Energy transfer in CaSiO3 phosphors doped with Ce3+ and Tb3+

Calcium metasilicate phosphors activated by Ce³⁺ and Tb³⁺ have been studied for their emission characteristics. In two series of phosphors, one activator was kept at its optimum value while the other was varied. In another two series, one activator was kept below its optimum value and the other was varied. Concentration quenching effects start when each activator gives its maximum emission. There is clear evidence of an energy transfer from Ce³⁺ to Tb³⁺ because the⁵ D ₃ lines appear on addition of Ce³⁺ while they were conspicuously absent when Tb³⁺ alone was present. Their absence in singly activated phosphors could not have been due to cross-relaxation. Obviously X-ray excitation does not lead to⁵ D ₃ transitions which are achieved only by energy transfer. Further, considering the features of the emission spectra and the concentrations of activators used, the transfer could only be of the dipole-dipole type.     

KTB iron mineralogy at iridium deficient layers revealed by Mössbauer spectroscopy

Mössbauer spectroscopic studies of two sedimentary layers from Petriccio section in Gubbio formation are presented. It is found that these layers have almost the same iron phases nanophase hematite and phyllosilicate and with the same compositions as those in the Cretaceous-Tertiary Boundary (KTB) in Petriccio. The two layers also show enhancement in the siderophile elements such as Cr, Ni, Fe, Ca etc. to that found in the KTB layer. The two layers are well separated from the KTB layer, 128 and 149 cm below this layer, and show no enhancement of iridium. From the data it is suggested that the two layers also represent some kind of impact by extraterrestrial (ET) bolides.     

Uhf to Ka band upconverter

A balanced upconverter circuit has been developed in planar transmission line configuration using NEC GaAs beam lead Schottky barrier diodes. RF power output of +1.6 dBm SSB is obtained at Ka-band when up converter is driven by +17 dBm IF and +20 dBm LO signal.     

Electron diffraction data as a constraint in the determination of force field of thallous halide dimers

Electron diffraction data have been used as a constraint in the determination of force field for Tl₂F₂ having planar rhombic structure. The L-F approximation method, recently given by us, has also been applied to evaluate force constants for thallous halide dimers,e.g. T1₂F₂ and T1₂Cl₂. The results have been compared with the available experimental data in order to check the validity of the present work. It is concluded that non-bond experimental mean amplitudeU ₁..._Tl for Tl₂F₂ is capable of fixing the force field and L-F approximation gives reasonably good force fields for the two thallous halide dimers now under study.     

The spectrum of iodine excited in the presence of argon

The band systems of iodine in the regions 3455-3015 Å, 2785-2750 Å and 2730-2520 Å obtained by earlier workers using prism spectrographs are now photographed in the first and second orders of a 21-ft. grating spectrograph. A large number of new bands are obtained in all these three systems which are now extended to the regions 3461-3015 Å, 2785-2731 Å and 2729-2486 Å. The wavelengths and wavenumbers of all the bands are recorded along with their visually estimated intensities. The Deslandres schemes for the three systems representing all the bands are given and are found to be supported by the corresponding intensity distributions of the expected type. It was found that the two systems 3460-3015 Å and 2785-2731 Å do not involve for their lower levels the ground state as assumed by the earlier workers but the³Π_u (O _u ⁺) state at 15642 cm.^?1, which is also the lower state for the 4420-4000 Å system. The band system in the region 2730-2486 Å has for its lower level the ground state of the molecule as reported by the earlier workers. A reanalysis of this system made to include all the bands observed in the present experiments, gave vibrational constants slightly different from those obtained by earlier workers. The vibrational constants of the upper states of the four different systems that one gets by exciting iodine in the presence of argon are

System	Te	ωe	ωeXe	ωeYe
4400-4000Å	41411 cm.-1	102·2 cm.-1	0·34 cm.-1	..
3460-3015Å	45937 cm.-1	103·7 cm.-1	0·95 cm.-1	..
2785-2731Å	51847 cm.-1	112·4 cm.-1	0·711 cm.-1	0·004 cm.-1
2730-2486Å	47207 cm.-1	96·5 cm.-1	0·510 cm.-1	0·0033 cm.-1

     

Microestimation of explosives present in different compositions

Summary High explosives having the sameR _f values on a thin-layer chromatogram and difficult to separate are readily resolved as their coloured -complexes with aromatic amines. After liberation from their complexes on the plate, up to 1.5 g of the explosives can be conveniently estimated at their characteristic absorption maxima.

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Zusammenfassung Hochexplosive Substanzen mit gleichenR _f -Werten auf Dünnschichtchromatogrammen, die sich schlecht trennen lassen, werden als gefärbte -Komplexe mit aromatischen Aminen gut voneinander getrennt. Nach Freisetzung aus den Komplexen auf der Platte können bis zu 1,5 g der Explosivstoffe bei ihrem charakteristischen Absorptionsmaximum auf übliche Weise bestimmt werden.