The aqualuminescence intensity and the emission spectra of -irradiated NaCl has been studied in pure water and water doped with monovalent and divalent cations. An enhancement of aqualuminescence is observed in the presence of these metal ions. The mechanism of luminescence in the presence of metal ions is explained on the basis of the rate constants of e
with the metal ions.
The lyoluminescence emission spectra of luminol, induced by -irradiated NaCl in aqueous alkaline earth metal hydroxides, are recorded. Continuous emission bands are observed in the visible region from 390 to 535 nm. These emission bands on resolution showed two peaks at 430 and 460 nm, respectively in all hydroxides. An additional band of 490 appears in the case of calcium hydroxide. The colour centres released during disintegration of irradiated NaCl crystals in aqueous solution react with luminol to produce various excited molecular species, which are responsible for observed lyoluminescence of luminol.
It is now well established that the oxidation of iodide ions and the reduction of nitrate ions take place when -irradiated sodium chloride is dissolved in aqueous iodide and nitrate solutions, respectively. The yield of iodine decreases and that of nitrite increases with increasing concentration of nitrate in a binary mixture of iodide and nitrate when the irradiated salt is dissolved in it. The results are explained on the basis of the reactions of colour centres with iodide and nitrate ions present in the binary mixture.
Reduction of nitrate to nitrite takes place when the stored energy in the form of colour centres is released during dissolution of -irradiated NaCl crystals in aqueous sodium nitrate solution. Various parameters like dose, amount, storage time and particle size of irradiated NaCl salt which control the yield of nitrite have been studied. Similarly, the effect of concentration of NaNO3 and the role of precipitation on the yields of nitrite in aqueous TlNO3 and AgNO3 have been investigated. The energy transfer parameter has been determined as the ratio of G/NO
/ obtained by the addition of irradiated NaCl to that of direct -radiolysis. The data permit the evaluation of the concentration of colour centres in the irradiated NaCl crystals on the basis of the mechanism of reduction of nitrate.
Solvoluminescence /SL/ of -irradiated LiCl crystals have been studied in some organic solvents. The SL emission spectra of LiCl crystals were recorded in N-methyl acetamide, nitrobenzene, cyclohexanol, cyclohexanone and pure water. The total SL intensity of LiCl in various organic solvents was found to vary with the type and nature of the solvent. The results are explained on the basis of the electron-scavenging effect and complexing abilities of the solvents.
It is well known that paramagnetic centers are formed when Na2SO4 crystals are exposed to -radiation. The dissolution of such crystals in aqueous ammonium nitrate results in reduction of nitrate to nitrite. Various factors which influence the yield of nitrite are investigated. The yield of nitrite is found to vary with the amount of irradiated Na2SO4 added, the dose absorbed by Na2SO4 crystals, the storing period of the irradiated salt, photoannealing time, concentration of aqueous ammonium nitrate and particle size of the Na2SO4 crystals. The G(NO
) value under optimum conditions of the conversion of nitrate to nitrite by irradiated Na2SO4 in aqueous ammonium nitrate is 0.009. The efficiency of energy transfer is 1.5%. The mechanism of reduction is based on the reactions of paramagnetic centers with nitrate ions.
Lyoluminescence of luminol induced by -irradiated NaCl has been studied in aqueous amines. The emission spectra of lyoluminescence are recorded on 400 ASA Kodak film using a Fuess spectrograph. A broad continuous emission band appears in the visible region from 390 to 500 nm. The emission band showed two peaks centered at 430 and 470 nm. The 430 nm peak is more intense in secondary amines while the 470 nm band is more intense in primary amines. The mechanism of light emission is based on the comparative study of lyoluminescence, fluorescence and chemiluminescence of luminol in aqueous amines.
The oxidation of iron/II/ ions has been studied by dissolving -irradiated NaCl crystals in aqueous Fricke solution. The yield of iron/III/ ions was determined as a function of the amount of NaCl added, storage time, dose, concentration of iron/II/ ions and pH of the Fricke solution. The energy transfer parameter, , which is the ratio of G/Fe3+/ obtained by the addition of irradiated NaCl to that by direct radiolysis was evaluated.
It is well known that ammonium halide (NH4X) crystals, on -exposure, store energy in the form of primary and secondary radiolytic products. Such crystals on dissolution in aqueous iodide and nitrate solutions result in oxidation of iodide and reduction of nitrate, respectively. The yields of iodine and nitrite are determined by chemical methods under varying conditions of the amount, dose and particle size of the irradiated ammonium halide salts. The maximum values of the efficiency of energy transfer for oxidation and reduction processes for ammonium halide salts correspond to 40% and 10%, respectively. At low doses, an empirical relation proposed between the percent efficiency of energy transfer and the absorbed dose is valid. The concentrations of inherent oxidizing and reducing species initially present are 7.0×1018 and 1.0×1018 per mol of ammonium halide, respectively.
Authors:C. Kalkar, M. Bhujbal, and Rajashree Barve
Radiolysis of aqueous sodium nitrate solution was studied as a function of concentration in the range 10–4M to 1M NaNO3. The radiolytic yield of nitrite was found to be linear with dose and concentration. The effect of transition metal chloride additives on the radiolysis of 0.01M NaNO3 resulted in higher and lower yields of nitrite in the presence of cobalt and nickel chlorides, respectively, than that obtained in the pure nitrate system. The reduction of nitrate to nitrite is totally quenched even at very low concentration of copper chloride in the binary mixture. The results are explained on the basis of oxidizing and reducing properties of transition metal ions.