Far U.V. absorption spectra of manganese halides between 20 and 67 eV.

The absorption spectra of evaporated thin films of MnF₂, MnCl₂, MnBr₂ have been measured in the energy range 20–67 eV. The onset of the absorption of 3p Mn²⁺ is about 50 eV. At lower energies, the structures may be attributed to transitions from 2s F^-, 4s Br^- and 3d Mn²⁺ levels.     

The reflection spectra of cuprous halides at low temperature in the 4.5 to 30 eV range and related band structures

In a previous paper, we proposed a band scheme for C u C l established with the help of the reflection spectra measured at low temperature up to 30 eV. Now we are extending this study to CuBr and CuI where the optical data are obtained in the same way. Some experimental features are characterized, through the whole sequence, by their thermal behaviour and by the evolution of their structure in relation to the increasing spin orbit separation from CuCl to CuI. This study also shows the similarity of the band schemes in the three halides and the interest of optical measurements, at low temperature and in a wide energy range, for band scheme determination.     

The reflection spectra of cuprous halides in the 4.5–7.5 eV range

The reflection spectra of cuprous halides have been measured on cleaved samples at various temperatures from 300 K up to 6 K. The experimental device is improved by a minicomputer based data acquisition system. The appearance of structures at low temperature, the evolution of the spectra versus temperatures permit us to interprete some experimental features in terms of a band structure scheme where the valence bands are calculated in the tight binding approximation, the spin orbit splitting being introduced as a perturbation.     

Absorption,excitation and fluorescence spectra of thallium activated cesium bromide

Absorption, excitation and fluorescence spectra of T1⁺ doped cesium bromide have been investigated at various thallium concentrations. At very low thallium concentration two absorption bands are obtained at 225 nm and 264 nm. With rise of thallium concentration additional absorption bands are obtained at 230, 244, 258, 270 and 285 nm. A single bell-shaped fluorescence band at 357 nm in the ultraviolet region is obtained at low thallium concentration. Two additional visible fluorescence bands appear at 440 and 540 nm with rise in thallium content. The excitation spectra for ultraviolet emission band and visible emission bands are found to be different. Accordingly the ultraviolet emission band is attributed to the characteristic A emission in T1⁺ ion and the visible bands are attributed to dimer centers havingD _4h site symmetry.     

Emission and excitation spectra of IF in solid argon at 12 K

The interhalogen, IF, has been synthesized by vacuum ultraviolet photolysis of CHF₂I and CHFI₂ and subsequently trapped in solid argon at 12 K. The $\text{B}{}^3\text{π}{}_0{}^{\mathrm{+}}\text{-X}{}^1\text{Σ}$ transition was observed in emission and dye laser excitation experiments with the origin near 18 688 cm^?1 and average ground- and excited-state spacings of 573 and 380 cm^?1, respectively. These data are compared to the gas phase results.     

40.81 eV photoelectron spectroscopy of the thallous halides

Photoelectron spectra (using 40.81 eV photons) of TlF, TlCl, TlBr and TlI are presented. Absolute binding energies of the outermost halogen np levels with respect to the vacuum level and the energy separations between the thallium 5d_5/2 level and the halogen np level are compared with the corresponding energies predicted using the Born model for ionic solids. The thallium ion ²D_5/2 and ²D_3/2 final states display a non-statistical branching ratio and this is explained in terms of the relative photoionization cross-sections of d_5/2 and d_3/2 electrons. Structure in the spectrum of TIF is interpreted in terms of molecular orbital-like states.     

Photoelectron spectra of halides

High resolution photoelectron spectra, obtained with He I (584 Å) resonance radiation, are reported for ClF, ClF₃, BrF₃ and BrF (partial spectrum). In some cases Ne I (736–744 Å) radiation has also been used. Spinorbit and vibrational fine structure is resolved for the ground ²II states of ClF⁺ and BrF⁺; values obtained for ClF⁺ and ζ = 630 cm^-1, v′ = 870 cm^-1, and for BrF⁺ ζ = 2600 cm^-1, v′ = 750 cm^-1. From the vibrational envelope of the X ²∏ states, a bond length change of δr _e (-)0·10 Å for ClF⁺ and BrF⁺ is estimated. Ab initio SCF-MO calculations for ClF and ClF₃ are used to aid in the interpretation of the spectra via Koopmans' theorem. A considerable amount of charge delocalization in the trifluorides is inferred from the photoelectron spectra, and this is borne out by the calculations.     

Luminescence of interstitial atomic hydrogen in cesium halides

Interstitial atomic hydrogen centres show no emission in the pure alkali halides of the NaCl structure. In pure cesium-halides, however, a luminescence band at about 1.1 eV was found. From the excitation spectrum the absorption bands could be identified. In a mixed configuration where the hydrogen atom is surrounded by one Cl^? or Br^? and one I^? ion along [100] there are 6 absorption and 2 emission bands. The absorption and emission are qualitatively interpreted as a simple charge-transfer model and reasons for the radiative and non-radiative transitions from the excited states are discussed.Atomare Wasserstoffzentren auf Zwischengitterplatz zeigen keine Emission in den reinen Alkalihalogeniden der NaCl-Struktur. In den reinen Cäsiumhalogeniden findet man jedoch eine Lumineszenzbande bei ca. 1,1 eV. Aus dem Anregungsspektrum konnten die Absorptionsbanden identifiziert werden. In einer gemischten Konfiguration, bei der das Wasserstoffatom von einem Cl^?, bzw. Br^? und einem I^? Ion in der [100]-Richtung umgeben ist, gibt es 6 Absorptions- und 2 Emissionsbanden. Die Absorption und Emission werden qualitativ mit Hilfe eines einfachen Charge-Transfer Modells gedeutet und Gründe für die strahlenden und nichtstrahlenden Übergänge aus den angeregten Zuständen werden diskutiert.     

Photoionization and threshold photoelectron-photoion coincidence study of allene from onset to 20 eV

The photoionization efficiency curves for allene and its fragments C₃H₃⁺, C₃H₂⁺ and C₃H⁺ are given from threshold to 20 eV. The threshold photoelectron spectra and breakdown curves are given over the same energy span. The adiabatic ionization potential is determined to be 9.69 ±0.01 eV and the heats of formation of the fragments are derived from the appearance potentials. Autoionization is found to be an important factor in the parent ionization and fragmentation.     

Optical properties of InSe from 2 eV to 25 eV

The reflectivity spectrum of InSe between 2 and 25 eV is reported. From experimental results the optical functions are computed and a conduction band density of states is proposed. A comparison is made with a previous pseudopotential band structure calculation.     

Cathodo-luminescence spectra of alkali halides

Cathodo-luminescence spectra of fourteen alkali halides and of some mixed crystals of NaCl and KCl have been studied. The spectra show broad structureless bands. In some ten halides it is possible to find a strong band whose peak position shifts towards longer wavelengths as the inter-atomic distance increases. For pottasium halides the relationship λ_max=1380d, where “d” is the inter-atomic distance, holds approximately but is not generally true. A mechanism of cathodo-luminescence in alkali halides has been postulated, and an interpretation of the above band and of some NaCl bands has been made on that basis.     

Raman spectra of alkali halides

In this article, we present a comparative study of the Raman spectra of alkali halides in relation to the lattice dynamics ofBorn andRaman. It is shown that the experimentally observed limit of the second-order spectra in almost all the cases can be explained well by the Lyddane-Sachs-Teller relation. It is also seen, while, an explanation of the second-order Raman spectrum of a crystal of diamond or zinc blende structure requires the frequencies from the critical points,W, Γ, X andL inBorn's analysis, the frequencies fromΓ, X andL alone are sufficient and necessary for an interpretation of the same onRaman's model. Some similarities in the determination of the long wave properties of crystals like elastic constants and limiting frequencies of the lattice vibrations in the symmetry directions in both the models are pointed out.     

Vibrational spectra of cesium tellurate phosphate

The infrared and Raman spectra of cesium tellurate phosphate (Te(OH)₆·Cs₂HPO₄), a compound containing two anions, are recorded and analysed. It has been found that the two anions Te(OH)₆ and HPO₄ coexist in the crystal almost independently without affecting each other. The hydrogen atom is loosely bonded to the oxygen atom of the phosphate ion and hence the phosphate ion exists as distorted PO³⁻₄ tetrahedron rather than HPO²⁻₄ ion.     

Compression curves of the cesium halides using murnaghan logarithmic equation

The pressure derivatives of the adiabatic bulk moduli of the cesium halides are evaluated from the pressure derivatives of their elastic constants C₁₁ and C₁₂. Murnaghan's logarithmic equation is then used to determine the compression curves of these solids. The agreement between the calculated and experimental compression-ratio values for these halides of cesium is good.     

Optical reflection spectra of cadmium halides

The reflection spectra have been measured at liquid helium temperature in the region 4–11.5 eV for CdCl₂ and CdBr₂ crystals. Exciton bands observed around the optical gap are associated with the halogen ion excitation under the influence of the strong crystal field. Characteristic sharp lines are also observed in the deep interband energy regions.