High resolution measurement and MQDT analysis of the 5d<Superscript>9</Superscript> 6s<Superscript>2</Superscript> np,nf (J = 1) autoionizing resonances of mercury

We report new high resolution photoabsorption measurements of the 5d-subshell excitation spectra of mercury using a 3-meter normal incidence spectrograph equipped with a 6000 line/mm holographic grating and synchrotron radiation emitted by the Bonn 2.5 GeV electron accelerator as the background source of continuum. The observed spectra reveal autoionizing resonances attached to the 5d⁹(²D_5/2)6s² and 5d⁹(²D_3/2)6s² parent ion levels of mercury. We have analysed the line shapes of the lower members of the 5d⁹6s² np and nf J = 1 autoionizing resonances using the phase shifted formulation of the MQDT and extracted the interaction parameters.     

External cavity tunable diode laser spectra of the ν1 + 2ν4 stretch-bend combination bands of NH3 and NH3

The ammonia ν₁ + 2ν₄ perpendicular stretch-bend combination band has been investigated in spectra of ¹⁴NH₃ and ¹⁵NH₃ recorded in the 6400-6800 cm⁻¹ region with an external cavity tunable diode laser (ECTDL) spectrometer. For ¹⁴NH₃, new assignments were determined initially by extrapolating from published low-J jet-cooled beam results up to transitions of higher J and K. Corresponding ν₁ + 2ν₄ transitions for the ¹⁵NH₃ species were then found by identifying similar patterns of lines with a characteristic downshift of approximately 9.7 cm⁻¹. Assignments were confirmed employing ground-state combination differences. Term values, a-s inversion splittings, l-doubling energies and parameter estimates from simple single-state fits are reported for the two ammonia species.     

Novel fluorescent N,O-chelated fluorine-boron benzamide complexes containing thiadiazoles: Synthesis and fluorescence characteristics

A series of N-(5-phenyl-1,3,4-thiadiazol-2-yl)benzamide derivatives and their corresponding BF₂ complexes were synthesized, and their photophysical properties were determined. The effect of the derivatives with various substituents on the benzamide ring and phenyl-1, 3, 4-thiadiazole ring were examined in different organic solvents and in the solid state. These dyes enjoy a series of excellent photophysical properties including the large Stokes shift, solid-state fluorescence, and aggregation-induced emission effect (AIEE).     

Can Variations of 1H NMR Chemical Shifts in Benzene Substituted with an Electron‐Accepting (NO2)/Donating (NH2) Group be Explained in Terms of Resonance Effects of Substituents?

The classical textbook explanation of variations of ¹H NMR chemical shifts in benzenes bearing an electron‐donating (NH₂) or an electron‐withdrawing (NO₂) group in terms of substituent resonance effects was examined by analyzing molecular orbital contributions to the total shielding. It was found that the π‐electronic system showed a more pronounced shielding effect on all ring hydrogen atoms, relative to benzene, irrespective of substituent +R/?R effects. For the latter, this was in contrast to the traditional explanations of downfield shift of nitrobenzene proton resonances, which were found to be determined by the σ‐electronic system and oxygen in‐plane lone pairs. In aniline, the +R effect of NH₂ group can be used to fully explain the upfield position of meta‐H signals and partly the upfield position of para‐H signals, the latter also being influenced by the σ‐system. The position of the lowest frequency signal of ortho‐Hs was fully determined by σ‐electrons.     

EXAFS study of intermetallics of the type RGe2 (R=La,Ce, Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Y) Part II: Determination of Ge-R distances

The extended x-ray absorption fine structure (EXAFS) associated with the GeK x-ray absorption discontinuity in pure germanium and in the intermetallics RGe₂ (R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been studied. The Ge-R distances in these compounds have been determined by comparing the experimental phase shifts with the theoretical ones. The Ge-R distances in the compounds TbGe₂, HoGe₂ and ErGe₂ are being reported for the first time in this work.     

Theoretical analysis of Resonant Auger Electron Spectra produced by isolated resonances

Summary  Line profiles of Resonant Auger Electron Spectra produced by isolated resonances are analyzed by separating the contributions due to the direct, resonant and interference terms and taking explicitly into account the effects due to the finite bandwidth of the incident radiation. The mean kinetic energy of the emitted electron and the spectral width of the Auger lines are also studied as functions of the parameters characteristic of the incident radiation. The general expressions derived by the theory are applied to the analysis of the lineshapes produced by a specific electronic transition taken from the autoionization spectrum of the CO molecule.     

Reasons for the variability of isotopic ratios of stretching vibration frequencies of H-bonded complexes

The effect of random resonances and vibration anharmonicity on the isotopic ratios of frequencies for molecules containing hydrogen atoms has been studied. It was found that the anomalous frequency dependence of the v(XH)/v(XD) isotopic ratio of the stretching vibration frequencies observed for H-bonded systems can be explained in terms of the theory of harmonic vibrations of molecules. The substantial deviation of experimental v(XH)/v(XD) from the magnitude equal to the square root of the reciprocal ratio of adjusted masses results from random resonances between the stretching mode of the bridging proton and some other vibration of the system.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2090–2097, December, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research, Project No. 94-03-09340.     

Some rigorous results for the Greenberg-Hastings Model

In this paper, we obtain some rigorous results for a cellular automaton known as the Greenberg-Hastings Model. The state space is {0, 1, 2}^{Z d} . The dynamics are deterministic and discrete time. A site which is 1 changes to 2, a site which is 2 changes to 0, and a site which is 0 changes to a 1 if one of its 2d neighbors is a 1. In one dimension, we compute the exact asymptotic rate at which the system dies out when started at random and compute the topological entropy. In two or more dimensions we show that starting from a nontrivial product measure, the limit exists as 3m and is Bernoulli shift. Finally, we investigate the behavior of the system on a large finite box.     

Hydrogen-bonded complexes involving HF and HCl: the effects of electron correlation and anharmonicity

Calculations on the hydrogen-bonded complexes HCNHF, H₂OHF, ClCNHCl and (CH₃)₂OHCl are reported. SCF harmonic values for the HF and HCl frequency shifts are in considerable disagreement with experiment, by as much as 100 cm^–1. Calculations at the MP2 (harmonic) level yield improved agreement with experiment, reducing discrepancies to the order of 10 cm^–1. We have also calculated all the cubic and quartic force constants for HCNHF at the SCF level, so that the anharmonic constants, x _rs can be evaluated. Although x ₁₁ (v ₁=H-F stretch) is large and negative, it is more than compensated by a positive x ₁₆ (v ₆=NH-F bend), so that the anharmonic correction to v ₁ is small and positive. The validity of these anharmonistudies is examined.