Sample tube during irradiation

The QDNP experiments carried out on the thermal reactions 1,3,4 and 5 simply involved heating the reactants within the probes of NMR spectrometers or rapid mixing of reactants before insertion of the sample tubes. During the studies of photochemical reactions, simple modifications of spectrometer probes were introduced to permit irradiation of the reactants within the probes. These simple modifications have been described for 60 Mc/sec ) and for 100 Mc/sec-... 

The sample tubes were Irradiated for the specified total doses In a Gammacell-200 (Atomic Energy of Canada Ltd.) Co source. Allowing for °Co decay, the standard dose rate calibrated Iqr Frlcke dosimetry decreased from 0.094 Mrad hr (August, 1982) to 0.078 Mrad hr (January, 1984) during the period of this Investigation. 

For irradiation at 313 m/, the reactor consisted of a 6- X 2-inch o.d. cylindrical borosilicate glass tube fitted directly to the mass spectrometer by a 24/40 joint. A Hanovia analytical lamp, having an estimated output of 325 watts, was mounted externally alongside the tube. The radiation received by the samples inside the tube was filtered through borosilicate glass and was essentially 313 m/. The ambient temperature within the reactor during irradiation was 25 °C. Some comparative experiments were carried out at 70 °C. with additional heating. There was no detectable temperature effect between 25° and 70°C., and the results reported here are for 25 °C. 

Irradiation procedures. Mesophase solutions and neat solid samples of BN were prepared and sealed under N2 or vacuum in Kimax capillary tubes. Isotropic samples were either degassed (freeze-pump-thaw techniques) and sealed in pyrex tubes or saturated with N2 in pyrex tubes. Nitrogen was bubbled through the latter solutions during irradiation periods. When ther-mostatted, samples were placed in a temperature controlled ( 1°) water bath. All samples were irradiated with a 450 W Hanovia medium pressure Hg arc and were stored at -30°C until their futher use. Usually, a "dark sample was prepared and treated in an identical fashion to the irradiated samples except that it was shielded from the light. JSN from each tube was recovered by either column chromatography (silica or alumina and pentane eluant) at 4°C followed by solvent removal at 0°C and reduced pressure or by hplc (tr-hexane) at room temperature followed by solvent removal at 0°C and reduced pressure. Neat solid samples were dissolved in one of either benzene, tetrahydrofuran or toluene and were frozen until analyzed. 

Time variations in the intensity of the flux during irradiation. This is an important consideration only when a single sample transfer system is used. Gas-filled BF3 neutron counter tubes are often used to monitor the neutron flux in order to normalize the data when the sample and the standard are not irradiated simultaneously. Gain shifts and dead-time effects associated with the use of neutron monitoring detectors also contribute to the errors associated with a single sample transfer system. 

To check for possible contamination that might have occurred during sampling, samples were collected in the clean room, directly from the sampling tube after filtration. Tests were made on Cd, Co, Cu, Ni and Zn determined by ETAAS after APDC/DDDC complexation (Cd, Cu) or DPASV after UV-irradiation (Cd, Co, Cu, Ni and Zn). 

Electrical Connections. Electrical measurements can be made on the samples during irradiation or subsequent annealing. To do this, an electrical connector (7) is attached to the sealing plug (8) and provides electrical connections between the inside and the outside of the irradiation enclosure without impeding the connection or disconnection of the tube (6). 

Pyrex nuclear magnetic resonance (NMR) sample tubes (0.4 mm -w all thickness) are suitable for containing the sample to be irradiated. These can be purchased from Kontes Glass Co. in several different grades. The tubes can be stoppered with rubber septa during experiments requiring anaerobic conditions. 

The distance between the lamp and the focusing lens was 15 cm. The filter was placed close to the focusing lens. Irradiation of the sample was carried out in a quartz tube (10 mm diameter) at a distance of 5 cm from the lens. Caution During irradiation high-quality safety goggles ( welder s goggles ) must be worn. 

For the UV studies, sample solutions (monomer/solvent, 20 ml) were prepared in pyrex tubes as before with the gamma irradiation system and the tubes positioned on a motor driven ventilated circulating drum at a distance of 30 cm unless otherwise stated from the UV source (90W, high presure, Hg type 93110E E, Philips) for 6-24 hours at 24 1 C. The polymer films were so positioned that, during irradiation, the surfaces of the films were perpendicular to the incident radiation. After irradiation, films were treated as for the gamma work. 

A solution of 7-bromo-2-(fV-methylanilino)hept-2-enenitrile (145 mg, 0.52 mmol) in cyclohexane (60 ml) was placed in a quartz tube and purged with oxygen. The sample was irradiated for 8h in a Rayonet Model RPR-100 Reactor using 254 nm light. An oxygen atmosphere was maintained during... 

Photoirradiation and ESR Measurements. The samples of cellulose and cellulose derivatives were packed uniformly into clear fused Suprasil quartz tubes (O.D. 4 mm), which did not produce any ESR signal during the irradiated sequences. The quartz tubes containing the samples were evacuated to a constant pressure (10 6 mm Hg) and sealed. The source of ultraviolet irradiation was a high pressure mercury-xenon compact arc lamp (Conrad Hanovia type 901 BOOH, 200 W) which... 

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