Fluorescence, excitation, and pulsed fluorescence measurements have been made on a single crystal of CaWO4 over wide temperature range. The dependences the integrated intensities lifetimes were obtained for different excitation wavelengths. A sharp increase in is observed below about 75°K zero-phonon lines can be observed. These results are used to formulate model tungstate luminescent center based WO42− ion field S4 symmetry. Energy migration impurity trapping effects also discussed.

This paper examines the recent attempts to develop geographies of science both within, and beyond, discipline geography. Such efforts have been most successful in work by historical geographers historians Investigating `geographical turn' evident across studies more widely, this considers a broad range engagements with spatiality historians, sociologists, anthropologists posthumanist practice theorists. In doing so, thus argues that different are emerging. Indeed, bringing together...

A comparison of the spectroscopic parameters Raman-active vibronic modes in various crystalline materials with a view to use these crystals for stimulated Raman scattering (SRS) is presented. It includes data on frequency shift, linewidth, integral, and peak cross sections. For steady-state SRS highest gain coefficient has been proved be barium nitrate sodium crystals; transient it expected lithium niobate tungstate crystals. Barium strontium are proposed as new highly efficient both cases.

An intracavity solid-state Ba(NO3)2 Raman shifter produces 1.535–1.556-μm radiation when pumped by a Nd3+:YAG laser operating at 1.318–1.338 μm. beam cleanup and 48% energy conversion efficiency have been observed. Second Stokes lines 1.82–186 μm were observed in the output higher pump input levels. Diffraction-limited pulses of 0.25 J 1.535–1.56 achieved.

Details of the optical-spectroscopic properties alexandrite (${\mathrm{BeAl}}_{2}$${\mathrm{O}}_{4}$:${\mathrm{Cr}}^{3+}$) crystals were studied by different laser-spectroscopy techniques. The temperature dependences fluorescence lifetimes and widths zero-phonon lines found to be quite for ${\mathrm{Cr}}^{3+}$ ions in mirror inversion crystal-field sites. results indicate that direct phonon-absorption processes dominate both thermal line broadening lifetime quenching sites while...

Results of an extensive investigation the optical properties CaW${\mathrm{O}}_{4}$: ${\mathrm{Sm}}^{3+}$ are reported. Absorption, fluorescence, and excitation spectra pulsed fluorescence measurements were obtained at temperatures from below 8 K to room temperature on undoped single crystal crystals containing samarium concentrations ranging between 0.01% 1.0%. An empirical energy-level diagram is determined for trivalent in this host existance several different nonequivalent crystal-field...

The luminescence properties of several different undoped and Eu3+-doped LiNbO3 crystals powders have been investigated. Emission excitation spectra fluorescence lifetimes were measured at low temperatures the diffuse reflectance room temperature. results show that behavior is very sensitive to Li/Nb ratio. In stoichiometric samples emission originates from intrinsic niobate groups, whereas in with a ratio 48.6/50.0 only groups or near defect sites observed.

The usual model for singlet-exciton motion and trapping in molecular crystals is generalized to arbitrary finite regions about each activator more than nearest-neighbor steps by the random walker. properties of extended regions, which simulate activator-induced host traps, are obtained rigorously applying general results three-dimensional walks. capacity $C(A)$ region shown, explicit calculations a simple cubic lattice, depend on size shape anisotropy step distribution controls competition...

The fluorescence intensities and lifetimes of various no-phonon lines in ruby samples with 2.1 0.94% ${\mathrm{Cr}}^{3+}$ were studied from 13 to 700\ifmmode^\circ\else\textdegree\fi{}K. temperature dependences the numerous used determine energy levels two pair systems. relative single-ion ($R$) ($N$) are proportional Boltzmann factors ${e}^{\frac{\ensuremath{-}\ensuremath{\Delta}E}{\mathrm{kT}}}$, where $\ensuremath{\Delta}E$ is difference metastable states, at high temperatures but not low...

It is shown that diffusion of singlet excitons cannot explain the time dependence fluorescence intensity in tetracene-doped anthracene crystals; however, predictions a long-range energy-transfer mechanism can be made to agree with experimental results.

The widths and positions of the R N lines in heavily doped ruby have been measured at temperatures from 13° up to 450°K. results for temperature dependence linewidths are explained terms microscopic strains, Raman scattering phonons by impurity ions, direct phonon processes. lineshifts with due absorption emission virtual phonons. A Debye model is used different effective distributions linewidth lineshift Also distribution broadening pair (N) that single ion (R) lines.

Crystals of NaCl containing different concentrations ${\mathrm{Eu}}^{2+}$ and ${\mathrm{Mn}}^{2+}$ ions (the Eu concentration always being less than that Mn) were investigated by optical EPR spectroscopy. The results show ${\mathrm{Eu}}^{2+}$-${\mathrm{Mn}}^{2+}$ pairs form preferentially in this material highly efficient energy transfer occurs from the to near-neighbor ions. Over 99% are paired, these not significantly affected state aggregation Mn ions, although various samples evidence...

Laser-excited, time-resolved site-selection spectroscopy techniques were used to investigate energy transfer between ${\mathrm{Nd}}^{3+}$ ions in ${\mathrm{Y}}_{3}$${\mathrm{Al}}_{5}$${\mathrm{O}}_{12}$ and ${\mathrm{Y}}_{3}$${\mathrm{Ga}}_{5}$${\mathrm{O}}_{12}$ crystals. The results are consistent with a multistep diffusion type of the mechanisms for trapping both involving resonant two-phonon-assisted processes.