Cut-off wavelength

Very promising indeed is the ternary compound AlGaN. By shifting the Al/Ga ratio its spectral sensitivity can be tailored. The cut-off wavelength can be shifted between 380 nm and 310 nm [3]. Quantum efficiencies up to 50% have been obtained for SiC as well as for GaN, which is similar to the UV sensitivity of UV-en-hanced Si photodiodes. 

In summary, the use of RPLC is ideal for pharmaceutical analyses because of the broad range of commercially available stationary phases because the most common RPLC mobile phases (buffers with acetonitrile or methanol) have low UV cut-off wavelengths, which facilitate high sensitivity detection for quantitation of low-level impurities and because selectivity can readily be controlled via mobile phase optimization. Additionally, the samples generated for selectivity screening (as detailed above) are typically aqueous based. In subsequent phases of pharmaceutical development, aqueous-based sample solvents are ideal for sample preparation and are, under limited constraints, compatible with MS detection required to identify impurities and degradation products. 

Since photon energies decrease with increasing wavelength, there will be a maximnm wavelength beyond which the photons lack sufficient energy to canse electron transitions into the condnction band, known as the cut-off wavelength, Ag... 

Solvent Eluent strength Dielectric constant (Debye) Viscosity at20"C (cP) Refraictive inde x at 20"C Cut-off wavelength (nm)... 

The easy handling of water- and air-stable ILs also enables their application to spectroscopic measurements. ILs have good solvahng properties and a high spectral transparency (the UV cut off wavelength of alkylimidazolium-based... 

A full response in the UV and vacuum UV is accessible only with detectors fitted with special fluoride windows. The cut-off wavelengths of optical glass (g) and of silica (q) are shown in Figure 7.25. For some special applications windowless detectors are used and the sensitivity is then greatly extended in the vacuum UV region and beyond. 

Cyclobutenediones and N,N -dimethylaminoparanitroaniline are listed in Table I together with their Amax, molecular absorption coefficients (e) and SHG intensities in the relative scale to the urea. Visible spectra of cyclobutenedione 3 together with N,N -dimethylaminoparanitroaniline 6 in CH2CI2 are shown in Figure 1. It shows that Amax of cyclobutenedione 3 exists at the close position to the material 6 and shape of absorptions for cyclobutenedione 3 is rather sharper than nitro analogue 6, which reflects to the shorter cut off wavelength of the cyclobutenedione. 

The light generator is servo-controlled by the DSC software, which permits a choice of both light intensity and duration of the irradiation. The source can be filtered by sapphire disks in order to cut off wavelengths lower than 300 nm and thus to be representative of outdoor aging conditions. 

Other chromophores were also investigated this way, example includes cyclobutadiene based doped polymer, of about 8 pm V 1 d33 nonlinearity with about 10 wt % loading, for green 532 nm generation and poled pNAn-PVA for blue 443 nm generation, in this case below the 480 nm cut-off wavelength of the material [36,37]. 

The use of a grating to facilitate the out-coupling has been demonstrated [52]. In that work, a (methyl-3 -(p-nitro-phenyl)carbazate, MNCZ) crystal was used as the substrate with a slab transparent waveguide made of photoresist deposited on top. The grating coupler was fabricated holographically and the SHG of a Nd YAG 1.06 pm laser demonstrated. This nonlinear crystal has a nonlinear d36 coefficient of 22.7 pm V-1 (3 time larger than d24 of KTP) and a cut-off wavelength of 455 nm. Reported conversion efficiencies were at that time limited by lack of sufficient crystal flatness. 

Figure 12. Raman spectra of ethanol on quartz measured at various values of the angles of incidence and thus, various penetration depths. In addition the transmittance spectrum of the glass filter (OG515) is shown (causing the distortion of the spectrum to the left of the cut-off wavelength).

GaN/AlGaN heterostructures for solar-blind detectors have been grown by both RMBE and PMBE. By tuning the AIGaN bandgap the cut-off wavelength has been varied from 360 to 310 nm in p-i-n photovoltaic devices [72,73], Very competitive data were achieved, regarding the responsivity of 0.15 A/W and external quantum efficiencies of over 50%. 

Bandpass filters can be described in several ways. Most common is the Center Wavelength (CWL) and Full Width Half Maximum (FWHM) nomenclature, or alternatively, by nominal Cut-on and Cut-off wavelengths. In the former, the exciter in Fig. 2 is described as a 580/20 or, a filter with nominal CWL of 580 nm and a FWHM of 20 nm. The half maximum value is taken at the transmission value where the filter has reached 50% of its maximum value (Figure 3). In the latter scheme, the filter would be described as having a Cut-on of 570 nm and a Cut-off of 590 nm, no CWL is declared. The Cut-on describes... 

An UV/Vis spectrum of HS-polymer film with a thickness of 100 micrometers was studied by UV/Vis spectrophotometer, and result is shown in Fig. 6. The fihn does not show absorption in the range of 400-800nm, and cut off wavelength is 277nm. As a result, HS-polymer fihn has high transparency. 

Gordon R, Brolo AG (2005) Increased cut-off wavelength for a subwavelength hole in a real metal. Opt Express 13 1933-1938... 

The level of stray light should be assessed since it increases with instrument age. The British Pharmacopoeia (1980) requires that the absorbance at 200 nm of a 1.2% w/v solution of potassium chloride should exceed 2 absorbance units with respect to water as reference. Alternatively a glass Vycor filter can be used, since its absorption increases sharply at the cut-off wavelength of 210 nm any reading below this is attributable to stray light. The United States Pharmacopeial Convention... 

Fig. 25.5. Detection scheme for imaging labeled enzymes and multilayers simultaneously. Shown are the steady state absorption dashed line) and emission solid line) spectra for DiO light grey) and PDI dark gray). The excitation wavelengths used for each dye are indicated by arrows at the bottom. The best ratio of detected emission from the layers and from the enzyme molecules was accomplished by the use of an appropriate long pass cut-off filter (cut-off wavelength indicated)...

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