Xenon maximum

A gun is used to direct a beam of fast-moving atoms or ions onto the liquid target (matrix). Figure 4.1 shows details of the operation of an atom gun. An inert gas is normally used for bombardment because it does not produce unwanted secondary species in the primary beam and avoids contaminating the gun and mass spectrometer. Helium, argon, and xenon have been used commonly, but the higher mass atoms are preferred for maximum yield of secondary ions. 

The efficiency of a helium—neon laser is improved by substituting helium-3 for helium-4, and its maximum gain curve can be shifted by varying the neon isotopic concentrations (4). More than 80 wavelengths have been reported for pulsed lasers and 24 for continuous-wave lasers using argon, krypton, and xenon lasing media (111) (see Lasers). 

High pressure xenon lamps are also employed in some TLC scanners (e.g. the scanner of Schoeffel and that of Farrand). They produce higher intensity radiation than do hydrogen or tungsten lamps. The maximum intensity of the radiation emitted lies between k = 500 and 700 nm. In addition to the continuum there are also weak emission lines below k = 495 nm (Fig. 14). The intensity of the radiation drops appreciably below k = 300 nm and the emission zone, which is stable for higher wavelengths, begins to move [43]. 

After a preliminary study by Mortenson and Leighton S the thorough study by Edwards, Day and Overman s is notable. They analysed solutions of spblCHj) in benzene, octane and CCI4 for non-volatile forms of °Bi. Similar analyses were made on gaseous Pb(CH3)4 at 10 mm pressure, both pure and diluted with He, Ne, At, Kr and Xe. In solution at concentrations over 5 mole percent, about 50% of the Bi remained in a volatile form on dilution to mole fraction 0.05, the retention fell to 18% and rose again to over 90% in very dilute solutions. The retention values in the gas phase were then practically a continuation of those in dilute solution—between 80% and 90% for the pure gas at 10 mm pressure. With helium as diluent, the retention reached its maximum of 97% and the values decreased slowly to about 90% with xenon. 

P 12] A falling film micro reactor was applied for generating thin liquid films [6]. A reaction plate with 32 micro channels of channel width, depth and length of 600 pm, 300 pm and 66 mm, respectively, was used. Reaction plates made of pure nickel and iron were employed. The micro device was equipped with a quartz window transparent for the wavelength desired. A 1000 W xenon lamp was located in front of the window. The spectrum provided ranges from 190 to 2500 nm the maximum intensity of the lamp is given at about 800 nm. 

Fluorescence Instrumentation and Measurements. Fluorescence spectra of the FS samples were obtained on a steady state spectrofluorometer of modular construction with a 1000 W xenon arc lamp and tandem quarter meter excitation monochromator and quarter meter analysis monochromator. The diffraction gratings In the excitation monochromators have blaze angles that allow maximum light transmission at a wavelength of 240 nm. Uncorrected spectra were taken under front-face Illumination with exciting light at 260 nm. Monomer fluorescence was measured at 280 nm and exclmer fluorescence was measured at 330 nm, where there Is no overlap of exclmer and monomer bands. 

Fluorescence spectra of the novolac samples were measured on a Spex Fluorolog 212 spectrofluorometer with a 450 W xenon arc lamp and a Spex DM1B data station. Spectra were taken with front-face Illumination using a 343 or 348 nm excitation wavelength for solutions or films, respectively, which are near the maximum transmission region of this spectrometer. Spectra were corrected using a rhodamlne B reference. Monomer fluorescence was measured at 374 or 378 nm and exclmer fluorescence was measured at 470 nm. Monomer and exclmer peak heights were used In calculations of Ie/Im. The 1 monomer peak of pyrene was used to reduce overlap with the exclmer emission. 

Fig. 3.21 Maximum efficiency possible depending upon semiconductor bandgap, under xenon arc lamp and AM 1.5 solar illuminations.

In research laboratories, different types of light sources are used instead of solar radiation. In most cases the simulated spectrums have considerable deviation from the solar spectrum. Based on equation (3.6.9) Murphy et al [109] analyzed the maximum possible efficiencies for different materials according to their band gap in the case of solar global AM 1.5 illumination and xenon arc lamp, see Fig. 3.21. For example, anatase titania with a bandgap of 3.2 eV has a maximum possible efficiency of 1.3% under AM 1.5 illumination, and 1.7% using Xe lamp without any filter. For rutile titania these values are 2.2% and 2.3% respectively. 

As mentioned in sections 1.2.2.2 and 1.2.3.2, the photochromic reactions of spirobenzopyran and spironaphthoxazines show a marked solvent dependency and this is also the case with benzo and naphthopyrans. Consequently, spectral data collected from the literature is only comparable within any one study or where the same solvent has been used. This accounts for any discrepancies between one set of results and any other one listed in this and related sections of this chapter. The data normally quoted when discussing the properties of photochromic materials relate to the absorption maximum (2. ) of the coloured state, the change in optical density (absorbance) on exposure to the xenon light source (AOD) and the fade rate which is the time in seconds for the AOD to return to half of its equilibrium value. 

If a tube filled with Xenon is used instead of the spark in air the explosion begins 3.7 jusec after the first appearance of light. This value of 3.7 /usee means that ignition takes place ca 0.5 jusec after the flash has reached its maximum intensity. Again it is clear that only a small part of the incident light is used for igniting the nitrogen iodide... 

Xenon is an odourless, colourless, non-explosive gas present in the atmospheres of both Earth and Mars in concentrations of approximately 0.08 ppm. Its density is approximately three times and its viscosity twice that of nitrous oxide. Like other noble gases, such as helium and argon, its outer electron shell contains the maximum number of electrons (8) making the molecule highly stable chemically. Despite this, its anaesthetic activity indicates that xenon binds to cell proteins and cell membrane constituents. 

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