Red Laser Line Research Articles

In situ surface-enhanced Raman scattering investigation of poly(5-amino-1,4-naphthoquinone) using roughened electrodes and metal colloids

Electropolymerization of 5-amino-1,4-naphthoquinone on electrochemically roughened gold electrode has been performed by anodic oxidation of the monomer in CH3CN+0.1M LiClO4 electrolytic medium. The cyclic voltammograms recorded during the first stages of electropolymerization clearly demonstrate the competition between the oxidation reactions of the monomer and the working electrode. Thanks to the surface asperities of the roughened electrode and to gold particles embedded within the inner layers of the polymer, the Raman analyses with red laser line led to the observation of surface-enhanced Raman scattering effect. The in situ SERS spectra of poly(5-amino-1,4-naphthoquinone) obtained during the gradual variation of the electrode potential between the reduced and the oxidized states in both directions in CH3CN+LiClO4 medium confirmed the electroactivity and electrochemical stability of the polymer during the doping-undoping process, as well as the reversibility of the transition between the oxidized (CO) and reduced (CO−⋯Li+) forms of the quinone groups. Moreover, SERS analyses were also carried out using metal colloids. In this case, despite the very low polymer concentration (traces) and the mild experimental conditions (weak laser power) used in these experiments, a large amplification of the Raman signal took place. Thanks to the suspension of silver or gold particles, the polymer displays a SERS effect, which greatly improves the signal-to-noise ratio of the Raman spectra, thus allowing to perform a much better vibrational analysis and to determine the orientation and the fixation mode of the polymer on the metal surface.

Self-Diffusion and Constraint Release in Isotropic Entangled Rod–Coil Block Copolymers

Understanding dynamic relaxation mechanisms in self-diffusion and constraint release processes of rod–coil block copolymers is important for many technological applications that employ neat melts or concentrated solutions. Using a model system composed of poly(alkoxyphenylenevinylene) rods and polyisoprene coils, reptation theories of entangled rod–coil block copolymers are investigated in the isotropic melt state. Self-diffusion was measured by forced Rayleigh scattering using a red laser line and a new blue photoswitchable dye that allow operation above the bandgap of most semiconducting polymers. In contrast to previous tracer studies where the diffusion of rod–coils through a coil homopolymer matrix is slowed relative to coil homopolymers because of a mismatch in the curvature of the rod and coil entanglement tubes, slowed diffusion is only present in self-diffusion measurements above a critical molecular weight. An activated reptation mechanism with constraint release is proposed as a modification to...

Visual Target Localization, the Effect of Allocentric Audiovisual Reference Frame

Visual allocentric references frames (contextual cues) affect visual space perception (Diedrichsen et al., 2004; Walter et al., 2006). On the other hand, experiments have shown a change of visual perception induced by binaural stimuli (Chandler, 1961; Carlile et al., 2001). In the present study we investigate the effect of visual and audiovisual allocentred reference frame on visual localization and straight ahead pointing. Participant faced a black part-spherical screen (92cm radius). The head was maintained aligned with the body. Participant wore headphone and a glove with motion capture markers. A red laser point was displayed straight ahead as fixation point. The visual target was a 100ms green laser point. After a short delay, the green laser reappeared and participant had to localize target with a trackball. Straight ahead blind pointing was required before and after series of 48 trials. Visual part of the bimodal allocentred reference frame was provided by a vertical red laser line (15° left or 15°...

Multiplex Quantitative Competitive Polymerase Chain Reaction Based on a Multianalyte Hybridization Assay Performed on Spectrally Encoded Microspheres

Quantitative polymerase chain reaction (PCR) may be performed by two general approaches, namely, real-time PCR and quantitative competitive PCR (QC-PCR). QC-PCR makes use of the concept of a DNA competitor, which is the "gold standard" approach to circumvent the problem of the variation of amplification efficiency. However, QC-PCR in its classical form is a low-throughput method since it requires titration of each sample with the competitor followed by electrophoresis. The throughput of QC-PCR has been improved by capillary electrophoresis and microtiter well-based hybridization assays. The present work introduces a multiplex QC-PCR method, which is based on a multianalyte hybridization assay that is performed on spectrally encoded microspheres. The DNA competitors use the same primers and have equal size with their corresponding target DNA sequences but differ in a short (24 bp) centrally located sequence. Following multiplex PCR, biotinylated amplification products from all DNA targets and competitors are heat-denatured and hybridized with oligonucleotide probes, which are attached to addressable sets of fluorescent microspheres. The hybrids react with a streptavidin-phycoerythrin conjugate. The microspheres are then analyzed by flow cytometry employing two lasers. A red laser line is used for classification of the microspheres, and a green line excites phycoerythrin, whose fluorescence is related to the concentration of the analyte DNA. As a model, we have developed a multiplex quantitative competitive PCR assay for four targets. The amplification products from targets and competitors (a total of 8 DNA fragments) are determined simultaneously by the multianalyte hybridization assay. The limits of quantification for the hybridization assay of all amplified DNA fragments are below 13 pM. The multiplex quantitative competitive PCR assay detects approximately 500 copies from each target DNA. To our knowledge, the proposed method is the only approach to quantitative PCR that offers such a high potential for multiplexing.

Raman scattering inβ-ZnS

The first- and second-order Raman spectra of cubic ZnS $(\ensuremath{\beta}$-ZnS, zinc-blende) are revisited. We consider spectra measured with two laser lines for samples with different isotopic compositions, aiming at a definitive assignment of the observed Raman features and the mechanisms which determine the linewidth of the first order TO and LO Raman phonons. For this purpose, the dependence of the observed spectra on temperature and pressure is investigated. The linewidth of the TO phonons is found to vary strongly with pressure and isotopic masses. Pressure runs, up to 15 GPa, were performed at 16 K and 300 K. Whereas well-defined TO Raman phonons were observed at low temperature in the whole pressure range, at 300 K the TO phonons appear to hybridize strongly with the two-phonon background and lose their identity, especially in the (3--10)-GPa region. The intensity of the TO phonons, which nearly vanishes when measured with a red laser line, is shown to result from a destructive interference of the amplitudes of the band-edge resonance and that of a background of opposite sign. The analysis of these effects is aided by calculations of the densities of one- and two-phonon states performed with the adiabatic bond charge model of the lattice dynamics.

Anti-Stokes emission in LaCl 3 doped with U 3+ and Pr 3+ ions

An efficient blue emission of Pr 3+ ions was observed in a LaCl 3:U 3+, Pr 3+ crystal after direct excitation of the U 3+ ions by a red laser line. Evidence of up-conversion in U 3+ ions is shown. The phenomena observed are discussed in terms of cross-relaxation, successive absorption and up-conversion processes.

Low temperature phonon and X-ray photoelectron spectra of a c-axis oriented YBa 2Cu 3O 6.9 thin film

The temperature dependence of the 340 cm −1 phonon frequency and linewidth has been measured for the exciting red laser line at 1.834 eV and shows anomalies below T c. In the O 1s XPS spectrum a new peak occurs at 534 eV when T reaches 110K.

Measurement of an Optical Frequency and the Speed of Light

We report the measurement of the frequency of the 633-nm red laser line. This is the first measurement of an optical frequency in the visible range without reference to the speed of light or to a measured wavelength. Combination of the optical frequency with the known wavelength yields $c$ to an accuracy higher than previously known. This method demonstrates the practicability of a single-standard time-length measurement system unified via a defined value of the speed of light.

New O II 6640-Å laser line

A prominent red laser line has been observed in oxygen and air at a wavelength of 6640.2 ± 1 Å. This line corresponds to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3p^{2}S\min{1/2}\max{0}-3s^{2}P_{1/2}</tex> at 6640.90 Å of the O II spectrum. It is the strongest member of the observed emission lines close to the laser line.