CNDO/2 Calculations for Hydroxy Stretching Bands of Intramolecular Hydrogen Bonds in cis−Cyclohexane-1,3-Diol and cis−3-Aminocyclohexanol

CNDO/2 calculations are used to predict the hydroxy stretching frequency and intensity of the intramolecular hydrogen bonds in the title compounds. The predictions are compared with experimental data.     

Quantum‐Chemical Investigation of Hydrogen Bonds in Porphin

Using the DFT Becke–Lee–Yang–Parr exchangecorrelation threeparametric functional (B3LYP), we have calculated the geometry, the electron density distribution, and the vibration frequencies for pyrrole, porphin, and their 13 analogs with a regularly varying structure. It is shown that the determining role in the change in the frequencies of stretching and outofplane deformation vibrations of porphin compared to pyrrole is played by intramolecular hydrogen bonds at the porphyrin macroring center. We have separately considered and compared with the data for porphin complexes of pyrrole with different intermolecular hydrogen bonds: with an aromatic ring (NH··· cluster formed by the pyrrole selfaggregation in the liquid state) and an unshared electron pair (NH···OH₂ and NH···NC₄H₄ clusters). The degree of participation of the NH group in the hydrogen bonds increases in the series NH··· cluster, porphin, NH···OH₂ and NH···NC₄H₄ clusters.     

SF6 and H2 Broadening and Shifting in the Fundamental Vibrational–Rotational Band of Hydrogen Fluoride

Optics and Spectroscopy - SF6 and H2 broadening and shift of the vibration–rotation lines in the fundamental band of hydrogen fluoride have been investigated. Using mathematical modeling of...     

Mechanism of Intramolecular Transfer of a Proton and an Electron in an Excited State of 4′‐Amine Derivatives of 3‐Hydroxyflavone

The intramolecular transfer of a proton in 4amine derivatives of 3hydroxyflavone was investigated in binary solvents, which are a mixture of polar and nonpolar liquids. The dependence of the efficiency of the intramolecular transfer of a proton in an excited state on the frequency of the exciting light has been revealed, which is due to the spectral inhomogeneity of the molecules of fluorophors in binary solvents. A scheme of the processes of intramolecular transfer of a proton and an electron in 4amine derivatives of 3hydroxyflavone is suggested.     

Spectral‐Luminescence Characteristics of Polyphenyls and Polyacenes in the Gas Phase in Electron‐Beam Excitation

The spectra of electronenergy loss, excitation functions, and fluorescence spectra in excitation of the vapor of polyphenyls and polyacenes by electron beams of different energies are determined. The influence of successive complication of the molecules under study on these spectralluminescence characteristics is tracked. Unlike the optical absorption spectra, in the spectra of electronenergy loss of all the substances studied one observes a band which is related to the singlettriplet transition S ₀–T ₁. The transitions up to S ₀–S ₅ are recorded in excitation of the molecules by highenergy electrons, including the region of vacuum ultraviolet. From the functions of fluorescence excitation the authors have determined the excitation thresholds that correlate with the energies of the S ₁ levels, except for pyrene in which the S ₀–S ₁ transition is forbidden and does not show up not only in photon excitation but also in electronbeam excitation, although the intercombination forbiddenness in the latter case is removed and the S ₀–T ₁ band is observed.     

Spectral‐Luminescence and Generation Properties of 1‐Aza‐2‐Methyl‐6‐Aminopyrene and of Its Protolytic Forms

Spectral manifestations of protolytic forms of 1aza2methyl6aminopyrene in ethanol and aqueous solutions are investigated. The ionization constants of the protolytic forms are determined. The generation properties and photostability of a neutral molecule and a cation in excitation by an excimer XeCl laser are studied.     

Mechanism and Dynamics of the Photoinduced Fe–O2 Bond Breaking in Oxyhemoglobin

Russian Physics Journal - The paper is devoted to time-resolved studies of human hemoglobin, including excited electronic states and relaxation processes, quantum yield and dissociation electronic...     

Theoretical and Experimental Study of the Conformation and Vibrational Frequencies of N‐Acetyl‐L‐alanine and N‐Acetyl‐L‐alaninate

The vibrational frequencies of N‐acetyl‐L‐alanine (NAAL), its potassium salt (NAALK) and its free anionic form (NAAL^?) are calculated using density functional theory (B3LYP) combined with the 6‐311 + + G(d,p) basis set. The experimental Raman spectrum of solid NAALK and the scaling factors for calculated values are discussed as well. The three species are characterized by intramolecular NH…O hydrogen bonds leading to the formation of a five‐membered ring. As indicated by the intramolecular (N)H…O distances and by the ν(NH) frequencies, the strength of the intramolecular hydrogen bond is ordered as follows: NAAL^? < NAALK < NAAL^?. Owing to their difference in the coupling with other vibrational modes, the in‐plane and out‐of‐plane vibrations do not reflect the strength of the hydrogen bond.     

Determination of the Spin–Spin Coupling Constant in Hydrogen Deuteride HD and Estimates of the Manifestation of Axion-Like Particles

An experimental value of the spin–spin coupling constant in deuterated molecular hydrogen HD has been obtained, J _pd = (43.112 ± 0.005) Hz (300 K), while investigating two gaseous samples at pressures of 95 and 155 atm. The experimental result does not coincide with Jpd = (43.31 ± 0.05) Hz that was calculated theoretically by Helkager et al. The observed discrepancy ΔJ _pd ≈ (0.20 ± 0.05 Hz) may point to a manifestation of the involvement of light pseudo-scalar (axion-like) bosons with a mass m _a ≈ 1 keV/c² in the spin–spin coupling of the HD proton and deuteron.     

Steady‐State and Time‐Resolved Emission Studies of 6‐Methoxy Quinoline

Abstract

Steady‐state absorption, fluorescence excitation, and emission spectra of 6‐methoxy quinoline (6‐MQ) were measured at room temperature in cyclohexane, dioxane, ethanol, acetonitrile, water, and water–dioxane solvents. Absorption spectra of cyclohexane, n‐hexane, and isopentane solutions show resolved vibronic structure at room temperature. However, the excitation spectrum of cyclohexane solution is structureless and is found to be emission wavelength dependent, indicating the formation of at least two distinct species in the ground state. Similar behavior was observed in dioxane and water–dioxane solutions. For all other solutions, the fluorescence excitation spectrum of 6‐MQ was found to be the same for different emissions. Emission of 6‐MQ in all solvents consisted of two bands with their maxima around 355 nm (I) and 430 nm (II), the actual positions and the relative intensities being dependent on the solvent used. The bands I and II were respectively attributed to normal and protonated/H‐bonded species of either ¹L_a or ¹L_b states or mixed (¹L_a/¹L_b) state of ππ* character. Fluorescence decay of this dye in all solvents monitored over each emission maximum showed biexponential behavior, and the analysis yielded two different lifetime components for each emission band. The short and long fluorescence decay components were respectively in the range of 0.30–3.00 ns and 18–20 ns. The observed emission characteristics coupled with the nature of the fluorescence polarization spectra and two different decay components for each emission suggest the existence of two different conformers having two different excited electronic states.     

What Are the Roles of Hydrogen in Infinite-Layer Nickelates?

<正>Even after more than 30 years of intensive effort,the understanding of physical origin accounting for the high-temperature superconductivity in cuprates remains the open question in condensed matter physics. A possible way to solve this long-standing question is to find other cuprate-analogous structures.     

Relationship of the Acid-Induced 13C Chemical-Shift Change in the α-Carbon Atom to the Stretching Frequency of the Hydroxy Group in Saturated Alcohols

A good linear relationship was found between the acid-induced ¹³C chemical shift change of the α-carbon atom and the OH stretching frequency of the hydroxy group in some saturated alcohols. The relationship is discussed with model calculations using the CNDO/2 method.

The trifluoroacetic acid-induced ¹³C chemical shift change in the α-carbon atom to the hydroxy group, Δδ¹³c, has been measured for a number, of saturated alcohols in carbon tetrachloride solution and provides information on the relative basicity and its dependence on the structural factor.¹ The free OH stretching frequency, v_OHis known to depend on the structural factor of the substituent._2–5 We reported that a linear relationship exists between the ¹⁷ O chemical shift, δ¹⁷ O, and the OH stretching frequency of the hydroxy group in saturated alchohols, R-OH.⁵ In this case, the ¹⁷O chemical shift change was reported to be governed by the ionization potential.⁶ The ionization potential of R-OH is expected to be correlated with its basicity. Regression analysis for Δδ¹³C was thus carried out for Δδ¹⁷OH reported for 14 and 19 typical alcohols, respectively. In order to explain the experimental results the oretically, we carried out CNDO/2 calculations for a series of methyl-substituted methanols.     

Calculation of the Parameters of a One‐Coordinate Model of the VGaSAs and VGaSnGa Complexes in Gallium Arsenide

Experimental optical bands of the emitting complexes (a gallium vacancy with a donor at the nearest, from the vacancy, sublattice site) V_GaS_As and V_GaSn_Ga in GaAs are investigated in a wide temperature range. The parameters of a onecoordinate model of these centers are determined. A configurationcoordinate diagram of the V_GaS_As complex is constructed. Calculation of the field dependences of emission rates is carried out in terms of the parameters of the onecoordinate model of the V_GaS_As complex and the data obtained are compared with the results of experimental studies of the emission of electron holes from a deeplying center of the V_GaS_As complex.     

Intramolecular 1,3-dipolar cycloaddition reactions in the synthesis of complex annelated quinolines, α-carbolines and coumarins

In this study, we report the synthesis of several novel dihydroisoxazole-, tetrahydroisoxazole- and dihydropyrazole-fused pyrido[2,3-b]quinolines, α-carbolines, and pyrido[2,3-c]coumarins, respectively, from simple precursors and by exploring intramolecular 1,3-dipolar cycloaddition reactions involving nitrile oxides, nitrones, and nitrile imines as 1,3-dipoles.     

Hydrogen Atom and Equivalent Form of the Lévy-Leblond Equation

We discuss the equivalent form of the Lévy-Leblond equation such that the nilpotent matrices are two-dimensional.We show that this equation can be obtained in the non-relativistic limit of the(2+1)-dimensional Dirac equation.Furthermore, we analyze the case with four-dimensional matrices, propose a Hamiltonian for the equation in(3+1) dimensions, and solve it for a Coulomb potential. The quantized energy levels for the hydrogen atom are obtained, and the result is consistent with the non-relativistic quantum mechanics.     

Coupled—Channel Investigation of Collisions of Protons and Antiprotons with Hydrogen Atoms in the 2p States

The impact parameter method is used to calculate the inelastic scattering cross sections of protons and antiprotons,which raise hydrogen atoms from the 2p states to the n=3 states.The calculation involves the n=1,2,3 states of the target and covers the energy range from 3keV to 2500keV.The study of the influence of the sign of the projectile charge is the main target of this investigation.Therefore,the exchange effects in the case of proton-induced reactions are ignored.The results of the calculations are in reasonable agreement with a previous work.     

Hydrogen in semiconductors: The roles of μSR and theory

Hydrogen is an unavoidable impurity in all semiconductors. It interacts with intrinsic defects (from monovacancies to dislocations), with impurities (shallow dopants, deep centers, even electrically inactive impurities), with the crystal, and with otherH interstitials. These interactions profoundly affect the electrical and optical properties of the host. Conventional experimental techniques used to study the properties of hydrogen (EPR, IR or Raman spectroscopy, etc.) have provided information on a number ofH-related defects. Theory has played a major role in these studies, not only by confirming the models proposed on the basis of experimental data, but often by explaining the data altogether or predicting new features. So far,SR has provided fundamental information on isolated hydrogen-like species in many semiconductors. It would be wonderful if thespectroscopic signature of muonium-impurity pairs could be identified or ifquantitative information regarding the stability of the various charge states of muonium could be obtained.     

Kinetics of Photogel Formation in Anthracene‐Containing Copolymers in the Presence of Singlet‐Excitation Energy Acceptors

We suggest a technique to control the rate of photocrosslinking fluorescent polymers by introducing a consumable acceptor of the energy of singlet excitation. We have constructed a model of the processes occurring in a layer of a photocrosslinking anthracenecontaining copolymer with the addition of the acceptor which is spent in the reaction of photooxidation by oxygen of the air and the algorithm for calculating the curves of gel formation in the presence of the acceptor. Comparison of the experimental kinetics of the depletion of the acceptor and accumulation of a gel in a layer with the data of model calculations has proved their good agreement. The possibility of increasing the contrast coefficient of the characteristic curve of negative photoresists on the basis of fluorescent photocrosslinked polymers with the aid of singlet excitation energy acceptors is demonstrated.     

Kinetics of the Processes of the Change in the Concentration of Photosensitive Paramagnetic Centers on Excitation and De‐Excitation of ZnCdS Single Crystals

The EPR technique is used to study the behavior of photosensitive paramagnetic centers (PPC) in zinc sulfidebased single crystals under different conditions of excitation by UV radiation.     

Formation of Color Centers and Molecular Complexes with a Weak Hydrogen Bond in Lithium Fluoride Crystals Depending on the Form of OH<Superscript>¯</Superscript> Inclusion

The form of oxygen-containing inclusions in the LiF crystal was shown to be determined by the laws of isomorphic substitution and impurity accumulation in a melt during crystal growth in open air. Color centers and hydrogen-bonded complexes of different types appear in the LiF crystal after irradiation depending on the form of OH^– and Mg²⁺ inclusions. The radiative decay of OH^– ions and the properties of molecular complexes (MCs) with a weak hydrogen bond are responsible for the decreased efficiency of formation of the F- and F₂-color centers and increased concentration of the positively charged F ₂ ⁺ - and F ₃ ⁺ -centers. Radiochemical reactions involving hydrogen and fluorine atoms and ions that compete with the formation of color centers were presented.