Elastic backward scattering of negative pions on protons at 25 and 38 GeV/c

The backward elastic scattering reaction π^?p → pπ^? at momenta 25 and 38 GeV/c have been measured using a magnetic spectrometer with hybrid chambers. The experimental data on the dependence of the cross section dσ/du on the momentum transfer u as well as the energy dependence dσ/du at u = 0 are given.     

Polarization of radiation of distributed-feedback dye lasers with one- and two-component gain media

Polarization of the radiation generated by a distributed-feedback laser on one-component solutions and binary mixtures of coumarin dyes is investigated. It is established that, with a marked excess of the generation threshold, the degree of polarization P of the radiation generated by one-component solutions is practically independent of the wavelength. For binary mixtures, the spectral behavior of P depends on the donorlacceptor concentration ratio. Here, with the anisotropy of the distribution of excited molecules being partially disrupted in the process of energy transfer (from the donor to the acceptor), the degree of polarization decreases appreciably when radiation frequency is tuned from the short-wavelength region to the long-wavelength one. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 340–343, May–June, 2000.     

Pulse sequences for realizing the quantum Fourier transform on multilevel systems

Sequences of selective pulses of an RF magnetic field for realizing the quantum Fourier transform by NMR methods on systems with four, six, and eight nonequidistant levels are found using the virtual spin formalism. The results can be applied to other quantum systems when laser pulses are used.     

Brightness through Local Constraint—LNA‐Enhanced FIT Hybridization Probes for In Vivo Ribonucleotide Particle Tracking

Imaging the dynamics of RNA in living cells is usually performed by means of transgenic approaches that require modification of RNA targets and cells. Fluorogenic hybridization probes would also allow the analysis of wild‐type organisms. We developed nuclease‐resistant DNA forced intercalation (FIT) probes that combine the high enhancement of fluorescence upon hybridization with the high brightness required to allow tracking of individual ribonucleotide particles (RNPs). In our design, a single thiazole orange (TO) intercalator dye is linked as a nucleobase surrogate and an adjacent locked nucleic acid (LNA) unit serves to introduce a local constraint. This closes fluorescence decay channels and thereby increases the brightness of the probe–target duplexes. As few as two probes were sufficient to enable the tracking of oskar mRNPs in wild‐type living Drosophila melanogaster oocytes.     

Elastic backward scattering of negative pions on neutrons at 23 and 40 GeV/c

The differential cross sections of the elastic backward scattering reaction π⁻n→nπ⁻ has been measured at 23 and 40 GeV/c in the u-interval −0.07 ? u ? 0.01 (GeV/c)².     

Formation of mixed d- and f-block metal clusters in inert matrices: comparison of the observed and theoretical optical spectra of AgHo

The UV visible spectra obtained after simultaneous cocondensation of silver and holmium atoms with argon matrices at 9 K have been studied in the 200-800 nm region. While no new feature can be observed upon deposition, selective irradiation into both silver or holmium atomic absorptions results in growth of a new band at 430 nm, associated with formation of a mixed silver holmium species, tentatively assigned as AgHo. To support the assignment of the observed bands ab initio quantum chemical calculations were carried out for the dinuclear and trinuclear silver and holmium species, using pseudopotential approaches. Results for the electronic excitation energies and corresponding transition dipole moments for the diatomic molecules Ag2, Ho2, AgHo provide evidence that the 430 nm band should be attributed to the mixed cluster AgHo (theoretical band position at 436 nm), while the doublets at 498/504 and 558/563 nm belong to the homonuclear species Ho2 (theoretical values are at 482 and 562 nm). First conclusions are drawn with respect to the formation of the metal trimers Ho3, Ag2Ho, AgHo2.     

The equilibrium structures of the Li[C<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>]<Subscript>1</Subscript> (<Emphasis Type="Italic">n</Emphasis> = 7–12) complexes and their alternation depending on <Emphasis Type="Italic">n</Emphasis>

The equilibrium geometric configurations of the Li[C _n ]₁ (n = 7–12) complexes, where [C _n ]₁ is a cylindrical hydrocarbon containing the simplest zigzag nanotube fragment, were determined by the density functional theory method with the PBE0 exchange-correlation functional. Analytic molecular orbital (MO) estimates were obtained for isolated [C _n ]₁ hydrocarbons in the Hückel approximation. The appearance of nonbonding MOs for hydrocarbons with even n was demonstrated. Equilibrium structure types were found to alternate as n increased. This alternation correlated with the behavior of the frontier orbitals of the [C _n ]₁ hydrocarbon. At odd n, the Li atom was situated near the boundary of the π electron density of the bracelet, and the complex had C _s symmetry. Complexes with even n had the C _2v point group, and lithium was situated in the inner cylinder cavity above the center of one of benzene rings.