A sensitive non-destructive method for measuring the Nd doping concentration in Nd : YAG with high spatial resolution

This paper reports on an experimental method for measuring in Nd:YAG the Nd doping concentration (C) with high sensitivity (0.01 at.%Nd) and high spatial resolution (50 m). The method is based on the measurement of the fluorescence lifetime _f of the upper Nd laser level. Additional parameters required to determine C are the intrinsic fluorescence lifetime ₀ and the quenching parameter Q. The measured values of _f, ₀ (256.47±0.14 s) and Q (4.45±0.40×10²⁰ cm^-3) allow us to calculate the Nd concentration C with an absolute accuracy of 0.1 at.%Nd. By using this method C is measured at the outer surfaces of standard laser rods and at the faces of boule slices (with diameters of up to 50 mm). The obtained results demonstrate a detection sensitivity of 0.01 at.%Nd. PACS 42.70.Hj; 81.70.Fy     

Double quantum transitions in free radicals

The observation of double quantum transitions on three kinds of free radicals (DPPH, DPANO, ultramarine) at temperatures of liquid nitrogen is described. Signals having an absorption and emission character were observed in the 12-5 MHz–18 MHz frequency band in the direction parallel to the external magnetic fieldH ₀ and their dependence on different parameters was studied.Bloch equations were solved for two mutually perpendicular high-frequency fields and expressions were found for the components of dynamic susceptibility in theH ₀ direction. The experiments agree with theory.The possibility of using double quantum transitions for measuring relaxation times is discussed.

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(DPPH, DPANO, ) . 12,5MHz–18MHz H ₀, ; . H ₀. . .

     

The single crystal diffraction patterns of silicon

A triple-crystal diffractometer is used to study the single crystal diffraction patterns of Si (111), (220), (333) and good agreement with the dynamical theory of X-ray diffraction on perfect single crystals is found. This proves the possibility of using Si single crystals as in X-ray spectroscopy for a double-crystal spectrometer with a high resolving power as well as for studying very narrow diffraction patterns by means of a triple-crystal diffractometer.

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Si

Si (111), (220), (333); . Si , .

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The authors thank R. ida and F. Hájek for designing and making the automatic equipment for measuring the curves and V. Smutná and A. Irra for carefully performing the auxiliary work.     

Frequency-mixing scheme for the production of tunable narrowband XUV radiation (91–95 nm): application to precision spectroscopy and predissociation in diatomic molecules

Tunable narrowband extreme ultraviolet radiation in the range 91–95 nm is produced by sum-frequency mixing of the outputs of a visible pulsed dye amplifier (seeded by a ring dye laser) and of a seeded second-harmonic Nd:YAG laser and subsequent frequency tripling in a gas jet of xenon. The capability of this scheme to provide tunable narrowband extreme ultraviolet radiation is demonstrated in several spectroscopic studies. The bandwidth of this system (0.01 cm^-1) is deduced from a recording of absorption spectra of the 4p⁵(²P_1/2)6d, J=1 line in krypton. The applicability of the system for gas-phase molecular spectroscopic studies is demonstrated in recordings of the Werner bands (4,0) in H₂ and (5,0) in D₂ at unprecedented absolute accuracy. Line-broadening studies are performed on the b¹_u⁺,v=5 valence state in N₂, yielding a lifetime of 210±25 ps. A singlet–triplet perturbation, giving rise to an accidental predissociation in an excited ¹ Rydberg state in carbon monoxide at an excitation energy of 107680 cm^-1, is analyzed in high resolution. PACS 42.65.Ky; 32.80.Rm; 33.20.Ni; 33.80.Gj; 42.60.By     

Singularities of Jost functions and potentials

The possibility of determining a potential from given singularities of Jost functions is investigated. It is proved that forN poles the problem can be reduced to the solving of a system ofN linear nonhomogeneous equations and in the case of discontinuities along a cut to the solving of a nonhomogeneous integral equation. The obtained potentials are a superposition of exponential potentials.

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. , N N . .

     

Parametric amplification and harmonic generation in the VUV and XUV

To overcome limitations in the high harmonic conversion efficiency, the possibility of parametric amplification in the VUV and XUV is considered. Potential approaches, including parametric gain transfer from low- to high-order processes, are discussed. Experimentally, a near two photon resonant parametric gain scheme in xenon, excited by femtosecond KrF laser radiation at _p=248 nm, was investigated, leading to signal (_s) and idler (_i) emissions at 149 nm and 760 nm according to 2_p=_s+_i. For the signal field at 149 nm an exponential increase with density and length is obtained. By tuning the excimer laser radiation slightly towards the two-photon resonance, a macroscopic amplification of about 50 at 149 nm was measured. In addition, a sum-mixing signal at 106 nm according to _sum=2_p+_i, showing a similar exponential increase as the 149-nm signal, is observed, which indicates a coupling of both processes with a gain transfer by the common idler field. PACS 42.65.Ky     

Double hypernuclei and the Λ-Λ interaction

The binding energy of the double hypernucleus Be¹⁰ analyzed using an -particle model. A relationship is found between B, the binding energy of two -particlcs, and ¯V, the - potential integral. For the experimental value B = 17.5 Me V ¯V varies from 250 to 850 MeV-F³ according to the form of the - potential used.In conclusion, I wish to thank S. N. Kryuchkova for carrying out these calculations on a Minsk-2 electronic computer. I also wish to thank my senior colleague, V. A. Filimonov, for his support in the completion of the present work.     

The inelastic reactions πp→λ(⌆) K with allowance for the contribution of branch cuts

The method of complex angular moments is used to analyze the experimental data on the inelastic reactions p ()K, taking into account branch cuts in the j-plane in the eikonal approximation. An optical model for the backward scattering is considered. Agreement with experiment is obtained in the region of small angles for the reactions (⁰)K⁰. In the case of ^–P K⁰(^–K⁺) processes, agreement is obtained with the experimental results for large (180) scattering angles.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 26–30, August, 1972.     

Measurement of two-photon absorption cross-section in organic molecular salt with linear and circular polarized radiation

We report on the investigation of two-photon absorption (TPA) in 4-Diethylamino-N-Methyl-4-Stilbazolium Tosylate (DEST) with 40 picosecond, 1064 nm linear and circular polarization laser radiation. The TPA cross-section ₂ measured is larger for linear polarized radiation (948 GM) than that for the circular polarized radiation (840 GM). The large TPA cross-section of DEST facilitates highly directional and efficient TPA induced upconverted emission in the range of 590–640 nm even though the fluorescence efficiency of DEST is very low (0.5%). The net single pass efficiency of upconversion is 7%. PACS 42.65.-k; 42.70.Jk     

The efficient inject of high microwave powers into the overdense magnetoactive plasma in the waveguide

On the boundary vacuum — a dense magnetoactive plasma, an incident RHCP (right hand circularly polarized) wave is strongly reflected if ₀ ² / ² 1 and _ce/ > 1;, ₀, _ce are the ncident wave frequency, the plasma frequency and the electron cyclotron frequency, respectively. This reflection strongly lowers the efficiency of the plasma heating by microwaves. Our experimental study shows that a suitable matching system consisting of dielectric plates, placed in front of the plasma, can ensure practically complete transfer of the RHCP wave energy into a dense plasma. The experiment was carried out in the S band waveguide (=12·7 cm) with the power of the order of l kW.The authors wish to thank to the director of the Institute of Plasma Physics Dr. J.Váa for his interest in this work.     

Four-wave mixing in CO via the C 1Σ+ (υ′=0) state

Coherent vacuum ultraviolet (VUV) radiation was generated by four-wave difference frequency mixing (_VUV=2₁–₂) of pulsed dye laser radiation in carbon monoxide (CO). The frequency ₁ was tuned to the C ¹⁺(=0)X ¹⁺(=0) two-photon transition, while the dye laser frequency ₂ was scaned around 17650 cm^–1 which corresponds to the A ¹(=7)«C ¹⁺(=0) transition energy. The VUV intensity was found to be strongly wavelength dependent. The analysis of the spectrum revealed (i) that the VUV intensity was enhanced by the rotational levels of the A ¹(=7) state and (ii) that the off-resonance excitation in the C ¹⁺(=0)X ¹⁺(=0) two-photon transition greatly contributed to the present four-wave mixing process. The effects of pumping laser detuning, saturation and foreign gases are briefly discussed.     

The conversion electron spectra of Lu169 and Lu170

The isotopes Lu¹⁶⁹ and Lu¹⁷⁰, obtained in the fraction of radioactive Lu isotopes by bombarding a Ta target with fast protons, were measured on a double focusing -ray spectrometer. The gamma transitions are given together with the relative intensities of the conversion lines. The multipolarity of the transition is determined for some gamma transitions from the internal conversion coefficient ratios of theK andL shells.

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Lu¹⁶⁹ Lu¹⁷⁰

Lu¹⁶⁹ Lu¹⁷⁰, . - . - K L .

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We should like to thank V. Kopiva and M. Buriánek for help during the measurements.     

Double phase-matched cascaded fifth harmonic generation in single nonlinear medium by focussed laser beam

Generation of a fifth harmonic by the cascading of two phase-matched third-order processes in a single centrosymmetric nonlinear medium with a focused fundamental beam is investigated theoretically. With the help of analytical and numerical investigations the optimized conditions for maximum conversion into the fifth harmonic are found. In general the optimal position of focusing depends on the values of the mismatches k₁ and k₂ for both steps of the third order cascading (++=3; 3++=5). It is shown that for best efficiency this method of fifth harmonic generation requires specially chosen k_1,opt and k_2,opt and focusing in the center of the nonlinear media. If the phase matching parameters are fixed and they deviate from the optimal values, then the optimal strength of focusing and position of the focus spot should be calculated according to the analysis presented here. PACS 42.65.-k; 42.65.Ky; 42.79.Nv     

ЗАВИСИМОСТЬ ПОЧЕРНЕ НИЯ ФОТОГРАФИЧЕСКОЙ ЭМУЛЬСИИ ОТ ЭНЕРГИИβ-ИЗЛУЧЕНИЯ

, - - . , - , , :³²P,³⁵S ⁹⁰Sr+⁹⁰Y.     

On the zigzagging causility model of EPR correlations and on the interpretation of quantum mechanics

Being formalized inside the S-matrix scheme, the zigzagging causility model of EPR correlations has full Lorentz and CPT invariance. EPR correlations, proper or reversed, and Wheeler's smoky dragon metaphor are respectively pictured in spacetime or in the momentum-energy space, as V-shaped, A-shaped, or C-shaped ABC zigzags, with a summation at B over virtual states |B B|. An exact correspondence exists between the Born-Jordan-Dirac wavelike algebra of transition amplitudes and the 1774 Laplace algebra of conditional probabilities, where the intermediate summations |B) (B| were over real hidden states. While the latter used conditional (or transition) probabilities (A|C) = (C|A), the former uses transition (or conditional) amplitudes A|C = C|A*. The formal parrallelism breaks down at the level of interpretation because (A|C) = |A|C|². CPT invariance implies the Fock and Watanabe principle that, in quantum mechanics, retarded (advanced) waves are used for prediction (retrodiction), an expression of which is | U | = | U = U|, with | denoting a preparation, | a measurement, and U the evolution operator. The transformation | = |U or | = |U^–1 exchanges the preparation representation and the measurement representation of a system and is ancillary in the formalization of the quantum chance game by the wavelike algebra of conditional amplitude. In 1935 EPR overlooked that a conditional amplitude A|C = A|BB|C between the two distant measurements is at stake, and that only measurements actually performed do make sense. The reversibility A|C = C|A* implies that causality is CPT-invariant, or arrowless, at the microlevel. Arrowed causality is a macroscopic emergence, corollary to wave retardation and probability increase. Factlike irreversibility states repression, not suppression, of blind statistical retrodiction—that is, of final cause.Dedicated to Professor David Bohm, proponent of the EPRB version of nonseparability.     

A new approach to the problem of the anomalous magnetic moment of the electron

A heuristic model for deriving the anomalous magnetic moment of the electron is presented. A term /2 – 0.327(/)² is deduced, in better agreement with experiment than is the QED derivation of /2 – 0.328(/)². The result is strengthened by the recent non-QED account of the Lamb shift by Yu and Sachs.     

Debye screening for two-dimensional Coulomb systems at high temperatures

The grand canonical ensemble of a two-dimensional Coulomb system with±1 charges is proved to have screening phenomena in its high-temperature region. The Coulomb potential in a finite region is assumed to be (–)^–1, where is the Laplacian with zero boundary conditions on. The hard-core condition is not assumed. The model is set up by separating (–)^–1 into a shortrange part and a long-range part depending on a parameter. The self-energies are subtracted only for the short-range part and therefore a choice of is a choice of subtraction of self-energies. The method of proof is in general the same as that of Brydges-Federbush Debye screening, except that here a modification for the short-range part of the potentials is needed.     

Generation of backscattered 2 ω and 3 ω/2 harmonics of femtosecond radiation from targets with different atomic numbers

Backscattered 2 and 3/2 harmonics were investigated during the interaction of femtosecond radiation (=795 nm, t=150 fs, 10-Hz pulse repetition rate) with various targets. The harmonics were generated without changing the position of the targets from shot to shot. Various characteristics of the harmonics were analyzed and their dependences on pump radiation parameters are discussed. Efficient 2 and 3/2 harmonics were achieved for low-Z targets, whereas only second-harmonic generation was observed for high-Z materials. PACS  42.65.Ky; 52.35.Mw; 52.38.-r     

On the Surface Pressure for the Edwards-Anderson Model

For the Edwards-Anderson model we introduce an integral representation for the surface pressure (per unit surface) in terms of a quenched moment of the bond-overlap on the surface. We consider free , periodic and antiperiodic ^* boundary conditions (by symmetry ⁽⁾=^(*)), and prove the bounds We show moreover that at high temperatures ⁽⁾ is close to ^2/4 and ⁽⁾ is close to ^2/4 uniformly in the volume .