Favorable Wavelength Research Articles

A spectroscopic study of the best pump wavelength in the 800 nm band for erbium-doped fluorozirconate fibre amplifiers

The fluorescence spectrum of erbium-doped fluorozirconate glass was investigated with a tunable Ti-sapphire laser source operating in the 800 nm band. It was found that the green fluorescence (comprised of the 524 nm and 546 nm bands), which was due to pump excited state absorption, was always present along with the useful 1550 nm fluorescence band. However, the intensity of the 1550 nm signal was found to reach a maximum and the intensity ratio of the 1550 nm and 546 nm signals were also approaching a maximum when excited with the 801 nm wavelength. This was therefore considered to be a favourable pump wavelength for erbium-doped fluorozirconate fibre amplifiers.

KrF for Fusion: An Overview of Laser Issues

An overview of KrF laser issues for fusion in the laboratory environment is presented. In this fusion method, lasers are used to compress the deuterium-tritium fuel in the pellet to several thousand times its initial density. Krypton-fluoride lasers offer favorable wavelength, bandwidth, pulse-shaping, efficiency, and high-repetition rate properties for achieving fusion. Large-scale demonstration plants for fusion, however, rely on the improvement or resolution of significant issues: front-end capabilities, amplifiers and amplifier scaling, optical engineering for the ultraviolet, alignment systems, kinetics, beam quality, target coupling, cost, and overall system factors. The authors feel that KrF lasers may be able to meet the required inertial confinement fusion driver characteristics, driver-target coupling particularities, and capsule physics issues necessary to produce net energy release from the fusion reaction.

Syntheses and Characteristics of Infrared Absorbing 2:1 Nickel Complex Dyes

Some 2:1 nickel complex infrared absorbing dyes were synthesized by the reaction of phenylenediamines, 2-aminobenzenethiols and 2-aminobenzene-selenols with nickel(II) chloride. These dyes generally absorbed infrared light over 860 nm, but those from phenylenediamines absorbed at 780–800 nm, which is the most favorable wavelength region for semiconductor laser optical recording dye medium. Introduction of alkyi and/or amino groups into the parent dye greatly improved the solubility in organic solvent and these dyes could be applied by the wet coating method to prepare dye medium.

A new sensing material for optical oxygen measurement, with the indicator embedded in an aqueous phase

A new type of oxygen-sensitive material is obtained by preparing an aqueous emulsion of a solution of an oxygen-sensitive fluorescent dye in a rigid polymer. The fluorescence of this emulsion is related to the oxygen partial pressure, but a Stern-Volmer plot is not linear over the whole pressure range. Aside from high sensitivity and specificity for oxygen, this new type of sensing material has favorable analytical wavelengths allowing the use of low-cost opto-electronic equipment. Since the indicator is embedded in an aqueous environment, the sensor should be capable of monitoring various kinds of reactions occurring in the aqueous phase, for instance enzymatic reactions which are accompanied by production or consumption of oxygen.

Design of a 13% efficient n-GaAs1−xPx semiconductor–liquid junction solar cell

We report here the design of the most efficient non-aqueous semiconductor–liquid junction solar cell studied to date. Our approach involves the use of ternary semiconductor electrodes made from solid solutions of a large hand gap material, GaP, and a small band gap material, GaAs. We demonstrate here that photoanodes consisting of such materials are capable of simultaneously yielding high open circuit voltages and favourable wavelength response to the solar spectrum. A few n-type semiconductor–liquid junction solar cells in aqueous solutions have been reported to yield high (>10%) solar-to-electrical conversion efficiencies1–3. However, for most materials, rapid photoanodic corrosion dominates the interfacial photochemistry4–8. Non-aqueous solvent systems can suppress electrode decay due to corrosion4,7,8; but modest (<6%) conversion efficiencies have been observed for all photoanodes studied in solar irradiation conditions9–13. The photoanodes used here yield over 13% solar-to-electrical conversion efficiencies, or more than double the efficiency of any other non-aqueous semiconductor–liquid junction solar cell previously reported.

Most suitable conditions for aerosol monitoring from space

Numerical modelling is used to search for the most suitable conditions, with the object of determining the atmospheric turbidity (aerosol optical depth) from upward emerging spectral radiances in cloudfree pixels over water surfaces. The most suitable conditions are those where the influence of the turbidity on the radiance most strongly outweighs that of the other optically acting constituents. Since the actual values of these constituents of atmosphere and surface are usually known only within certain limits, using the most suitable conditions minimizes the uncertainty in the turbidity to be derived from satellite measurements. As a result, favorable zenith angles of the satellite and favorable wavelengths are presented for an atmosphere with maritime aerosols with and without Saharan dust. The results represent an advance on a paper published by the authors in 1981 [1].

Rapid and sensitive high-resolution procedure for digitalis glycoside analysis by derivatization liquid chromatography

The separation and quantitative determination of digitalis glycosides by high-performance liquid chromatography following derivatization with 4-nitrobenzoyl-chloride (4-NBCl) is described. The compounds of primary interest were the digitalis glycosides and aglycones of the pharmaceutically important A, B and C series. The derivatization step results in higher extinction values at a more favourable wavelength (260 nm), which permits the use of low-cost ultraviolet detectors. Detection limits are below 20 ng/ml for all of the glycosides tested. The chromatographic properties are also improved by reducing the polarity without a decrease in selectivity. The use of low-polarity and low-viscosity solvent systems on silica gel adsorbents permits rapid isocratic separations of complex mixtures as they usually occur in pharmaceutical products and extracts. The quantitative potential of this method was demonstrated by analyzing ampoule solutions containing desacetyl lanatoside C as the active compound. The active substance, by-products and degradation products were determined down to 0.1% of the total glycoside concentration in one ampoule.

Calibrated remote measurements of SO2 and O3 using atmospheric backscatter

Remote measurements of calibrated samples of SO2 and O3 have been achieved with a lidar using ultraviolet signals produced by a tunable dye laser and a nonlinear crystal. The operating wavelengths for these measurements were 292.3 and 293.3 nm for SO2 and 292.3 and 294.0 nm for O3. The atmosphere in front of and behind the chamber acted as a distributed reflector to send laser light back through the chamber to a receiver near the laser. The laser measurements agreed well with in situ measurements. Integration of eight laser pulses at each of two wavelengths allowed the determination of SO2 concentration with an uncertainty equivalent to ±0.6 ppm in 100 m for low concentrations. For O3, the corresponding uncertainty limit was ±1.2 ppm in 100 m. The measurement errors are primarily attributable to variations in atmospheric backscattering intensity during the experiment, since the different wavelengths were radiated sequentially rather than simultaneously. The sensitivity of a system transmitting more favorable wavelengths at intervals separated by less than 1 min is estimated to be near ±0.1 ppm in 100 m for both SO2 and O3.

Physical Conditions in the Nucleus of M82

view Abstract Citations (64) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Physical Conditions in the Nucleus of M82 Peimbert, Manuel ; Spinrad, Hyron Abstract Narrow-band photoelectric photometry of the nucleus and a bright region northeast of the center of M82 was carried out with the 120-inch telescope at Lick Observatory. The intensity of several emission lines in the nucleus, as well as of the continuum in both regions at different wavelengths, was obtained. From the Balmer and Paschen emission lines of hydrogen, an interstellar absorption of 4.23 mag at Hfl was derived for the nucleus. Collisions by thermal electrons are not responsible for the ionization in the nuclear region: this result and the observed Balmer decrement led to the adoption of radiation as the principal mechanism of ionization. The thermal contribution to the radio flux is smaller than 10 percent in the most favorable wavelengths. By extrapolating the radio spectrum to below the Lyman limit on the basis of a model of a single electron reservoir, synchrotron radiation fails by at least two orders of magnitude for the excitation of Ha in the nucleus; furthermore, the synchrotron contribution to the visible region of the spectrum is negligible. The N(He+)/N(H+) ratio is 0.065; however, a large fraction of the helium atoms is neutral, and the N(He)/N(H) ratio is about 0.13. The observed Balmer jump is smaller in the nucleus than in the region northeast of it. It is found that the spectral type of the galaxy becomes progressively later from the center outward. Publication: The Astrophysical Journal Pub Date: May 1970 DOI: 10.1086/150444 Bibcode: 1970ApJ...160..429P full text sources ADS | data products SIMBAD (7) NED (1)

Physical Conditions in the Nuclei of M51 and M81

view Abstract Citations (164) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Physical Conditions in the Nuclei of M51 and M81 Peimbert, Manuel Abstract Narrow-band photoelectric photometry of the nuclei of M51 and M81 was carried out with the Crossley and the 120-inch telescopes at Lick Observatory. The intensity of several emission lines, as well as of the continuum at different wavelengths, was obtained. From the [0 i], [0 ii], and [0 iii] line inten- sities, it was found that collisions by thermal electrons are not responsible for the ionization in M81 and M51. This result7 coupled with the observed Balmer decrement in M81, led to the adoption of radiation as the principal mechanisn~ of ionization. The radiation field needed to explain the intensity of Ha in MM and M81 was computed for three black-body temperatures. The predicted contribution of such a radiation field to the integrated observed flux in the most favorable wavelengths of the visual region was found to be very small Large density fluctuations were found in the nuclei of M51 and M81 by comparing the Ne(A3727) density with the Ne(rms) density. From the intensity of the [0 i} X6300 line, it was found that a large fraction of the material in these nuclei is in the neutral form. Solar abundances cannot explain the relative line intensities in the nuclei of M51 and M81 Several arguments are presented which suggest an overabundance of nitrogen in the nuclei of both galaxies. From these arguments it was concluded that most of the variation of the N 11/Ha intensity ratio from the spiral arms to the nuclei of both galaxies is caused by a change of the nitrogen abundance and not by a change of electron temperature Publication: The Astrophysical Journal Pub Date: October 1968 DOI: 10.1086/149738 Bibcode: 1968ApJ...154...33P full text sources ADS | data products NED (3) SIMBAD (2)

Microwave Modulation of Light in Ferromagnetic Resonance

Direct spectroscopic evidence has been obtained of microwave sidebands imposed on a monochromatic light beam by transmission through a single crystal of chromium tribromide at ferromagnetic resonance. Microwave frequencies above 13.5 Gc/sec may be used, and the most favorable optical wavelengths for this effect lie between 4750 and 5000 Å. This work has demonstrated modulation of a 4810-Å beam by a 23.5-Gc/sec microwave signal. This paper discusses the conditions under which the modulation may be observed, and how some of these may be optimized.

Photometric Milk Fat Determination

Summary The theoretical consideration and practical application of a photometric procedure for milk fat determination are presented. The interfering turbidity due to casein micelles is eliminated chemically by use of a calcium chelating agent. Coherent scattering is eliminated by a fivefold dilution of milk samples. Using a favorable wave length of light, in the visible range, turbidity is measured as a function of average globule size for the size range of fat in homogenized milk. The two characteristics of the milk fat emulsion which then remain unalterably to influence the total scattering are fat content and average globule size. Two independent photometric measurements are required to solve for the two variables simultaneously. The parallel transmitted and the total transmitted light through a thin layer of the prepared sample constitute two independently variable intensities. Mathematical development of the problem led to two linear equations from which a nomogram can be constructed to read both fat content and average particle size. From photometric readings on known samples, a nomogram was drawn and the two characteristics read for a number of commercial milk samples. The results agree well with the Babcock comparative values. Applicability of the present method to other dairy products is discussed.

The Spectrum of γ Pegasi.

view Abstract Citations (14) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectrum of γ Pegasi. Underhill, Anne B. Abstract Two coudé plates of -y Pegasi have been measured for wave length, and some new lines were found. About 70 per cent of the 877 lines measured between X 3965 and X 4921 have been identified. The results show generally that the spectrum of any element of reasonably high abundance on the earth may be found if its excitation potential is around 20-25 volts. Potassium has not been found, in spite of the fact that it is abundant on the earth, and the lines of the Ku spectrum have very favorable wave length and excitation potential for appearance in ~y Pegasi. Small displacements, such as are qualitatively expected on the basis of Stark effect, are found for the He i lines. A quantitative comparison is made between theory and observation, and it is shown that the observed displacements of the diffuse-series lines are more nearly in agreement with those calculated by M. K. Krogdah.1 on the basis of collisional broadening than with those given by the theory of Stark effect from constant fields. Some forbidden He I lines of the 2'P - m'P series are tentatively identified, and a possible explana- tion of a small luminosity effect at X 4026 between dwarf and intermediate B-type stars is proffered Publication: The Astrophysical Journal Pub Date: May 1948 DOI: 10.1086/145017 Bibcode: 1948ApJ...107..337U full text sources ADS |

Transmission of Electric Waves Round the Bend of the Earth

I BEG leave to amend a sentence in my letter which appeared in NATURE of May 28. I wrote that the existence of a most favourable wave-length for transmission to a given distance appeared to be contradicted by the diffraction theory. A more leisurely study of Prof. MacDonald's paper shows me that I have in this respect misinterpreted his integrals, and that it is not impossible that the existence of an optimum wavelength may yet be explained by his analysis. This emendation in no way affects the table of ratios I gave or the wording of the conclusion drawn there from.

Transmission of Electric Waves Round the Bend of the Earth

I BEG leave to amend a sentence in my letter which appeared in NATURE of May 28. I wrote that the existence of a most favourable wave-length for transmission to a given distance appeared to be contradicted by the diffraction theory. A more leisurely study of Prof. MacDonald's paper shows me that I have in this respect misinterpreted his integrals, and that it is not impossible that the existence of an optimum wavelength may yet be explained by his analysis. This emendation in no way affects the table of ratios I gave or the wording of the conclusion drawn there from.