Information theory link between MaxEnt and a key thermodynamic relation

We focus attention on the particular thermodynamic relation . Using information theory concepts we show that, for a reversible process in which intensive variables change, microscopic considerations related to this thermodynamic relation make the informational contents of, respectively, and MaxEnt equivalent. The pertinent demonstration is obtained when trying to ascertain the corresponding equilibrium microscopic probability distribution.     

On the spreading and localization of risky information in social networks

We propose a model for the localization of risky information in social (scale free) networks where we assume that risky information can propagate only between “mutually trusted nodes” (MTN). We propose an algorithm to construct the MTN network and show that there is a critical value of trusted nodes below which information localizes. This critical value increases drastically if a fraction p of nodes does not transfer information at all. We study the fraction of initial messengers needed to inform a desired fraction of the network as a function of the average number of trusted nodes and discuss possible applications of the model also to marketing and to the spreading of a disease with very short incubation time.     

Investigation of nonlinear optical properties of organic dye by Z-scan technique using He-Ne laser

The third-order nonlinear optical properties of Basic Green 1 dye were measured by the Z-scan technique and measurements were carried out at different concentrations and several incident intensities. The results showed that the Basic Green 1 dye exhibited large nonlinear refractive coefficient () and nonlinear absorption coefficient () at the wavelength 632.8 nm of He-Ne. The negative sign of the nonlinear refractive index n₂ indicates that this material exhibits self-defocusing optical nonlinearity. These results show that Basic Green 1 dye has potential applications in nonlinear optics.     

The luminescence of Sm in alkaline earth borophosphates

The temperature-dependent luminescence of Sm²⁺ ions in MBPO₅ was studied. At low temperature, Sm²⁺ in this series shows 4f⁶→4f⁶ luminescence with only a single emission line observed for the transition, revealing that only one crystallographic cationic site is available for Sm²⁺ in all the hosts. With increasing temperature, the emission intensity of the transition increases whereas that of the transitions decreases. The transitions of Sm²⁺ were observed in BaBPO₅ and its intensity increases with increasing temperature. At , a broad band of the 4f⁵5d→4f⁶ luminescent transition of Sm²⁺ in SrBPO₅ and BaBPO₅ with maximum at appears due to the thermal population. The lifetime of the transition was recorded at different temperatures, showing a single exponential decay for Sm²⁺ in SrBPO₅ and BaBPO₅ but a non-single-exponential decay in CaBPO₅.     

Fluorescence and solvatochromism of a merocyanine dye with a high quadratic polarizability in solutions and polymer films

The influence of medium polarity on the spectroscopic and photophysical properties of 2-[(2E,4E)-6-(1,3,3-trimethyl-2,3-dihydro-1H-2-indolyliden)-2,4-hexadienyliden]malononitrile (THDM) in solutions and polymer matrices is studied at room temperature and 77 K under conditions of steady-state and pulsed laser excitation. A large bathochromic shift of the absorption spectra observed upon an increase in the solvent polarity is caused by a strong increase of the dipole moment in the ground state () on going to an excited Franck-Condon state (). Based on the solvatochromic data, the quadratic polarizability was calculated to be , which is close to the experimentally determined value . A strong narrowing of the fluorescence spectra in comparison with the absorption spectra at room temperature is observed upon an increase in the solvent polarity caused by a decrease in the bond length alternation parameter and by weakening of vibronic interactions in the singlet excited state. The mirror symmetry of the absorption and fluorescence spectra of THDM in ethanol at 77 K is explained by the increase of the electrostatic interactions between the solvent and merocyanine molecules. The dynamic fluorosolvatochromism of THDM in the picosecond range is caused by molecules reorientations of the polar environment occurring during a time period consistent with the dielectric relaxation time of these molecules.     

Photoisomerization dynamics study on cis-azobenzene derivative using ultraviolet-to-visible tunable femtosecond pulses

We performed the transient absorption measurement and the first rate equation (RE) analysis for cis isomer of 4-carboxy-2′,6′-dimethylazobenzene to clarify the quantitative difference between the photoisomerization process and the thermal relaxation process from the excited state. The RE analysis enabled us to determine the cis-to-trans photoisomerization rate per each pump pulse to be 3% under the condition of the 430 nm, 150 fs pump pulse with energy of 200 nJ. Moreover, the signal due to the yielded trans molecules appearing in the transient absorption was assigned from the following observed result: the transient absorbance change at the 380 nm probe mostly decreased within 300 fs after the 430 nm pulse pumping and then slowly decreased to zero, while the absorbance change at the 350 nm probe had a positive constant component in the over one picosecond time region. The RE analysis showed that this constant component is due to the yielded trans molecules, and its positive value is due to the fact that the absorption cross-section of the -to- transition in their trans molecules is larger than that of the -to- transition in the original cis molecules.     

Theoretical study of local lattice structure of Mn in perovskite fluorides A2MF4 (A=K, Rb; M=Mg, Zn, Cd) series

A theoretical method for investigating the inter-relation between the molecular structure and electronic structure has been established on the basis of the 252×252 complete energy matrices for a 3d⁵ configuration ion in a tetragonal ligand field. By means of this method, which is independent of the X-ray diffraction, the local structure of the paramagnetic Mn²⁺ ion in perovskite fluorides A₂MF₄ (A=K, Rb; M=Zn, Mg, Cd) are determined directly by analyzing the EPR spectrum of octahedral Mn²⁺ center in A₂MF₄ crystals and the optical absorption spectrum of the (MnF₆)⁴⁻ cluster. It is shown that, comparing with the octahedral cubic structure, the local micro-structure in the vicinity of Mn²⁺ displays an elongated distortion when and a compressed distortion when , and ΔR vs. as well as ΔR vs. in the distortion region is, respectively, approximately linear. Simultaneously, the theoretical zero-field-splitting parameters , and are in good agreement with the experimental values.     

Quantum mechanics of Klein-Gordon-type fields and quantum cosmology

With a view to address some of the basic problems of quantum cosmology, we formulate the quantum mechanics of the solutions of a Klein-Gordon-type field equation: (∂_t²+D)ψ(t)=0, where and D is a positive-definite operator acting in a Hilbert space . In particular, we determine all the positive-definite inner products on the space of the solutions of such an equation and establish their physical equivalence. This specifies the Hilbert space structure of uniquely. We use a simple realization of the latter to construct the observables of the theory explicitly. The field equation does not fix the choice of a Hamiltonian operator unless it is supplemented by an underlying classical system and a quantization scheme supported by a correspondence principle. In general, there are infinitely many choices for the Hamiltonian each leading to a different notion of time-evolution in . Among these is a particular choice that generates t-translations in and identifies t with time whenever D is t-independent. For a t-dependent D, we show that regardless of the choice of the inner product the t-translations do not correspond to unitary evolutions in , and t cannot be identified with time. We apply these ideas to develop a formulation of quantum cosmology based on the Wheeler-DeWitt equation for a Friedman-Robertson-Walker model coupled to a real scalar field with an arbitrary positive confining potential. In particular, we offer a complete solution of the Hilbert space problem, construct the observables, use a position-like observable to introduce the wave functions of the universe (which differ from the Wheeler-DeWitt fields), reformulate the corresponding quantum theory in terms of the latter, reduce the problem of the identification of time to the determination of a Hamiltonian operator acting in , show that the factor-ordering problem is irrelevant for the kinematics of the quantum theory, and propose a formulation of the dynamics. Our method is based on the central postulates of nonrelativistic quantum mechanics, especially the quest for a genuine probabilistic interpretation and a unitary Schrödinger time-evolution. It generalizes to arbitrary minisuperspace (spatially homogeneous) models and provides a way of unifying the two main approaches to the canonical quantum cosmology based on these models, namely quantization before and after imposing the Hamiltonian constraint.     

Real-time monitoring of InAs QD growth procedure on InP substrate by spectral reflectance

Using an in situ spectral reflectance (SR) method, we monitored the growth procedure of InAs QD layer on InP substrate grown by low-pressure metalorganic chemical vapor deposition. The surface reconstruction of the InP buffer layer at 530 °C under P-rich condition was determined by the subtraction SR and explained to be (2 × 4)-like structures composed of the P-dimers and [1 1 0] In-dimers. The [1 1 0] and SR signals at different wavelengths showed different behaviors, which was interpreted to be caused by As/P exchange reaction and the other diverse surface processes. This analysis was confirmed by the comparison between SR signal and multibeam optical stress sensor data.     

L to M shell transitions and model comparisons for radiative opacities of sodium fluoride plasma

The radiative opacities of hot dense sodium fluoride (NaF) plasma have been studied in the case of local thermodynamic equilibrium (LTE). The spectrally resolved opacity in the case of and is taken as an example to illustrate the absorption structures of the NaF plasma. The transitions from L to M shells of sodium and fluoride are the main contributions for the plasma absorptions. The isodense opacities of NaF plasma are studied at a density of and temperatures of 20-60 eV. Detailed comparisons among the results of the detailed term accounting (DTA), detailed configuraion accounting (DCA), unresolved transition array (UTA) and average atom (AA) model codes, which have been developed independently in China in the past few years, are performed for both the spectral resolved and mean opacities. Good agreements are found at a temperature of 40 eV and a density of , but discrepancies appear at a temperature of 50 eV and a density of .     

Exact results for systems of electrons in the fractional quantum Hall regime II

In a previous work [O. Ciftja, Physica B 404 (2009) 227] we reported the exact calculation of energies for the fractional quantum Hall Laughlin state at filling factor for systems with up to N=4 electrons in a disk geometry. The purpose of this brief extension of the earlier work is to report similar exact results for the other Laughlin state at filling factor . We use the same method of orthogonal Jacobi variables adopted in the earlier work.     

Photoluminescence studies in sol-gel derived Zno films

The photoluminescence (PL) properties of high quality ZnO thin films grown on Si (1 0 0) substrates using spin coating technique are investigated as a function of temperature in the range 10-300 K. The PL spectra shows dominant donor bound excitonic emission along with free exciton related emission in the UV region. The corresponding activation energy of thermal quenching is found to be . The parameters that describe the temperature dependent red shift of the band-edge transition energy are evaluated using different models. The broadening of the PL peak due to increase in temperature is mainly attributed to the exciton-LO phonon coupling.     

Measurements of insulator band parameters using combination of single-electron and two-electron spectroscopy

We describe the application of low energy time-of-flight coincidence (e,2e) spectroscopy for measurements of the energy band parameters of a dielectric. The (e,2e) spectrometer can operate also in a single-electron mode by switching off coincidence conditions, and can be used for recording electron energy loss spectra (EELS). Thus, the combination of (e,2e) and EELS allows the measurement of energy gap E_g, valence bandwidth ΔE_val, electron affinity χ and excitonic levels position E_ex of a dielectric. The energy band parameters of LiF film deposited on Si(001) surface are measured: ΔE_val=      

Electrolytic coloration and spectral properties of OH-doped KBr polycrystals

OH⁻-doped KBr polycrystals were colored electrolytically by using a pointed cathode and a flat anode. Characteristic O⁻, OH⁻, U, Cu⁺ and absorption peaks were observed in resolved absorption spectrum of uncolored polycrystals. Herein the position of the absorption peak at room temperature was determined by using a Mollwo-Ivey plot. Characteristic V₂, V₃, Cu⁺, , I₂ and F spectral bands were observed in Kubelka-Munk functions of colored polycrystals. Current-time curve for electrolytic coloration of an OH⁻-doped KBr polycrystal and its relationship with electrolytic coloration process were given. Formation and conversion of color centers were explained.