Photolysis, apparatus for

Photolysis, apparatus for, 55, 17 Phthalimide, N-amino- [ 1//-Isoindole-1,3-(2//)-dione, 2-amino-, 55, 115 Potassium rew-butoxide [2-Propanol, 2-methyl-, potassium salt], 55,12, 13 Potassium iodide, 55, 71 Potassium permanganate [Permanganic acid, potassium salt], 55,68 Propane, 2,2 dimethyl 1 phenyl, 55, 112 Propane, 2 isocyano-2-methyl-, 55, 96... 

Photochemical ring contraction of 2-ethoxypyrrolin-5-ones, 59, 132 Photocycloaddition reactions, 57, 116 Photolysis, apparatus for, 55, 17 59, 132, 195... 

Photolysis, apparatus for, 47, 65 of butadiene to cis- and Irans-1,2-divinylcyclobutane, 47, 65 of dispiro[5.1.5.l]tetradecane-7,14-dione to cyclohexylidenecyclo-hexane, 47, 34... 

Phosphorous dichloride, phenyl-, 55, 128 Phosphorous oxy trichloride, 57, 103 Phosphorous pentachloride, 57, 63 58, 68 Phosphorus oxychloride, 56,4 Phosphorus triamide, hexaethyl-, 58, 143 Photocycloaddition reactions, 57,116 Photolysis, apparatus for, 55,17 Phth-Gly.Gly-OEt, 56, 93... 

Fig. 3. Schematic of apparatuses for flash photolysis, (a) A simple instmment, and (b) a more sophisticated one utilising longitudinal excitation.

Schematic diagram of a flash photolysis apparatus arranged for right-angle excitation and detection.

For the investigation of triplet state properties a laser flash photolysis apparatus was used. The excitation source was a Lambda Physik 1 M 50A nitrogen laser which furnished pulses of 3.5 ns half-width and 2 mJ energy. The fluorescence decay times were measured with the phase fluorimeter developed by Hauser et al. (11). 

The biscarbamate 5a and carbamate 3a were dissolved in acetonitrile (Fischer - ACS grade) and photolyzed with a 200-Watt medium pressure, Hanovla lamp in a typical preparative photolysis apparatus with pyrex sleeve. Integrated proton NMR data for the resultant solutions were made on a Jeol 4H-100 NMR. 

Both Porter s original flash photolysis apparatus and Pimentel s rapid scan spectrometer recorded the whole spectral region in a time which was short compared to the decay of the transient species. Kinetic information was obtained by repeatedly firing the photolytic flash lamp and making each spectroscopic measurement at a different time delay after each flash. The decay rate could then be extracted from this series of delayed spectra. Such a process clearly has limitations, particularly for IR measurements, where the decay must be slow compared to the scan rate of the spectrum. 

Fig. 3. Schematic diagram of the Northwestern apparatus for IR laser kinetic measurements in the gas phase. D, and D2 are InSb detectors with D2 being a high speed photovoltaic detector. M = Mirror, I = iris, C = chopper, BS = beam splitter, P = photolysis cell. [Reproduced with permission from Ouderkirk et al. (75).]...

The conventional photolysis apparatus consists of a concentrically arranged immersion well for the lamp, which is surrounded by a cooling jacket, which is itself surrounded by the reaction vessel. If this last compartment is used for the filter solution an additional external flask for the reaction mixture has to be used. There are also photochemical reactors wherein the lamps are arranged externally around the reaction flask. 

A thin-walled glass tube containing acetaldehyde (0.5 mL) and (f-BuO)2 (3 pL) was degassed by two freeze -thaw cycles and frozen in liquid N2. To this was vacuum transferred [1.1. IJpropellane (6-7 mg). The tube was sealed under vacuum, warmed to rt, and photolyzed for 15 min in a Rayonet style photolysis apparatus. The tube was broken open and the excess acetaldehyde allowed to evaporate at rt, leaving solid material. The solid was chromatographed (silica gel, pentane/Et20 5 1) to give the product, yield 8.4 mg (52%). 

One important difference in the design of a is conventional flash photolysis apparatus and the ns laser flash photolysis system is the size of the sample. The energy of laser pulses is usually very much lower than that of photographic flashes, typically 0.1 J as against 103 J. For this reason the laser light must be focussed on very small samples (0.1 ml for example). 

A flow apparatus for detroying 98% of the w-dissolved RDX at flow rates of 2500fi/min is described in Ref 114. The photolysis products include nitrogen gas, nitrous oxide gas. nitrate and nitrite ions, formaldehyde and ammonia. One intermediate product has been identified as l-nitroso-3,5-dimtro-l,3,5-triazacyclohexane. The primary photochemical steps involved in the photolysis are postulated... 

Janata E (1992b) Instrumentation of kinetic spectroscopy. 10. A modular data acquisition system for laser flash photolysis and pulse radiolysis experiments. Radiat Phys Chem 40 437-443 Janata E, Lilie J, Martin M (1993) Instrumentation of kinetic spectroscopy. 11. An apparatus for AC-conductivity measurements in laser flash photolysis and pulse radiolysis experiments. Radiat Phys Chem 43 353-356... 

Flash photolysis is a powerful technique for investigating the kinetics of conversion of the various forms of flavylium ions. 47cI Even with a simple flash-photolysis apparatus, with a time resolution of approximately 0.2 s, it is possible to obtain kinetic data that can complement and/or replace those obtainable by the pH-jump technique. 

The high value for the quenching of 3,4-dimethoxyacetophenone by phenol suggests that it is probable that within the lignin structure hydroxyl groups are able to quench carbonyls by a static mechanism to yield phenoxy-ketyl radical pairs which decay on a timescales faster than the time resolution of our laser flash photolysis apparatus. Intersystem crossing rate constants for triplet radical pairs in the restricted environments of micelles have been demonstrated to be of the order of 2 -5 x 106 s-1 (25, 24). However, in the lignin matrix where diffusional processes are likely to be... 

A diagram of the photolysis apparatus used by the checker for all syntheses listed is shown in Fig. 22. 

The absorption spectra of the dyes were measured with a Shimadzu UV-3101 PC spectrophotometer (Japan) in a cell with a 1-cm optical path length. The fluorescence and fluorescence excitation spectra were studied with the use of a Shimadzu RF-5301 PC spectrofluorimeter. To study the triplet state of the dyes, apparatuses of flash photolysis with xenon lamp excitation (with an energy of 50 J and a pulse length at half maximum of xi/2 = 7 ps) [6] was used. To detect the triplet state of the dyes, the solutions were deoxygenated using a vacuum unit or purged with argon for experiments on the laser flash photolysis apparatus. A... 

---