Gas‐phase tautomerism in 1‐phenylazonaphthalene‐4‐ol: verification of the responses of individual tautomers

Gas‐phase tautomerism in 1‐phenylazonaphthalene‐4‐ol (1) was studied by using electron ionization (EI) mass spectrometry on the basis of the fragmentations of the model enol and keto tautomers, where the movable proton is replaced by a methyl group. These fixed tautomers were obtained as an easy separable mixture by simple methylation of the cheap and easily accessible diazene (1). It was found that their EI mass spectral fragmentations are in full congruence with the already published theoretical predictions. The relative energies required for bond cleavage in 1 and its fixed tautomers were estimated by stepwise increasing of the electron energy of the ion source of the mass spectrometer. A simple equation for the approximate estimation of the molar fractions of the individual tautomers was suggested. It was shown that the enol form is dominant in the temperature range of 200–300°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Echo spectroscopy of a phase-sensitive thermostat

Kinetic equations describing the behavior of an atom in nonresonant classical and broadband squeezed fields are obtained. The two-pulse photon echo under the conditions of additional illumination by non-resonant fields is studied theoretically. It is shown that investigation of the photon echo decay allows one to determine the main parameters of the squeezed field.     

Impact of cavity symmetry on mode suppression and increase of free spectral range in solid-state dye microlaser

We describe modeling the solid-state dye laser with the microcavity size comparable to light wavelength.Certain symmetry in the allocation of gain material leads to depletion of odd longitudinal modes that,in turn, increases the tunability range of the microlaser. We provide simple physical explanation for the modeling results.     

Characterization of the bonding structure of nanocrystalline diamond and amorphous carbon films prepared by plasma assisted techniques

Thin nanocrystalline diamond/amorphous carbon (NCD/a-C) composite films and amorphous diamond-like carbon (DLC) films were prepared by three methods: microwave plasma chemical vapour deposition (MWCVD) from methane/nitrogen mixtures (NCD/a-C), RF magnetron sputtering of a pure graphite target in argon/methane ambients, and pulsed laser deposition (PLD) in vacuum or argon atmosphere (DLC). The films prepared by the three techniques were comprehensively characterized with respect to their bonding structure by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). PACS 81.05.Uw; 82.80.Pv     

Spectral kinetic properties of Yb3+:Na4Y6F22 and Yb3+:LiLuF4 crystals

Yb³⁺ (2.7 at.%):Na₄Y₆F₂₂ and Yb³⁺(1 at.%):LiLuF₄ crystals were grown by the Bridgman-Stockbarger method. We measured the temperature dependences of the thermal conductivity of the crystals and the absorption spectra. We determined the radiative lifetime of the Yb³⁺ ion in these crystals (1.94 msec and 2.13 msec) and calculated the stimulated emission cross section spectra. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 761–766, November–December, 2007.     

Coherent influence of RF field on the gamma-optical properties of a medium upon crossing-anticrossing of nuclear levels

A new approach to the observation of electromagnetic-induced transparency in gamma optics is proposed. For this purpose, the propagation of a resonant gamma photon in a ⁵⁷Fe magnetic medium affected by an external radiofrequency (RF) field is considered. It is demonstrated that, in the case of crossing-anticrossing, a resonant RF field significantly transforms gamma-optical properties of the medium that become dependent on its parameters. This allows coherent control of the group velocity of gamma photons and controlled filtering of unpolarized gamma radiation in the sample to be realized.     

Magnetic structure and magnetic excitations in the two-dimensional spin system of the Cu<Subscript>3</Subscript>B<Subscript>2</Subscript>O<Subscript>6</Subscript> compound

This paper reports on the results of measurements of the magnetic susceptibility, heat capacity, neutron scattering, muon spin relaxation, and electron paramagnetic resonance in Cu₃B₂O₆ for the study of the ground state of the spin system of this compound. The results obtained suggest that, at a temperature of 10 K, the spin subsystem of the crystal, which consists of single spins and clusters of pairs and fours of spins interacting with one another, undergoes a transition to a state representing a superposition of the singlet (for clusters) and magnetically ordered (for single spins) states.