Short-wave Ultraviolet Radiation Research Articles

Studies on Aminoanthraquinone Compounds IV–Photochemistry of some Simple Derivatives in Solution and on Polymer Films

An attempt has been made to determine the validity of the concept of the dye–ethanolsystem as a model for the photochemical degradation of textile materials sensitised by anthraquinone vat dyes. The action of (a) near–ultraviolet and visible radiation and (b) short–wave ultraviolet radiation (mainly 253–7 mμ) on anaerobic solutions of 1–aminoanthraquinone in ethanol, n–hexane, ethyl acetate, and carbon tetrachloride has been studied. Extensive fading of the dye occurs in these solvents with both typesof radiation. In the hydrogen–containing solvents characteristic spectra of reduction products of 1–aminoanthraquinone are produced, whereas in carbon tetrachloride there is extensive general destruction of the absorbing systems. The spectral changes occurring on the irradiation under anaerobic conditions of 1, 5–diaminoanthraquinone and 2–aminoanthraquinone in solution in ethanol and dyedon polymer films of N–methoxymethyl nylon, nylon 6. 6, and secondary cellulose acetate are compared. Only with 1, 5–diaminoanthraquinone and 1–aminoanthraquinone on N–methoxymethylnylon film are the changes on irradiation in dry nitrogen similar to those in ethanol. It is concluded that the photochemical behaviour ofanthraquinone dyes in organic solvents and in polymer systems can show considerable differences.

An open cathodoluminescent shortwave ultraviolet radiation receiver

An open cathodoluminescent shortwave ultraviolet radiation receiver

Atmospheric Ozone in Helsinki and Its Effects on Rubber

Abstract Although the amount of ozone in the atmosphere is rather small compared with other gases its importance in several respects is rather great. This is mainly due to the high absorption and reacting capacities of ozone. The absorption capacity becomes apparent among other ways in the fact that the ozone layer of the atmosphere absorbs the excessive ultraviolet radiation coming from space as well as heat radiation from the earth. On the other hand, the reacting capacity can best be observed in numerous harmful oxidation phenomena, among which a typical example is the cracking of the surface of rubber products, caused by ozone. Generation and distribution of ozone in the atmosphere.—It is assumed that ozone is generated in the upper atmosphere photochemically under the influence of ultraviolet radiation. The shortwave ultraviolet radiation of a wavelength of about 2000 A breaks the oxygen molecules into atoms that combine with other oxygen molecules to form ozone. The ozone in turn absorbs ultraviolet radiation of a longer wavelength, which again breaks up the ozone thus maintaining an equilibrium in the concentration. This equilibrium is largely dependent upon temperature, the lower temperatures giving rise to a considerably higher concentration of ozone than the higher temperatures. The maximum concentration of ozone in the atmosphere is at an altitude of about 20 kilometers from the earth. The distance of this maximum from the surface of the earth, however, varies over different parts of the globe and according to the season. There is a constant movement of ozone from the actual ozone layer to the lower air regions near the surface of the earth. The major part of the ozone is destroyed near the earth's surface, as it comes into contact with oxidizable matter. Generally speaking, this movement of the ozone into the lower parts of the atmosphere is caused by turbulence, that is, by mixing of the air masses. In the atmosphere there is a regular circulation between the different regions. Near the equator the direction of the movement is upwards, from the troposphere to the stratosphere, while around the latitude 60 it is the other way around. This phenomenon explains, for example, the relatively large increase in radioactivity in polar districts and, in addition, it offers a partial explanation of the high ozone concentration near the surface of the earth in these parts compared with that in warmer regions.

Photochemistry of Cellulose in the Far Ultra-violet

IT is known that hydrogen, carbon monoxide and carbon dioxide are evolved, and aldehyde and carboxyl groups formed1, during the photolysis of cellulose with short-wave ultra-violet radiation in the absence of oxygen; but the complications produced by the presence of oxygen and water vapour are not fully understood. We have found that temperature markedly affects the nature of the results obtained in atmospheres of dry oxygen and dry nitrogen, and have obtained evidence which suggests that the type of reactions involved are different in oxygen-containing atmospheres in the presence and absence of water vapour. In our experiments we have exposed undyed bleached cotton yarn to the radiations from a low-pressure mercury-vapour lamp emitting mainly at 2537 A. The yarn was contained in the inner compartment of a brass cell fitted with a quartz window. The cell was maintained at a constant temperature by circulating a suitable heating (or cooling) medium through the outer compartment. During the experiment a stream of gas heated to the required temperature was passed through the cell. The degradation of the cotton was assessed by measurements of tensile strength, fluidity (poise−1) in cuprammonium2, reducing power3, and carboxyl content4. Various attempts5 have been made to convert fluidity into degree of polymerization but the accuracy of these relations is doubtful where the cellulose has been subjected to breakdown of largely unknown character. Accordingly, the rise in fluidity of the cotton produced by irradiation has been used as a quantitative measure of the extent of chemical action. A large rise in fluidity corresponds to considerable breakdown of the cellulose molecule.

Studies of Color Centers Produced in Apatite Halophosphates by Shortwave Ultraviolet Radiation

An investigation has been made of the effects of shortwave ultraviolet radiation on nonluminescent base materials in which it is possible to isolate other electronic processes from those of luminescence. This radiation has been found to produce color centers in a typical commercial halophosphate base material, in a similar preparation with manganese present in addition, and also in compounds and solid solutions in the systems , , and . All colors may be bleached thermally and some optically as well. In preparations containing strontium, thermal bleaching is accompanied by luminescence, and glow curves have been measured. Optical bleaching is also accompanied by luminescence.

New find of scheelite at Sekihata in Yamahashi Village, Fukushima Prefecture

A new occurrence of scheelite from Yamahashi Village, Fukushima Prefecture is described. The mineral occurs in skarn minerals, such as garnet and epidote, which were intruded by quartz veins. It shows a pale blue fluorescence in short wave ultraviolet radiation and its crystals have a common habit with well develope {101} and {111} forms. The specific gravity determined by a pycnometer was G=6.076 The refractive indices determined by a method of minimum deviation were ω=1.9212, ε=1.9282, ε-ω=(-) 0.0070. The chemical analysis shows a result shown in Table 2, No. 1.

Towery manganocalcite from Hosokura mine, Miyagi Prefecture

Manganocalcite was occurred, as towery parallel aggregate shown in Fig. 1 and 3 at Hosokura mine, Miyagi Prefecture. The colour is pale pink and the mineral shows red fluorescence in short wave ultraviolet radiation. The measured specific gravity is G=2.798 at 4°C and the index of refraction is ω=1.6785, e=1.5004, e-ω-(-)0.1781. The analysis shows the percentages and the mineral proportions as shown in Table 1, No. 1.

Decay and quenching of fluorescence in willemite

With the aid of measurements of the efficiency and the decay of the fluorescence of willemite, it is shown that fluorescence excited by short-wave ultra violet radiation is quenched by two kinds of radiation-less processes. One starts from the high excited state reached in the excitation process; its rate is governed by a first order process which, competing with the second order process leading to fluorescence, causes the efficiency of fluorescence to be dependent on the exciting intensity. This process is increased by iron and also by ball-milling. The second radiation-less process starts from an excited state of the manganese centre. It runs parallel to the slow fluorescence transition and thus influences the decay of the fluorescence. It increases strongly with temperature; the variation can be satisfactorily described with the aid of an activation energy. For excitation by long-wave ultra violet only the latter process plays a part.

Fluorescence of Tungstates and Molybdates

THE tungstates of calcium, strontium, magnesium and zinc, and the molybdates of calcium are known to show luminescence upon excitation by cathode rays or short-wave ultra-violet radiation. It is commonly assumed that this luminescence is characteristic of the tungstate and molybdate groups. If this is true, there must be a reason why other tungstates and molybdates are found to be non-luminescent. Studying a number of different tungstates and molybdates in this Laboratory, we have found this reason to be the temperature-quenching.

Electric Discharge Lamps for Photography

MR. H. K. BOURNE presented a paper on this subject, illustrated by a comprehensive display of typical lamps, at a meeting of the Association for Scientific Photography on January 27. Photographically, electric discharge lamps have high actinic efficiency combined with low heating power; and they have a long life. Since the early days of the Cooper-Hewitt lamp, a glass tube several feet in length with a mercury pool at the end, development has proceeded along two divergent lines, low pressure and high pressure. In the modern low-pressure lamp, the pressure of mercury vapour is only a fraction of a millimetre; it emits considerable long- and short-wave ultra-violet radiation, which by means of fluorescent powders on the inside of the tube is converted to visible light of longer wave-lengths. It provides a well-diffused light-source closely resembling daylight and capable of giving accurate colour rendering. The high-pressure mercury vapour lamp consists of an inner glass tube containing the arc, sealed into an outer glass jacket. The arc tube pressure is about 1 atmosphere, and the arc is constricted into a narrow cord along the axis of the tube. The outer envelope is filled with an inert atmosphere. There is a wide range of types, the most powerful being in powers of the order of 10 kW or higher, with a brightness ranging up to 100,000 candles per sq. cm. The spectrum is linear in character, and fluorescent powders cannot be used with the high brightness lamps; but with increasing pressure there is an improvement in the colour, the main lines broadening while the amount of continuous background increases. An amalgam of cadmium is sometimes used to improve colour. Brightness increases with increases of loading per unit length in the arc column, which has been made possible, first by the use of quartz tubes with molybdenum foil vacuum-tight seals, and later by the introduction of water-cooling, which dissipates approximately 70 per cent of the radiated heat. The author described a number of lamps including a compact source lamp with a maximum brightness of 18,000 c./sq. cm., a self-contained metal box-lamp which can be used without a lamphouse for the illumination of laboratory instruments, a 100-hour-life water-cooled high-pressure lamp with a luminous efficiency of 65 lumens per watt, a peak brightness of 30,000 c./sq. cm. and an internal pressure of about 75 atmospheres, and the B.T.H. syroposcopic tube which can give recurring flashes at a predetermined frequency or be employed as a synchronized flash-lamp for ordinary photography.