High pressure lamps

In contrast to the low-pressure lamps (1—130 Pa) which primarily emit at the resonance line at A = 254nm, high-pressure lamps (lO —10 Pa) also produce numerous bands in the UV and VIS regions (Fig. 16). Table 3 lists the emission lines and the relative spectral energies of the most important mercury lamps (see also [44]). The addition of cadmium to a mercury vapor lamp increases the numbei of emission lines particularly in the visible region of the spectrum [45] so that it i. also possible to work at A = 326, 468, 480, 509 and 644 nm [46]. 

Detection and result The chromatogram was dried in a stream of warm air for 10 min, immersed in the reagent solution for 3 s and then subjected to intense UV radiation (high pressure lamp, A = 365 nm) for up to 10 min. Terephthalic (hRf 0 - 5), pimelic (hRf 55), suberic (hRf 60), sebacic (hRf 65 — 70) and benzoic acids (hRf 70 — 75) together with sorbic, malic, adipic, citric, tartaric, lactic and fumaric acids only exhibited a reaction on silica gel layers at higher concentrations. 4-Hydroxybenzoic, salicylic and acetylsalicylic acids fluoresced light blue after irradiation. The detection limit per chromatogram zone was 0.5 pg for salicylic acid and more than 5 pg for benzoic acid. 

Preparation of 18,20-Cyclo-5a-pregnane-3, 20-diol 3-Acetate ° A solution of 5 g of 3j9-hydroxy-5oc-pregnan-20-one 3-acetate in 1000 ml of spectroscopically pure ethanol is irradiated with a 250 Watt Philips Biosol A mercury high pressure lamp No. 10/27 through a cental water cooled pyrex jacket under nitrogen for 4 hr. The solvent is then evaporated under reduced pressure and the residues from 2 such reactions are combined and chromatographed on 300 g of neutral alumina (activity II). 

High Pressure Lamp.—A lamp filled with mercury or xenon vapor (or a mixture of them) operated at about 10 or more atmospheres pressure. Although the total output is very high, the emission is largely above 3000 A. In mercury or mercury-xenon lamps it consists of broad lines superimposed on a strong continuum. The 2537 A. line is almost entirely lost by self-absorption in the lamp. 

Medium Pressure Lamp.—A lamp filled with mercury vapor and operated at a pressure of about 1 atmosphere. The total intensity in the near ultraviolet and visible is lower than that of high pressure lamps, but photochemically useful light at wavelengths less than 3000 A. is produced. The ultraviolet spectrum consists of reasonably narrow lines with only a weak continuum. Hence, in conjunction with a filter or monochromator it is a good source for monochromatic radiation including reversed 2537-A. radiation (see definition below). 

Consider now photochemical properties of (=Si-0)3Si-0-0 radicals [56,66,68]. Under the UV irradiation (unfiltered light of a mercury high pressure lamp equipped by a water filter, T — 300 K) the following processes were observed (1) the decrease in the intensity of the EPR signal from peroxy radicals (2) the formation of (=Si-0)3Si-0 radicals whose number... 

Compounds 63 and 64 coexist as a 1 1 equilibrium mixture upon irradiation of one or the other in C6D6 (mercury high-pressure lamp Phillips, HPK 125W, Duran-50 filter). On heating of each of the two isomers separately at 150 °C, compound 65 (yield 100% or 48%, respectively) is formed by a skeletal rearrangement. Finally, compound 67 can undergo complete photochemical isomerization to furnish an isomeric mixture of two compounds 65 and 66 (ratio 80 20) (Scheme 6) <1997AGE1337>. 

The native fluorescence spectrum of dipyridamole was recorded in ethanol (5 pg/mL) using a Kontron spectrofluorimeter, Model SFM 25 A, equipped with a 150 W xenon-high pressure lamp and driven by a PC Pentium-II computer. As shown in Figure 5, the excitation maximum was found at 297 nm, and the emission maximum was located at 467 nm. 

For bulk heteroj unction solar cells made from MDMO-PPV/PCBM, measured under metal halogenide lamps, a mismatch factor of M 0.76 has been determined, while for xenon high-pressure lamps, M rs 0.9 is used. 

An elegant epimerization of 4 -phenylseleno deoxyribonucleosides 145 was achieved by irradiation of the selenoacetal in the presence of diphenyl di-selenide with a Hg-high pressure lamp [Eq. (47)] [113]. This epimerization proceeds via the reversible formation of the 4 -C radical 146. After 2 h of irradiation, the equilibrium mixture 145/147 = 29 71 is reached. 

Spectrofluorimeter, Kontron SFM 25 equipped with a 150-W xenon high-pressure lamp was used for recording the fluorescence spectrum of gemifloxacin mesylate in water. As shown in Fig. 4.2, the fluorescence spectrum exhibited two excitation maxima at 266 and 342 nm and one emission maximum at 391 nm. The fluorescence intensity obtained at l x 266 nm was found to be more (5-25% depending on the solvent used) than that obtained at 342 nm. Moreover, the position of the emission maximum was red shifted in 0.1 N HCl solution (405 nm) and blue shifted in 0.1 N NaOH solution (390 nm). 

Bis[trifluoromethyl] Ditellurium An apparatus for irradiation consisting of a reaction vessel, a low-temperature (— 25°) cooler with argon adapter, and an external mercury high-pressure lamp (Heraeus, TQ 150) is assembled. Under an atmosphere of argon 2.65 g (10 mmol) bis[trifluoromethyl] tellurium, 13.6 g (200 mmol) furan, and several glass rings are plaeed into the reaction vessel. The mixture is irradiated for 54 h and stirred to remove the tellurium mirror from the walls of the reaction vessel. The solvent is distilled at atmospheric pressure until the bath temperature reaches 80°. The residue is distilled at 0.001 torr by increasing the temperature slowly from — 78° to + 25° yield 43% b.p. 120°/760 torr. 

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