Variation Of Emission Spectra Research Articles

Variations in emission spectra from warm water fogs: Evidence for clusters in the vapor phase

The ability of water to form molecular aggregates or clusters by hydrogen bonding is believed to be responsible for its unexplained spectral emission and absorption in many wavelength regions including the infrared. Data from 442 spectroradiometer observations of steam clouds and warm water fogs in the 7–13 μm infrared atmospheric ‘window’ region are summarized, and evidence is presented for cluster activity in the vapor phase. Observations show agreement with theory relating infrared absorption and emission to intermolecular vibrations in distributions of water ion clusters with mean sizes of 10–13 molecules per cluster. Clusters are implicated not only in infrared ‘continuum’ absorption of water vapor in the atmosphere, but in ionic activity affecting seemingly diverse phenomena such as cloud nucleation and the electrical conductivity of moist air.

Some Optical Properties of Lead-Activated Sodium Chloride Phosphors

Absorption and luminescence phenomena in NaCl:Pb phosphors have been found to be rather complex. Melt-grown NaCl:Pb has an asymmetrical, 2730A-peaked absorption band. The variation of emission spectrum with wave-length of excitation within this band shows that it consists of two poorly resolved absorption bands, one peaking at 2730A and the other at 2900A. At low Pb concentrations, irradiation into the first of these causes a near-ultraviolet emission peaking at 3200A; irradiation into the second causes a visible emission peaking at about 4500A. At high Pb concentrations, irradiation into the first band gives a second near-ultraviolet emission band peaking at 3850A in addition to the one peaking at 3200A. Precipitated NaCl:Pb shows all the above phenomena, and in addition, has an excitation band peaking at 2600A, producing simultaneously a 3300A-peaked emission and a visible emission. The NaCl:Pb phosphors are unstable, deteriorating after a few days at room temperature and more rapidly at 130°. X-irradiation of these phosphors destroys the above absorption and emissions, and gives a print-out effect due apparently to the formation of colloidal Pb. The x-rayed material can be excited by near ultraviolet to give a red emission, peaking at about 6100A. Some suggestions concerning the interpretation of the above phenomena are given.

Variation of Emission Spectrum of Manganese-Activated Zinc Beryllium Silicate with Decay Time

Variation of Emission Spectrum of Manganese-Activated Zinc Beryllium Silicate with Decay Time