The conversion of infra-red radiation into visible in a proustite crystal when the pump beam and the infra-red signal beam are perpendicular to each other

The conversion is considered of infra-red radiation into visible in a proustite crystal with the pump and signal waves perpendicular to each other. The angular and spectral parameters as well as the efficiency of such interactions are determined.The advantages of this interaction are discussed.     

Nucleon-nucleon correlations in the (γ, π<Superscript>−</Superscript><Emphasis Type="Italic">p</Emphasis>) and (γ, π<Superscript>−</Superscript><Emphasis Type="Italic">pp</Emphasis>) reactions on the <Superscript>12</Superscript>C nucleus

The photoproduction of negative pions on the carbon nucleus in the (γ, π^?p) and (γ, π^?pp) reactions has been studied experimentally. The measurements are interpreted using a model of the formation of an intermediate Δ nuclear state (Δ nucleus) that decays with the emission of a pion and a nucleon.     

Forming stable nonlinear lightguides with cross-modulation self-locking of incoherent soliton modes

This paper discusses a new class of spatially localized soliton solutions with bounded energy in the problem of the nonlinear propagation of a light beam along a photorefractive crystal (PRC) with a drift mechanism of nonlinear response. Solitons of this class correspond to stable propagation in the PRC of two or more wave packets (components) that are matched in intensity distribution but incoherent. Their spatial distributions correspond to simultaneous cross-modulation self-locking of its first-and higher-order modes into the common nonlinear waveguide formed by them. It is shown that such multicomponent solitons can be implemented and that they are structurally stable both with respect to collisions and with respect to substantial (more than 10% in intensity) stochastic perturbations of their components as they propagate to distances of the order of several diffraction lengths. The paper discusses the possibility that conjugate polymers, antiferromagnets, and superconductors can contain unusual states corresponding to the stable propagation of two or more mutually incoherent but matched electron wave packets along conjugate chains or along isolated atomic planes. Zh. éksp. Teor. Fiz. 113, 1167–1180 (April 1998)     

Evidence for a quasi-two-dimensional proton glass state in Cs5H3(SO4)(4); xH(2)O Crystals

We describe damping of hypersonic and ultrasonic longitudinal acoustic (LA) phonons in crystals of Cs 5H (3)(SO (4))(4);xH 2O (PCHS) between 100 and 360 K. The damping of LA phonons exhibits strong dispersion caused by relaxation processes in the region of transformation into the glasslike phase (T(g) approximately 260 K). Near T(g) the damping of ultrasonic phonons propagating in the basal plane reflects the cooperative freezing of acid protons. The damping of LA phonons propagating perpendicular to the basal plane can be fit by the Debye model and is due to the interaction between protons and LA phonons. This suggests that the proton glass state that is realized at T相似文献   

Refinement of hydrogen positions in (NH4)2SeO4

The crystal structure of ammonium selenate has been studied by means of single crystal x-ray and neutron diffraction with the purpose of the refinement of hydrogen positions. The refined hydrogen positions obtained by single crystal neutron diffraction show that N-H bond lengths form a regular tetrahedron in an ammonium ion. The single crystal x-ray diffraction data show that N-H bond lengths are shorter than those obtained by neutron diffraction and are not equal between themselves. Thus, the comparison of the results of x-ray and neutron diffraction allows one to suggest that the shorter N-H bond lengths obtained by x-ray diffraction reflect the distribution of the electron charge density of ammonium ions within the (NH₄)₂SeO₄ crystal lattice. The text was submitted by the authors in English.     

P680 (P(D1)P(D2)) and Chl(D1) as alternative electron donors in photosystem II core complexes and isolated reaction centers

Low temperature (77-90 K) measurements of absorption spectral changes induced by red light illumination in isolated photosystem II (PSII) reaction centers (RCs, D1/D2/Cyt b559 complex) with different external acceptors and in PSII core complexes have shown that two different electron donors can alternatively function in PSII: chlorophyll (Chl) dimer P(680) absorbing at 684 nm and Chl monomer Chl(D1) absorbing at 674 nm. Under physiological conditions (278 K) transient absorption difference spectroscopy with 20-fs resolution was applied to study primary charge separation in spinach PSII core complexes excited at 710 nm. It was shown that the initial electron transfer reaction takes place with a time constant of ~0.9 ps. This kinetics was ascribed to charge separation between P(680)* and Chl(D1) absorbing at 670 nm accompanied by the formation of the primary charge-separated state P(680)(+)Chl(DI)(-), as indicated by 0.9-ps transient bleaching at 670 nm. The subsequent electron transfer from Chl(D1)(-) occurred within 13-14 ps and was accompanied by relaxation of the 670-nm band, bleaching of the Pheo(D1) Q(x) absorption band at 545 nm, and development of the anion-radical band of Pheo(D1)(-) at 450-460 nm, the latter two attributable to formation of the secondary radical pair P(680)(+)Pheo(D1)(-). The 14-ps relaxation of the 670-nm band was previously assigned to the Chl(D1) absorption in isolated PSII RCs [Shelaev, Gostev, Nadtochenko, Shkuropatov, Zabelin, Mamedov, Semenov, Sarkisov and Shuvalov, Photosynth. Res. 98 (2008) 95-103]. We suggest that the longer wavelength position of P(680) (near 680 nm) as a primary electron donor and the shorter wavelength position of Chl(D1) (near 670 nm) as a primary acceptor within the Q(y) transitions in RC allow an effective competition with an energy transfer and stabilization of separated charges. Although an alternative mechanism of charge separation with Chl(D1)* as the primary electron donor and Pheo(D1) as the primary acceptor cannot be ruled out, the 20-fs excitation at the far-red tail of the PSII core complex absorption spectrum at 710 nm appears to induce a transition to a low-energy state P(680)* with charge-transfer character (probably P(D1)(δ+)P(D2)(δ-)) which results in an effective electron transfer from P(680)* (the primary electron donor) to Chl(D1) as the intermediary acceptor.     

Influence of field ionization on the efficiency of neutron generation

The results of experiments on neutron generation caused by nanosecond discharges in a deuterium medium are presented. The experiments are performed using two types of potential electrodes (anodes). One of them is fabricated from steel foil, and the other is composed of tungsten wires with split ends. In both cases, a deuterium-saturated zirconium plate is employed as a flat grounded cathode. With a tungsten anode, deuterium ions generated by field ionization are demonstrated to constitute the determining part of ions involved in the acceleration process and the neutron yield arising from the reaction ²H(d, n)³He is about four times greater than that inherent to the steel-foil anode. In this case, the maximum neutron yield is 1.2 × 10⁴ neutron/ shot, and the duration of neutron emission from the cathode is 1.5 ns.