Optical frequency standard based on coherent population trapping resonance

We propose a new optical frequency standard, based on a coherent population trapping resonance. Such standard is a self-mode locking laser, pulse repetition frequency of which is directly locked to microwave clock-transition—the transition between the hyperfine ground state components of alkali atom. The unique properties of this standard result in reduction of the light shift which is the main reason limiting frequency stability of this standard.     

Inhibition of explosive decomposition of acetylene

An experimental study of the inhibition of the exothermic decomposition of acetylene diluted with household propane+butane mixture and hydrogen was performed. Acetylene-inhibitor mixtures were heated behind reflected shock waves. The shock wave was generated by the detonation wave initiated in a stoichiometric acetylene-oxygen mixture. The minimum volumetric inhibitor concentrations capable of suppressing the self-decomposition of acetylene were determined.     

Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films

Temperature-and magnetic-field-dependent measurements of the resistance of ultrathin superconducting TiN films are presented. The analysis of the temperature dependence of the zero-field resistance indicates an underlying insulating behavior, when the contribution of Aslamazov-Larkin fluctuations is taken into account. This demonstrates the possibility of the coexistence of the superconducting and insulating phases and of a direct transition from the one to the other. The scaling behavior of magnetic field data is in accordance with a superconductor-insulator transition (SIT) driven by quantum phase fluctuations in two-dimensional superconductor. The temperature dependence of the isomagnetic resistance data on the high-field side of the SIT has been analyzed, and the presence of an insulating phase is confirmed. A transition from the insulating to a metallic phase is found at high magnetic fields, where the zero-temperature asymptotic value of the resistance is equal to h/e².     

The Brillouin-Wigner expansion in a relativistic two-body formalism

The Brillouin-Wigner perturbation theory is used to precisely calculate the energy levels of hydrogen-like systems.     

Experimental measurement of the van der Waals binding energy of X-O2 clusters (X=Xe, CH3I, C3H6, C6H12)

Van der Waals binding energies for the X-O(2) complexes (X=Xe, CH(3)I, C(3)H(6), C(6)H(12)) are determined by analysis of experimental velocity map imaging data for O((3)P(2)) atoms arising from UV-photodissociation of the complex [A. V. Baklanov et al., J. Chem. Phys. 126, 124316 (2007)]. Several dissociation pathways have been observed, we focus on the channel corresponding to prompt dissociation of X-O(2) into X+2O((3)P) fragments, which is present for complexes of O(2) with all partners X. Our method is based on analysis of the kinetic energy of all three photofragments, where the O atom kinetic energy was directly measured in the experiment and the kinetic energy of the X partner was calculated using momentum conservation, along with the measured angular anisotropy for O atom recoil. We exploit the fact that the clusters are all T-shaped or nearly T-shaped, which we also confirm by ab initio calculations, along with knowledge of the transition dipole governing radiative absorption by the complex. The effect of partitioning the kinetic energy between translation along the X-O(2) and O-O coordinates on the angular anisotropy of the O atom recoil direction is discussed. Van der Waals binding energies of 110±20 cm(-1), 280±20 cm(-1), 135±30 cm(-1), and 585±20 cm(-1) are determined for Xe-O(2), CH(3)I-O(2), C(3)H(6)-O(2), and C(6)H(12)-O(2) clusters, respectively.     

Controlled hydrothermal growth of ZnO nanostructures by sequestering the Zn metal ions with the chelating agent EDTA

In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn²⁺ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm.     

Resonant light absorption by the ordered structures of ions stored in a trap

Far-infrared laser action has been demonstrated in three previously unknown laser media. The substances used were: propargyl fluoride, 15-N cyanogen fluoride, and hydroxylamine. Assignments of the molecular transitions giving rise to the observed laser lines were made for the latter two compounds.New FIR laser lines were also observed with two substances, vinyl chloride and vinyl fluoride, which were already known as laser media by pumping with isotopic CO₂ and N₂O laser lines.The wavelengths of a total of 26 new FIR laser lines were determined together with the threshold pump power and an indication of the relative line strengths.     

Power resonances in a Raman gas laser

The observation of a new type of resonance due to double-quantum transitions in the standing-wave field of a Raman gas laser is reported. A resonance dip with a width equal to that of the optically forbidden transition was experimentally detected in the output-vs-timing curve of a Raman Ne laser (λ=1.15 m) upon pumping by radiation of a He−Ne laser at 1.52 m. The theory presented shows that the resonance arises in the third order of perturbation theory when in resonant SRS the line is inhomogeneously broadened. The resonance can be considered as resulting from the overlap of dips in the velocity distribution of the nonlinear polarization induced by the standing laser wave.