Ultraviolet transmission spectra

Ultraviolet transmission spectra of irradiated films showed absorbance changes similar in sensitivity to those of yc. The spectrum itself only showed a general absorbance increase in the 220-400 m/x region, with a slight indication of band formation near 315 m/x. Plots of absorbance increases against exposure time were linear for 285 m/x (ketonic carbonyl formation) and 315 m/x, with the absorbance increase amounting to 0.32 and 0.25, respectively, for 20/x films exposed 300 min. 

An empirical relationship has been shown between the contact angles for wettability of a polymer film and the degree to which photooxidation products have accumulated in the surface layers of the film. Changes in wettability of polymer films during photooxidation are markedly dependent on the nature of the polymer. In the detection and identification of the earliest processes and products of surface photooxidation, the wettability method is far more sensitive than the infrared transmission or attenuated reflectance spectra and is about as sensitive but more specific than the ultraviolet transmission spectrum. Contact angle measurements themselves can be used as leads in the selection of solvents for the separation and identification of photooxidation products formed in the surface layers of a polymer film and are potentially useful in establishment of rates of specific processes. 

Lighting. An important application of clear fused quartz is as envelop material for mercury vapor lamps (228). In addition to resistance to deformation at operating temperatures and pressures, fused quartz offers ultraviolet transmission to permit color correction. Color is corrected by coating the inside of the outer envelope of the mercury vapor lamp with phosphor (see LUMINESCENT MATERIALS). Ultraviolet light from the arc passes through the fused quartz envelope and excites the phosphor, producing a color nearer the red end of the spectrum (229). A more recent improvement is the incorporation of metal halides in the lamp (230,231). 

Figure 5.1 Ultraviolet absorption and visible fluorescence spectrograms of Uvitex OB. (a) Ultraviolet absorption spectrum(240-400 nm) of Uvitex OB (53 ppm) in 50% of ethyl alcohohdistilled water extractant (1 cm cell) showing absorption maximum at 378 nm using tungsten lamp (slit width 0.04 mm), (b) Visible fluorescence spectrogram (380-500 nm) of Uvitex OB (28 ppm) in 50% ethyl alcohohdistilled water extractant (1 cm cell) showing maxima at 415 and 435 nm using light filter with transmission 380-540 nm and high pressure mercury vapour lamp (slit width 0.1 mm). (Reproduced from Author s own files)...

An important test of a transient spectrometer s accuracy, stability, and noise level is provided by a baseline spectrum. This is an averaged spectrum obtained in exactly the same way as actual data, except that the ultraviolet excitation beam is kept blocked when it would otherwise be open. The lowest trace shown in Figure 2 is a typical 5-cycle baseline spectrum for our system. Systematic deviation from zero is less than 0. 01 absorbance units throughout, and the r. m. s. noise level varies from 0. 03 near the edges to 0. 007 near the center of the spectrum. These noise variations are inversely related to the detected single beam intensity spectrum, which drops on the blue side because of the continuum distribution and the transmissive properties of our beam combiner, and on the red side because of the photocathode response of the SIT detector head. A high degree of intensity linearity in the OMA is necessary for our... 

Figure 8 Solid lines) Spectral outputs for International Conference on Harmonization (ICH) visible and ultraviolet lamps with Hg emission lines removed dotted line) absorption spectrum for the iron-citrate complex dashed line) transmission profile for the yellow light filters used in this study and common to many manufacturing areas. Note the spectral overlap of both ICH lamps with iron-citrate complex absorption.

Using matched cuvettes for solvent and analyte is seldom practical for infrared measurements because it is difficult to obtain cells with identical transmission characteristics. Part of this difficulty results from degradation of the transparency of infrared cell windows (typically polished sodium chloride) with use due to attack by traces of moisture in the atmosphere and in samples. In addition, pathlengths are hard to reproduce because infrared cells are often less than 1 mm thick. Such narrow cells are required to permit the transmission of measurable intensities of infrared radiation through pure samples or through very concentrated solutions of the analyte. Measurements on dilute analyte solutions, as is done in ultraviolet or visible spectroscopy, are usually difficult because there are few good solvents that transmit over appreciable regions of the infrared spectrum. 

The optical properties of ceramics are useful in the ultraviolet, visible, and infrared ranges of the electromagnetic spectrum, and one key quantity used to describe the optical property of a material is the refractive index, which is a function of the frequency of the electromagnetic radiation. Other quantities used to characterize optical performance are absorption, transmission, and reflection these three properties sum to unity and are also frequency dependent. The last three properties govern many aspects of how light interacts with materials in windows, lenses, mirrors, and filters. In many consumer, decorative, and ornamental applications, the esthetic qualities of the ceramic, such as color, surface texture, gloss, opacity, and translucency, depend critically on how light interacts with the material. 

Compounds which absorb ultraviolet or visible light can be quantified for absorption measurements. Absorption measurements can be obtained in either the reflectance or transmission modes. The instrumentation required for these techniques is shown schematically in Figure 3.13. The vast majority of compounds absorb in the ultraviolet or visible region of the spectrum and deuterium and tungsten lamp sources can be used with prisms or gratings, cheaper instrumentation uses band-pass filters for monochromation. 

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