Pion pair production in photon-photon collisions

The process γγ→π⁺π^? was measured using the detector MD-1 at VEPP-4. The two-photon reactionse ⁺ e ^?, μ⁺ μ^? and π⁺ π^? pair production were separated using scintillation counters, Cherenkov counters and shower-range chambers. A radiation widthГ _γγ(f ₂(1270))=3.1±0.35±0.35 keV was obtained.     

Anthra[1,2-b]furan and 1h-naphth[2, 3-g]indole derivatives

A number of previously inaccessible anthra[1,2-b]furan and 1H-naphth[2,3-g]indole derivatives were obtained by condensation of 1,4-anthraquinone with acetoacetic ester and its analogs. Quinones of the anthra[1,2-b]furan series were obtained by oxidation of the methoxy derivatives of anthra[1,2-b]furan.Translated from Khimiya Geterotsiklicheskikh Soedtaenii, No. 8, pp. 1027–1029, August, 1972.     

Laser-diode-pumped phosphosilicate-fiber Raman laser with an output power of 1 W at 1.48 mum

An all-fiber 1.48-mum generator based on a laser-diode-pumped Yb-doped double-clad laser and a cascaded Raman wavelength converter has been developed. Second-order Raman Stokes radiation was generated in a phosphosilicate-fiber resonator formed by two pairs of Bragg gratings. A slope efficiency of the Raman converter of 48% with respect to the power emitted by the double-clad Yb laser has been achieved. We obtained an output power of 1 W at a slope efficiency of 34% with respect to the laser-diode array power, with a total optical-to-optical efficiency of 23%.     

Heterodyne polarimetry for measuring critical dimensions on semiconductor wafers

A new optical technique based on heterodyne polarimetry is developed for fast measurement of critical dimensions on semiconductor wafers, particularly on those of memory chips. Sub-wavelength periodical structure of a sample acts as a wire-grid polarizer, making both the amplitude and phase of the reflected laser beam dependent on geometrical dimensions and optical properties of the wafer pattern. The heterodyne technology based on the cross-polarized two-frequency Zeeman laser is used to simultaneously measure the amplitude and the phase of the reflected laser beam. Very fast and efficient effective medium trapezoidal algorithm is developed for extracting values of critical dimension from the measurements. The technique is most suitable for inspection of multi-periodical patterns consisting of large number of periodically distributed small areas of sub-wavelength gratings. Theoretical background, simulation, and experimental results are presented.     

Studies of acylation kinetics of aspen wood with aromatic carboxylic acids

With the help of Erofeev-Kolmogorov and Eiring equations kinetic characteristics of acylation of the aspen wood with the aromatic carboxylic acids in presence of thionyl chloride in the trifluoroacetic acid medium were calculated and thermodynamic parameters of this process were established.     

Electron in the field of flexural vibrations of a membrane: Quantum time,magnetic oscillations,and coherence breaking

We have studied the motion of an electron in a membrane under the influence of flexural vibrations with a correlator that decreases upon an increase in the distance in accordance with the law r–^2η. We have conducted a detailed consideration of the case with η < 1/2, in which the perturbation theory is inapplicable, even for an arbitrarily weak interaction. It is shown that, in this case, reciprocal quantum time 1/τ_q is proportional to g^1/(1–η)T^{(2–η)/(2–2η)}, where g is the electron–phonon interaction constant and T is the temperature. The method developed here is applied for calculating the electron density of states in a magnetic field perpendicular to the membrane. In particular, it is shown that the Landau levels in the regime with ω_cτ_q » 1 have a Gaussian shape with a width that depends on the magnetic field as B^η. In addition, we calculate the time τ_φ of dephasing of the electron wave function that emerges due to the interaction with flexural phonons for η < 1/2. It has been shown that, in several temperature intervals, quantity 1/τ_φ can be expressed by various power functions of the electron–phonon interaction constant, temperature, and electron energy.     

Visualization of the surface roughness by x-ray scanning

In the x-ray region the reflectivity of a superpolished surface strongly depends on its roughness. This effect may be used to obtain a two-dimensional map of the roughness spatial distribution for flat surfaces with an average roughness height of the order of one nanometer or less. The method described in the paper lies in the illumination of the sample by a highly collimated x-ray beam, and a linear one-dimensional scanning of the sample with simultaneous registration of the specular component of the reflected beam by multielement linear detector. This method may be used to monitor the surface quality of silicon semiconductor wafers, computer hard disks, x-ray and laser mirror substrates etc.