liquids. It is shown that operation of neodymium- and uranium-activated inorganic liquid lasers is stable under the present conditions. A. I. Gertsen Russian State Pedagogical University, Moika Embankment, 48, St. Petersburg, 191186, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 607–619, September–October, 1997.     

Atmospheric gamma rays in the energy region 40–1000 GeV

A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented by the power lawJ _r (E)= 129·4E ^{−2·62±0·12} photons m⁻² sr⁻¹sec⁻¹ GeV⁻¹ at an effective atmospheric depth of 14·3 g cm⁻²; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP _r (E, 0)=8·2 × 10⁻⁴ E^2.60±0.09 photons g⁻¹sr⁻¹sec⁻¹ GeV⁻¹. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray production spectrum.     

XUV generation from plasma produced by a XeCl excimer laser on a Cu target

Summary We present a detailed study of XUV and soft X-ray emission from Cu plasma produced by an excimer laser at intensitiesI _L≦8·10¹¹ W/cm². The XeCl excimer laser (ψ≈308 nm) delivers pulses with energyE _L≈2.3 J, temporal durationt _L≈100 ns and brightnessB≧10¹⁴ W/cm² sr. We recorded a spectral conversion efficiency η=0.5% eV⁻¹ forI _L=4·10¹¹W/cm² in the aluminium window at 73eV with a harder X-ray tail around ≈400eV. We also measured the dependence of X-ray signal on laser intensity and viewing angle. Experimental results have been compared with some analytical laser-plasma interaction models.     

Structural phase transitions in Pd0.8 Si0.2 and Pd0.75 Si0.20 Ag0.05 alloys observed by pac

The phase transition in the alloys Pd_0.8 Si_0.2 and Pd_0.75 Si_0.20 Ag_0.05 have been investigated through the quadrupole interaction of¹¹¹Cd impurities. The quadrupole interactions were measured by means of the TDPAC technique from room temperature up to about 870 K. The variation of the quadrupole interaction with temperature in the alloy PdSiAg shows aT ^3/2 dependence below and above 629 K, with coefficientsB=5.43(25)·10⁻⁵ K^−3/2 andB=3.70(15)·10⁻⁵ K^−3/2, respectively. This demonstrates that the alloy undergoes a phase transition around 629 K. The existence of two electric field gradients observed in the alloy PdSi,V _zz (1)=3.47(54)·10¹⁷ V/cm² andV _zz (2)=2.29(36)·10¹⁷ V/cm², indicates that there are two different¹¹¹Cd sites. The corresponding fractionsf ₁ andf ₂ strongly depend on temperature. Below 520 K, most¹¹¹Cd nuclei are subject to the higher EFGV _zz (1) (f ₁≈70%), whereas above 520 Kf ₁ falls rapidly to zero andV _zz (2) becomes dominant. The temperature dependences of thef ₁ andf ₂ reveal a picture of the phase transition between the two crystal structures.     

Beat frequency intercomparisons of127I2 stabilized ion lasers at 514.5 nm

International comparisons of I₂ stabilized ion lasers operated at 514.5 nm have shown a laser frequency reproducibility of 2·10⁻¹⁰ v to 5·10⁻¹² v. These results encouraged the international acceptance of the wavelength value λ_vac=514.673467 for thea ₃ hyperfine component of the¹²⁷I₂ line 43-0P(13).     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

Preliminary results on the operation of a 2270 kg cryogenic gravitational-wave antenna with a resonant capacitive transducer and a d.c. SQUID amplifier

Summary In November 1985 the gravitational-wave antenna of the Rome group, installed at CERN, has started operating. It consists of a 5056 aluminium cilinder 3 m long, 2270 kg heavy, cooled at 4.2 K. The antenna vibrations are detected by means of a resonant capacitive transducer that together with the bar makes a two-coupled-oscillator system. The low-noise amplification is obtained with a d.c. SQUID amplifier. The frequencies of the two resonant modes are:v _-=907.116 Hz andv ₊=923.083 Hz, with merit factorsQ ₋=3.2·10⁶ andQ ₊=5.6·10⁶. The sensitivity to short gravitational bursts, expressed in terms of effective noise temperature, is 18 mK. This corresponds to a change in the metric tensor whose Fourier transform isH=1.1·10⁻²¹ Hz⁻¹. For monochromatic waves the antenna is sensitive (SNR=1) toh∼2·10⁻²⁵ in a band width of about 1/3 Hz, with a three months integration time.

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Riassunto Nel novembre 1985 è stata messa in funzione l'antenna gravitazionale del gruppo di Roma, installata al CERN. Questa consiste di un cilindro d'alluminio 5056 lungo 3 m e pesante 2270 kg, raffeeddato a 4.2 K. Le vibrazioni dell'antenna vengono rivelate mediante un transduttore capacitivo risonante, che assieme alla sbarra forma un sistema di due oscillatori accoppiati. L'amplificazione a basso rumore è ottenuta con un amplificatore a d.c.-SQUID. Le frequenze dei due modi risonanti sono:v _-=907.116 Hz ev ₊=923.083 Hz, con fattori di meritoQ ₋=3.2·10⁶ eQ ₊ =5.6·10⁶. La sensibilità per brevi fiotti di onde gravitazionali, espressa in termini di temperatura efficace di numore, è 18 mK. Questa corrisponde a una variazione di tensore metrico con trasformata di Fourier:H=1.1·10⁻²¹ Hz. Per le onde monocromatiche l'antenna è sensibile (SNR=1) ah∼2·10⁻²⁵ in una banda di circa 1/3 Hz, con tempo d'integrazione di tre mesi.

     

EPR of Fe3+ ion and symmetry of [AIF5·H2O]2? complex ion in (NH4)2AIF5·H2O single crystals

We used the spin-Hamiltonian method for the analysis of the electron paramagnetic resonance (EPR) spectrum of Fe³⁺ as a probe ion in (NH₄)₂AlF₅·H₂O single crystalline basic material. The theoretical expressions for the magnetic field (at which the fine structure transition lines appear) versus the angle between the magnetic field and the axis of symmetry of the magnetic complex are also given. These values were calculated by applying the perturbation theory to the second-order terms. From the experimental results (at 300 K and 9.21 GHz), the spin-Hamiltonian parameters were deduced:D=(668±10)·10⁻⁴ T,E=(−56±10)·10⁻⁴ T,a=(−54±10)·10⁻⁴ T,F=(30±10)·10⁻⁴ T. An isotropic superhyperfine structure was evidenced for the five fluorine ions. The obtained EPR data were used to determine the local symmetry of the Al³⁺ ion. A good agreement with X-ray diffraction measurements was found.     

Optical properties of Tm,Mg:LiTaO3 laser crystal

A Tm, Mg co-doped LiTaO₃ crystal has been grown by Czochralski method. Room temperature polarized absorption spectra and fluorescence spectrum of the Tm, Mg:LiTaO₃ crystal were measured and analyzed. The maximum absorption cross-section is 6.0791 × 10⁻²⁰ cm² at around 790 nm with full width at half maximum of 5 nm. The emission cross-section of ³ F ₄ manifold was 2.2 × 10⁻²⁰ cm². The spectroscopic parameters of Tm³⁺ ion were calculated by applying the Judd-Ofelt approach, and the intensity parameters Ω₂, Ω₄, and Ω₆ were obtained to be 7.71 × 10⁻²⁰, 1.09 × 10⁻²⁰, and 1.16 × 10⁻²⁰ cm², respectively. The branching ratios and radiative lifetimes were also presented and the radiative lifetime of Tm^{3+ 3} F ₄ → ³ H ₆ transition is 968.3 μs. The results were also analyzed and compared with other Tm³⁺ doped hosts.     

Measurement of atomic parameters for the3 D 1 state of I–II

The decay rates of the³ D ₁ level of I–II and the 3s ₂ level of neon have been measured by the magnetic-field power dip method. The decay rate at the zero-pressure limit is found to be 7.1 MHz/2π for the³ D ₁ level. The collision cross-section for excited I ions with helium atoms equals 0.19×10⁻¹⁵ cm². This work was supported by project MR-1.5-1.05.     

The temperature and light intensity dependence of photorefraction in LiNbO3

In the paper the dependence of the photorefraction (PhR) in LiNbO₃ and LiNbO₃−Fe (0.1 wt%, 0.3wt%) crystals on light intensity (within 10¹⁶–10²³ quanta·cm⁻²·s⁻¹ at wavelengths 496.5 nm and 600 nm) and temperature (in the region 100–500 K) is studied. For all the crystals the limiting values of PhR are similar and atT=293 K Δn _sat ^lim ≈3·10⁻³. In LiNbO₃ the temperature dependence of PhR in the range 100–500 K requires to take into account at least two trapping centres.     

Intramolecular photoinduced electron transfer in Pd-porphyrin-quinone in the picosecond time range

Photoinduced electron transfer (PET) was studied in toluene solutions of the Pd-porphyrin-quinone (Pd-PQ) dyad by flash photolysis in the picosecond time range and by a luminescence method. It is found that Pd-PQ has a high rate of intercombination conversion K_isc=(7.7±0.2)·10¹⁰ sec⁻¹. Competing intramolecular PET occurs from the lower excited singlet state of the dyad with the rate constant K _et ^s =(2.7 ±0.3)·10¹⁰ sec⁻¹. Therefore, ∼74% of excited molecules from the dyad make a transition to the triplet T₁ state and 26% take part in intramolecular PET resulting in formation of radical products. The radical products relax to the ground state with the rate constant K=(7.4±0.2)·10⁹ sec⁻¹. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 11–18, January–February, 1999.     

The dynamics of accumulation of electrically active radiation defects on implantation of graded-band-gap HgCdTe films grown by MBE

The dynamics of accumulation of electrically active radiation defects under ion doping of epitaxial Cd _x Hg _1−x Te films is studied for various distributions of film composition in the implantation region. The epitaxial films were irradiated by boron ions at room temperature in the continuous regime, with the dose ranging within 10¹¹−3·10¹⁵ cm⁻², energy — 20–150 keV, and ion current density — j = 0.001–0.2 μA·cm⁻². It is found that the natural logarithm of the introduction rate of electrically active radiation defects linearly depends on the epitaxial-film composition in the range of mean projected path of implanted ions. An analysis of the experimental data shows that the dynamics of accumulation of electrically active radiation defects is determined by the epitaxial-film composition in the implantation region. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 25–28, September, 2006.     

Role of charge-transfer complexes in oxygen quenching of excited states of anthracene derivatives in the gas phase

Oxygen quenching of excited triplet and singlet states of gas-phase anthracene and its derivatives that have similar energies of the lower triplet levels but widely different oxidation potentials (0.44 < E_ox < 1.89 V) was studied. Quenching rate constants for singlet (k_S^O2) and triplet (k_T^O2) states in addition to the fraction of oxygen-quenched singlet and triplet states q_{S 1}(T₁^O2 were determined from the decay rates, fluorescence intensities, and delayed fluorescence as functions of oxygen pressure. It was found that k_S^O2 values vary from 2·10⁴ (9,10-dicyanoanthracene) to 1.2·10⁷ sec⁻¹·torr⁻¹ (anthracene, 9-methylanthracene, 2-aminoanthracene) and k_S^O2 values from 5·10² to 1·10⁵ sec⁻¹·torr⁻¹. The k_S^O2 values for anthracene, 9-methylanthracene, and 2-aminoanthracene, which have fast rates of interconversion from S₁ to T₁, are close to the rate constants for gas-kinetic collisions and are independent of the oxidation potentials (E_ox). The quenching rate constants k_S^O2 for the other anthracene derivatives and k_T^O2 for all studied compounds decrease with increasing free energy of electron transfer ΔG_ET, which indicates the important role of charge-transfer interactions in the oxygen quenching of singlet S_1- and triplet T₁ states. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 36–42, January–February, 2008.     

Influence of additional metal ions on the ratio of the rates of intermediate product transformations in the hydrolysis of adenizine-5′-triphosphoric acid catalyzed by divalent Cu ions

It was shown earlier that the hydrolysis of the (CuATP²⁻)₂ dimeric complex to CuADP⁻ and inorganic phosphate P _i was an irreversible reaction. The main intermediate hydrolysis product, the formation of which should be taken into account at comparatively early hydrolysis stages, was the IntK pentacovalent intermediate. It was formed in parallel with hydrolysis to CuADP⁻ and P _i through the common intermediate product (CuATP²⁻)₂OH⁻ — DOH⁻. We studied the influence of the addition of various concentrations of Mg²⁺ ions to the reaction mixture at pH 7.1–7.2, a range for which the kinetics of hydrolysis is sensitive to the rate constants of deactivation of DOH⁻ active centers (conjugated with CuADP⁻ formation and occurring via the formation of IntK). The conversion of ATP above which stationary hydrolysis regime was observed decreased as the concentration of Mg²⁺ grew. The DOH⁻ $ \underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}}$ \underset{{OH^ - }}{\overset{{OH^ - }}{\longleftrightarrow}} IntK equilibrium according to the conversion of ATP was established more rapidly, and it was to a greater extent shifted toward IntK. It was assumed that hydrated Mg²⁺ linked as a second metal ion with ATP β and γ phosphate groups hydrated IntK much stronger than DOH⁻. The Cu · OH₂ · AMP complex played the role of a common acid catalyst and hydrated DOH⁻ better than Mg²⁺ · OH₂. The selective hydration of DOH⁻ by the CuOH₂ · AMP complex at early hydrolysis stages directed the process toward the formation of IntK, which caused the appearance of an induction period in the formation of CuADP⁻.     

X-ray determination of thermal expansion of cadmium fluoride and lead fluoride

The lattice parameters of CdF₂ andβ-PbF₂ have been determined over the temperature range 300–670 K. The coefficient of expansion at room temperature is 21·3 × 10⁻⁶ K⁻¹ and 25·4 × 10⁻⁶ K⁻¹ for CdF₂ and PbF₂ respectively and it increases linearly with temperature over the range of temperature covered. The Grüneisen parameter decreases with temperature in both the crystals.     

Optical properties of the ternary compound Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se:Co

We present the results of experimental studies of the optical properties of cobalt-doped Cd _x H_1−x Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·10¹⁸, 5·10¹⁹, and 1·10²⁰ cm⁻³ at T = 90 K and 300 K. The composition (x = 0.18) of the Cd _x Hg_1−x Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations N_Co < 5·10¹⁸ cm⁻³. For N_Co ∼ 5·10¹⁸ cm⁻³, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007.     

Heat capacity of MnBr2·4H2O near the antiferromagnetic transition temperature

Heat capacity of MnBr₂·4H₂O has been measured in the critical region around the Neel temperature. The data can be fitted, over a restricted range of |t|⩽10⁻², to the asymptotic power law. The critical exponents and the amplitudesA andA′ are not consistent with any theoretic predictions. However when scaling constraints are imposed, their values agree with the parameters of Ising model. Corrections to scaling are necessary to extend the range of the fit to |t|>10⁻². The correction terms are asymmetric giving −1·15±0·25 as the ratio of the amplitudes of the lowest order correction terms,D andD′ above and belowT _c. This value is in agreement with the recent predictions of the renormalisation group theory.     

Unambiguous detection of monopoles

Summary The fission of a vortex line along the trajectory of a monopole in a superconducting medium is an unambiguous signature of a monopole. The numbern of the (stable) daughter vortices determines the monopole strengthg withg=2nφ/4π where ϕ₀=2.07·10⁻⁷ G cm².

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Riassunto La fissione di una linea di vortice lungo la traiettoria di un monopolo in un mezzo superconduttore è indice sicuro della segnatura di un monopolo. Il numeron di vortici figli (stabili) determina la forza del monopolog cong=nϕ₀/4π, dove ϕ₀=2.07·10⁻⁷ G cm².

     

Kinetics of formation of O2(1Σ) molecules in reactions involving excited O2(1Δ) oxygen molecules and I(2P1/2) iodine atoms

The results of our experimental study of the kinetics of formation of O₂(¹Σ) molecules in energy-exchange reactions O₂(¹Δ) + I(⁵ p,² P _1/2) and O₂(a,¹Δ) + O₂(a,¹Δ) are presented. The ratio of rate constants was obtained for these reactions (4800 ± 300). Setting the rate constant of the deactivation of O₂(¹Σ) molecules on CO₂ molecules at 4.1 · 10^–13 cm³/s, we evaluated the rate constants for these reactions at a temperature of approximately 330 K: (1.7 ± 0.2) · 10⁻¹³ and (3.6 ± 0.5) · 10⁻¹⁷ cm³/s, respectively.