Mean field methods for atomic and nuclear reactions: The link between time–dependent and time–independent approaches

Abstact: Three variants of mean field methods for atomic and nuclear reactions are compared with respect to both conception and applicability: The time–dependent Hartree–Fock method solves the equation of motion for a Hermitian density operator as initial value problem, with the colliding fragments in a continuum state of relative motion. With no specification of the final state, the method is restricted to inclusive reactions. The time–dependent mean field method, as developed by Kerman, Levit and Negele as well as by Reinhardt, calculates the density for specific transitions and thus applies to exclusive reactions. It uses the Hubbard–Stratonovich transformation to express the full time-development operator with two–body interactions as functional integral over one–body densities. In stationary phase approximation and with Slater determinants as initial and final states, it defines non–Hermitian, time–dependent mean field equations to be solved self–consistently as boundary value problem in time. The time–independent mean field method of Giraud and Nagarajan is based on a Schwinger–type variational principle for the resolvent. It leads to a set of inhomogeneous, non-Hermitian equations of Hartree–Fock type to be solved for given total energy. All information about initial and final channels is contained in the inhomogeneities, hence the method is designed for exclusive reactions. A direct link is established between the time–dependent and time–independent versions. Their relation is non–trivial due to the non–linear nature of mean field methods. Received: 7 January 1998 / Revised version: 20 April 1998     

Optical properties of silver selenium indate films obtained by the method of pulse laser vaporization

The spectra of transmission and reflection are measured in the region of 0.4–2.5 μm on thin silver selenium indate films obtained by means of pulse laser vaporization. The magnitudes of the refractive index and absorption coefficient are calculated. The energies of interband transitions and the values of crystalline and spin-orbit splitting are determined. The experimental results for the AgInSe₂ films agree with the data for bulk crystals. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 512–514, July–August, 2000.     

Submicrometre particle size distribution from 0.1–0.45 μm in the urban plume of the city of Valladolid

Summary Particle size distribution in the urban plume of the city of Valladolid was measured with a laser spectrometer during a one-month sampling campaign carried out over the winter period. Experimental results of the number of particles covering the 0.10–0.12, 0.12–0.15, 0.15–0.20, 0.20–0.25, 0.25–0.35 and 0.35–0.45 μm ranges are presented. Using spectral analysis as a statistical technique, two 12 h and 24 h significant peaks are obtained for each size range. In order to interpret the meaning of both peaks, the hourly particle size, traffic and nitrogen oxide patterns are compared. The contribution of domestic heating, traffic exhaust emissions and the strong influence of the gas-to-particle conversion processes mainly within the 0.10–0.15 μm range, may be inferred.     

Porous-silicon coatings for photovoltaic devices

Summary Porous silicon was formed on multicrystalline Si substrates by stain etching in aqueous HF/HNO₃ solutions. In this work optical and electrical properties of the resulting films are discussed as a function of process parameters. Porous-Si films have been shown to be able to reduce surface reflectance to 3% in 350–700 nm wavelength range and their application in anti-reflection coating of photovoltaic solar cells has been demonstrated, obtaining (10×10) cm² multicrystalline Si solar cells with efficiency approaching 12% under standard AM 1.5 simulated sunlight. Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettitore di Luce), Torino, 12–13 October 1995.     

Correlated wave functions to approach the bound excited states of Li- and Be-

Explicitly correlated wave functions including a Jastrow factor to take into account the dynamical correlation effects, and a multi determinant model wave function to account for the non–dynamical correlations are used to study some metastable excited states of the negative ions Li^- and Be^-. A detailed analysis of one– and two–body properties has been carried out for these states. In particular the single–particle density as well as both the two–body inter electronic and center of mass densities have been obtained. All the calculations have been performed by using the variational Monte Carlo method.     

Study of optical properties and molecular structure of plasma polymerized diethylene glycol dimethyl ether

This paper deals with plasma polymerization processes of diethylene glycol dimethyl ether. Plasmas were produced at 150 mtorr in the range of 10 W to 40 W of RF power. Films were grown on silicon and quartz substrates. Molecular structure of plasma polymerized films and their optical properties were analyzed by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy. The IR spectra show C–H stretching at 3000–2900 cm^-1, C=O stretching at 1730–1650 cm^-1, C–H bending at 1440–1380 cm^-1, C–O and C–O–C stretching at 1200–1000 cm^-1. The concentrations of C–H, C–O and C–O–C were investigated for different values of RF power. It can be seen that the C–H concentration increases from 0.55 to 1.0 au (arbitrary unit) with the increase of RF power from 10 to 40 W. The concentration of C–O and C–O–C decreases from 1.0 to 0.5 au in the same range of RF power. The refraction index increased from 1.47 to 1.61 with the increase of RF power. The optical gap calculated from absorption coefficient decreased from 5.15 to 3.35 eV with the increase of power. Due to its optical and hydrophilic characteristics these films can be applied, for instance, as glass lens coatings for ophthalmic applications.     

Isotope shifts and accurate wavelengths in Ne II and Ne III

Transition isotope shifts of 3s–3p transitions in Ne II and Ne III are measured in Fourier transform spectra from a hollow-cathode source. Accurate absolute line-center positions of the ²⁰Ne isotope are derived for the purpose of tertiary wavelength standards in the region 2000–5000 ?. A robust statistical treatment is applied, yielding line-position uncertainties that are lower than for the Ar II secondary standards used as references. The influence of Stark shifts on both the new Ne II standards and the Ar II standards is also investigated. In addition, improved wavenumbers of the 3p–3d and 3p–4s transitions are presented, of which 12 in Ne II have been measured for the first time. Electronic supplementary material Supplementary Online Material     

Energy transfer in chemical dimers of porphyrins and chlorins by the methods of selective laser spectroscopy at 1.8–10 K

The methods of selective laser spectroscopy applied at 1.8–10 K to a glass-forming tetrahydrofuran-toluene (3∶1) mixture have revealed that in the dimers of tetrapyrrole compounds (ethane-bis-octaethylporphyrins, ethane-bis-Zn-octaethylchlorins, heterodimers of Zn-cyclopentane porphyrins) the exciton interactions (V₁₂≈118 cm⁻¹) and S-S-transfer of energy (of probability F≈11 sec⁻¹) are implemented under conditions of substantial inhomogeneous broadening (δF_1/2≈50 cm⁻¹). Upon excitation of a donor component in the dimers, one observes a strong quenching of its emission, the disappearance of the fine structure in the fluorescence spectra, a decrease in the efficiency of spectral hole burning by, approximately, an order of magnitude, and a 12-fold increase in their halfwidth. To whom correspondence should be addressed. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 500–504, July–August, 1999.     

Infrared filters and analyzers of the composition of substances based on them

Results of investigations on designing band dispersion and dispersion-interference filters for the 4–30 μm IR range and cutoff filters for the 50–300 μm region are presented. Analyzers of the composition of a substance that are designed on the basis of band IR filters and analysis procedures are described. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 734–744, September–October, 1998.     

Electronic structure of C60 films

A complete set of fundamental optical functions of fullerite (C₆₀) films in energy ranges of 2.5–5.0 and 4.0–9.0 eV is calculated using the known spectra of the imaginary and real parts of the dielectric constant. An integrated spectrum of the dielectric constant is decomposed into elementary components. Three basic parameters of each component (the maximum and halfwidth energies and oscillator strength) are determined. Based on the known theoretical calculations of fullerite zones, a scheme of the nature of these components of the dielectric constant is suggested. Udmurt State University, 71, Krasnogeroiskaya Str., Izhevsk, 426034, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 227–232, March–April, 1999.     

Influence of laser heating on the optical properties of a superhigh-modulus organoplastic material

The degree and azimuth of polarization and the indicatrix of the intensity of radiation (λ=0.63 μm) reflected by the surface of a monodirectional superhigh-modulus organoplastic material after structural transformations induced in it by CO₂-laser radiation are measured. It is shown that the space-polarization characteristics of the radiation reflected by the organoplastic material charred as a result of laser heating correspond to the parameters of radiation scattered by a nontransparent material with an isotropic surface in the approximation of geometrical optics. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 635–639, September–October, 1999.     

The Nambu–Jona–Lasinio model of light nuclei

The Nambu–Jona–Lasinio model of the deuteron suggested by Nambu and Jona–Lasinio (Phys. Rev. 124 (1961) 246) is formulated from the first principles of QCD. The deuteron appears as a neutron–proton collective excitation, i.e. a Cooper np–pair, induced by a phenomenological local four–nucleon interaction in the nuclear phase of QCD. The model describes the deuteron coupled to itself, nucleons and other particles through one–nucleon loop exchanges providing a minimal transfer of nucleon flavours from initial to final nuclear states and accounting for contributions of nucleon–loop anomalies which are completely determined by one–nucleon loop diagrams. The dominance of contributions of nucleon–loop anomalies to effective Lagrangians of low–energy nuclear interactions is justified in the large N _C expansion, where N _C is the number of quark colours. Received: 10 March 2000     

Theoretical interpretation of the vibrational spectra of methyl-substitutedS-triazine

The problems of normal vibrations of mono-, di-, and trimethyl-substituted S-triazine are solved. Assignments of the frequencies of fundamental vibrations for an aromatic ring and methyl groups are suggested. Corrections for methyl substitution for the force constants of S-triazine are determined. The groups of characteristic and noncharacteristic vibrations of the aromatic ring of S-triazine on substitution of hydrogen are established. Saratov State University, 83, Astrakhanskaya St., Saratov, 410601, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 322–325, May–June, 1998.     

Angular distribution and polarization characteristics of radiation reflected by a fibrous superhigh-modulus composite material

The effect of a smooth surface binder film and the orientation of filler fibers of unidirectional superhigh-modulus organoplastic on space-polarization characteristics of He−Ne laser reflected radiation is investigated. B. I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220078, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 926–931, November–December, 1998.     

Unrestricted symmetry-projected Hartree-Fock-Bogoliubov calculations for SD-shell nuclei

Abstact: The solution of the Hartree–Fock–Bogoliubov problem with restoration of the broken symmetries before the variation has been generalized for the use of totally unrestricted quasi–particle determinants. With this method doubly–even, doubly–odd and odd nuclei can be treated on the same footing. Comparison with the results of complete shell–model diagonalizations shows that already one–determinant representations yield a very good approximation to the exact solutions even in the middle of the 1s0d shell. The problem is especially suited for numerical implementation on parallel computers. First tests show a linear dependence of the inverse CPU time with the number of processors used. Received: 26 February 1998 / Revised version: 8 May 1998     

Investigation of the optical properties of AgGaTe2 films obtained by laser deposition

We obtain thin films of AgGaTe₂ by laser vaporization of starting crystals. The compositions of the starting crystals and of the films obtained are determined by x-ray spectral analysis, with their structure and the parameters of the crystal lattice being determined by the x-ray method. The energies of interband transitions and crystalline (Δ _cr ) and spin-orbit (Δ _so ) splitting are calculated from transmission spectra in the region of the main absorption band. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 793–796, November–December, 1997.     

Influence of iron-subgroup metals on the atomization of silicon in a graphite furnace

The regime of atomization of Si in the presence of Fe-subgroup metals was investigated with the use of a “Saturn” spectrophotometer and a “Graphit-2” electrothermic atomizer. The optimal operating parameters of the atomizer have been determined. It was established that the optimal value of the ashing and the atomization temperatures are, respectively, 900–1000°C and 2400°C, the optimal rate of temperature rise at the stage of atomization is 1400 K/sec, and the appropriate amount of Fe, Co and Ni additions is 1–2 μg. It was established that the formation of gaseous silicides of the Fe-subgroup metals, the dissociation energies of which are lower than the dissociation energies of Si oxides and carbides, increases the sensitivity for determination of Si. To whom correspondences should be addressed. Institute of Single Crystals, National Academy of Sciences of Ukraine, 60, Lenin Ave., Khar'kov, 310001, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 153–157, March–April, 1999.     

Luminescent properties of AIIB2IIIC4VI compounds

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 3, pp. 145–151, May–June, 1995.     

Spectral-polarization properties and quantum-chemical calculation of a porphyrin-chlorine heterodimer with a covalent ester bond

The porphyrin-chlorine heterodimer P-O-Chl, in which porphyrin and chlorine fragments are single esterbonded in a covalent manner, is investigated experimentally and theoretically. From absorption and polarized-fluorescence spectra of two stable P-O-Chl isomers it follows that the porphyrin and chlorine fragments preserve their individuality, and their weak interaction does not change the basic photophysical parameters of the chlorine fragment in a temperature interval of 77–293 K. Based on calculations by the method of molecular mechanics with standard parameterization of the force field and the CNDO/S method and comparison of their results with the data on polarized fluorescence, the structure of one of the two isomers is substantiated. From CNDO/S calculations, the authors estimated the energy of the states with charge transfer in the P-O-Chl system, whose lower levels are above the levels of local excited Q-states of the interacting porphyrin and chlorine fragments. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 766–775, November–December, 1997.     

Association of mono- and dimethyl ethers of chlorine 6 in ethanol-water solutions

The association of γ-mono- and 6,γ-dimethyl ethers of chlorin e₆ (I and II) in mixtures of a phosphate buffer and ethanol is studied. The number of molecules in associates and the dimerization constants are determined. The formation of the dimers of compound I and dimers and associates of a higher order for II is established. It is found that, unlike I, the shift of the Q absorption band of the dimer toward larger wavelengths is rather great as compared to the monomer band for II; it exceeds 30 nm, which is uncommon for porphyrins. This difference of spectral changes in association of I and II is attributed to the dissimilar character of interaction of their molecules with each other and with the molecules of the surroundings, and also to the structural features of the dimers. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 440–444, July–August, 2000.