Mizuki Yoshida

Photoionization of Indole in Alkaline Aqueous Solutions at 77°K

The photoionization process of indole in alkaline aqueous solutions at 77°K and the recombination process of trapped electron with its mother molecule were investigated. The fluorescence spectrum of indole in these glassy media depended on the NaOH concentration; the disappearance of the 325 nm band at the NaOH concentrations higher than 5 M with the appearance of a fluorescence band at 375 nm. The latter emission is possibly ascribed to the fluorescence of indole anion formed by proton dissociation in the excited singlet state of indole. The intensities of the 375 nm band and the ESR signal due to trapped electrons were dependent on the NaOH concentration and increased steeply with increasing the NaOH concentration. There was a parallel relation between the indole anion concentration and the trapped electron density to some extent. The dependence of the ESR signal intensity on irradiation intensity suggested that the photoionization of indole in alkaline aqueous solution occurred through a two photon process. The presence of a photoactive intermediate for absorbing the second photon was further investigated with simultaneous irradiation of two different wavelength lights. The trapped electron was detrapped with the irradiation of visible light (e.g. 580 nm), and its recombination with mother molecule caused an emission with the same spectrum as indole phosphorescence. The molecular species of the photoactive intermediate in alkaline aqueous solutions seems to be the indole anion. The photoionization in NaOH aqueous solution at 77°K was also compared with that in methanolic glassy solution.

Mechanism of E.M.F. Production in Sodium Sensitive Glass Electrode

The e.m.f. (electromotive force) change of sodium sensitive glass electrode was measured in the buffered solution in the process of neutralization with sodium hydroxide. Just above the neutral point where the sodium ion concentration was kept constant, a sudden change of e.m.f. was observed. This phenomenon was explained with respect to the phase boundary ion exchange hypothesis. The data obtained were compared with Nicolskys simple and generalized theories which succussfully explained e.m.f. changes of various glass electrodes. But, Nicolskys equations failed in giving an appropriate value of the slope in the plot of e.m.f. versus log CNa.

Method for Measuring Rate of Movement of Sand Using Laser Beam

A new method for measuring the rate of movement of sand using an He–Ne laser beam has been developed. This method enables us to measure the velocity of blown sand in the field. The apparatus is composed of an He–Ne laser, a photo-detection system (slit width; 0.3–3.0 mm), a 5-channel pulse width analyzer and a multi-purpose counter. When a sand grain passes across the laser beam, a shadow is thrown upon the light-sensitive surface of the photodetector. The change in photocurrent, after amplification and pulse shaping, is fed to the pulse width analyzer. The pulse width includes information on both the velocity and size of the blown sand grains. Using a nearly uniform size of sand grains, the velocity distribution of blown sand can be measured.