Effect of Br− ions on the F-center formation in KCl crystals under u.v. light irradiation

The relative efficiency of the F-center formation, Y_F in KCl crystals has been studied as a function of photon energy of u.v. light between 5.7 and 10.0 eV. Y_F is maximum at the peak of the absorption band due to the localized excitons at Br^? ions, and increases with Br^? concentration. Results suggest an important role of the localized excitons in the F-center formation.     

X-ray study of c-axis parameters in disordered stage II Agχ TiS2

X-ray measurements have been performed on disordered Stage II Ag_χ TiS₂ crystals with χ = 0.18 and 0.19. The c-axis structure was determined using the 00.l reflections for 4 ?l? 29. A principal result is that the intercalation of Ag⁺ between S layers produces unequal TiS distances in the adjacent TiS₂. The charge transfer to the Ti layer produces an expanded TiS distance adjacent to the Ag layer. The TiS distance away from the Ag ions is accordingly contracted. This effective (indirect) repulsive interaction between Ag⁺ and Ti may provide a mechanism for staging in these materials by keeping the Ag layers as far apart as possible.     

Optical properties of Tl2In2Se3S layered single crystals

The optical properties of Tl₂In₂Se₃S layered single crystals have been analyzed using transmission and reflection measurements in the wavelength region between 500 and 1100 nm. The optical indirect transitions with a band gap energy of 1.96 eV and direct transitions with a band gap energy of 2.16 eV were determined from analysis of absorption data at room temperature. Dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single-effective-oscillator model. The refractive index dispersion parameters – oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index – were found to be 4.67 eV, 45.35 eV, 1.38 × 10¹⁴ m ^{? 2} and 3.27, respectively. Transmission measurements were also performed in the temperature range 10–300 K. As a result of temperature-dependent transmission measurements, the rate of change in the indirect band gap with temperature, i.e. γ = ?5.6 × 10^?4 eV/K, and the absolute zero value of the band gap energy, E _gi(0) = 2.09 eV, were obtained.     

Analysis of ν2 of H2S

The infrared absorption spectrum of ν₂ of H₂S in the region from 1000 to 1500 cm^?1 was obtained with a resolution limit of <0.05 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 387 lines due to H₂³²S, 75 lines due to H₂³⁴S, and 15 lines due to H₂³³S, and have analyzed them using Typke's reduction of Watson's Hamiltonian. Slightly revised ground-state constants for the 32 isotope were obtained from a simultaneous fit of the microwave transitions observed by Helminger, Cook, and De Lucia, combined with weighted averaged ground-state combination differences formed from the infrared bands (010), (020), (100), (001), (110), (011), (210), and (111). The standard deviation for the fit was 0.0018 cm^?1 for the infrared data and 0.000032 cm^?1 for the microwave lines. Upper-state constants for the 32 isotope were obtained from a least-squares fit of the spectral lines of ν₂, keeping the ground-state constants fixed to the values determined by the combination difference fit. The standard deviation of the (010) line fit was 0.0017 cm^?1 for the 32 isotope. Ground-state and upper-state isotopic mass adjustment constants were determined in a simultaneous fit of lines of H₂³³S and H₂³⁴S, keeping the ground-state and upper-state constants for the 32 isotope fixed.     

Absorption spectrum of Cs2Mg(SO4)2 · 6H2O:Ni2+ single crystals

The absorption spectrum of Ni²⁺ doped in Cs₂Mg(SO₄)₂ · 6H₂O single crystals has been studied at room and liquid nitrogen temperatures in the range 7000–34000 cm^?1. The observed spectrum is satisfactorily interpreted in terms of cubic ligand field model including spin-orbit coulping. The ligand field parameters evaluated to best fit the observed spectrum are B = 955 cm^?1, C = 3572 cm^?1, Dq = 910 cm^?1 and ξ = 550 cm^?1. The non-ligand field band observed at 77K has been interpreted to be the superposition of vabrational mode of SO₄^2? radical on ₃T_1g(F) band.     

Infrared spectrum of CS2: “Hot” bands associated with the 2185 cm−1 band and evidence for the CS2 laser assignment

The 10⁰100⁰0 band of CS₂ has been measured with a resolution of 0.030 cm^?1. The following “hot” bands associated with this transition were also measured and analyzed: 11¹101¹0, 12⁰102⁰0, 12²102²0, 13³103³0, 20⁰110⁰0, 30⁰120⁰0, 21¹111¹0, and 22⁰112⁰0. In addition, the 10⁰100⁰0 bands of the isotopic species ¹³C³²S₂, ¹²C³²S³³S, and ¹²C³²S³⁴S were measured in natural abundance. With the results of these measurements it is shown that the 02⁰112⁰0 transitions do indeed coincide with the CS₂ laser transitions, as do the 00⁰110⁰0 transitions. New arguments are given favoring the latter assignment.     

High-temperature infrared spectrum of HCN near 3300 cm−2

The infrared absorption of HCN near the fundamental band at 3311 cm^?1 has been measured at temperatures up to 1200 K. Transitions involving high rotational states (up to J = 62) have been measured. These give an improved value for the sextic centrifugal distortion term H₀. Many hot-band transitions have been observed and assigned to transitions originating in vibrationally excited states up to 4000 cm^?1 above the ground state. These measurements give new data on vibrational states involving moderately high bending quantum numbers and indicate that new terms are needed to fit the ro-vibrational energy levels.     

The infrared spectra of 12C32S, 12C34S, 13C32S,and 12C33S

Using a tunable diode laser spectrometer, the infrared absorption spectra of four isotopic species of carbon monosulfide have been observed in the positive column of a dc discharge of CS₂ and Ar. The wavenumbers of 115 vibration-rotation transitions between 1180.5 and 1266.1 cm^?1 have been measured. These lines were assigned to the 1-0, 2-1, 3-2, and 4-3 bands of ¹²C³²S, the 1-0 and 2-1 bands of ¹²C³⁴S and ¹³C³²S, and the 1-0 band of ¹²C³³S. These new data have been combined with the previous infrared and microwave results to determine Dunham coefficients (Y_ij), the Dunham potential expansion constants (a₀,a₁,a₂,a₃, and a₄), and the classical turning points by the RKR method.     

Analysis of ν2 of D2S

The infrared spectrum of ν₂ of D₂S was recorded from 740 to 1100 cm^?1 on the University of Denver 50-cm FTIR spectrometer system. We have assigned 655 transitions from D₂³²S and 129 from D₂³⁴S, and have analyzed them using Watson's A-reduced Hamiltonian evaluated in the I^r representation. We used the recently published D₂³²S and D₂³⁴S ground state Hamiltonian constants [C. Camy-Peyret, J. M. Flaud, L. Lechuga-Fossat and J. W. C. Johns, J. Mol. Spectrosc.109, 300–333 (1985)]. Upper state Hamiltonian constants were obtained from a fit of the ν₂ transitions, keeping the ground state constants fixed while varying the upper state constants. The standard deviation of the D₂³²S ν₂ fit is 0.0025 cm^?1. The standard deviation of the D₂³⁴S ν₂ fit is 0.0041 cm^?1.     

The ν9 band of diazirine,H2CN2, by Doppler-limited Fourier transform infrared spectroscopy

The Doppler-limited infrared spectrum of diazirine was recorded using a high-information Fourier transform spectrometer with a resolution of 0.0054 cm^?1. The rovibrational structure of the ν₉ fundamental (CH₂ rocking) at 1124.9144 cm^?1, which is a C-type band, was analyzed in detail with extensive use of spectrum simulation and correlation diagrams. The molecular constants for the upper energy level of this band were obtained from the overall rovibrational assignment of more than 2000 transitions, which cover the region from 1070 to 1220 cm^?1.     

Absorption spectra of Bi3+ and Fe3+ in Y3Ga5O12

The absorption spectra of Y₃Ga₅O₁₂:(Fe³⁺), Y₃Ga₅O₁₂:(Bi³⁺) and Y₃Ga₅O₁₂:(Bi³⁺, Fe³⁺) are presented to 40,000 cm^-1. Assignments are discussed and the transitions analysed in terms of their involvement in the large Faraday rotation observed in bismuth substituted iron garnets.     

Heterodyne frequency measurements of carbonyl sulfide transitions at 26 and 51 THz. Improved OCS,O13CS,and OC34S molecular constants

Heterodyne frequency measurements were made on selected absorption features of carbonyl sulfide (OCS) near 26 THz (860 cm^?1) and 51 THz (1700 cm^?1). Frequency differences were measured between a tunable diode laser (TDL) locked to carbonyl sulfide absorption lines and either a stabilized ¹³CO₂ laser or a CO laser which was referred to stabilized CO₂ lasers. These measurements are combined with conventional TDL measurements and published microwave measurements to obtain new, more reliable molecular constants for OCS, O¹³CS, and OC³⁴S. New frequency measurements are given for nine CO laser transitions between 1686 and 1726 cm^?1.     

Preparation of amorphous films of superionic conducting glasses in systems AgIAg2MoO4 and AgIAg2OB2O3

Thermal evaporation, flash evaporation and rf-sputtering techniques were applied to the preparation of amorphous films of superionic conducting glasses in the systems AgIAg₂MoO₄ and AgIAg₂OB₂O₃. The flash-evaporated films were amorphous and showed very high conductivities, about 2 × 10^?2S/cm for the AgIAg₂MoO₄ and about 5 × 10^?3S/cm for the AgIAg₂OB₂O₃ at room temperature, and gave a Ag⁺ transport number of unity. The thermal evaporation method produced crystalline-phase included films. The rf-sputtered films were amorphous by X-ray diffraction and the transport number of Ag⁺ ions was smaller than unity (about 0.9). Thus flash evaporation was concluded to be the most suitable method for preparing amorphous films of superionic conducting glasses.     

Absorption of Dy3+ and Nd3+ ions in BaR 2F8 single crystals

The Dy³⁺ absorption and excitation spectra of BaY₂F₈ and BaYb₂F₈ single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4f-5d transitions in the range (56–78) × 10^?3 cm^?1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50–56) × 10^?3 cm^?1. The Nd³⁺ absorption spectra of BaY₂F₈ single crystals are studied in the range (34–82) × 10^?3 cm^?1 at 300 K for different crystal orientations.     

X-ray diffraction, vibrational and photoluminescence studies of the self-organized quantum well crystal H3N(CH2)6NH3PbBr4

We have prepared new semiconductor H₃N(CH₂)₆NH₃PbBr₄ crystals which are self-assembled organic-inorganic hybrid materials. The grown crystals have been studied by X-ray diffraction, infrared absorption and Raman spectroscopy scattering. We found that the title compound, abbreviated 2C₆PbBr₄, crystallizes in a two-dimensional (2D) structure with a P2₁/a space group. In the inorganic semiconductor sub-lattice, the corner sharing PbBr₆ octahedra form infinite 2D chains. The organic C₆H₁₈N₂⁺ ions form the insulator barriers between the inorganic semiconductor layers. Such a packing leads to a self-assembled multiple quantum well structure. Raman and infrared spectra of the title compound were recorded in the 50-500 and 400-4000 cm⁻¹ frequency regions, respectively. The assignment of the observed Raman lines was performed by comparison with the homologous compounds. Transmission measurements on thin films of 2C₆PbBr₄, obtained by the spin coating method, revealed a strong absorption peak at 380 nm. Luminescence measurements showed an emission line at 402 nm associated with radiative recombinations of excitons confined within the PbBr₆ layers. The electron-hole binding energy is estimated at 180 meV.     

Refractive index, oscillator parameters and temperature-tuned energy band gap of Tl4In3GaS8-layered single crystals

Transmission and reflection measurements in the wavelength region 450-1100 nm were carried out on Tl₄In₃GaS₈-layered single crystals. The analysis of the room temperature absorption data revealed the presence of both optical indirect and direct transitions with band gap energies of 2.32 and 2.52 eV, respectively. The rate of change of the indirect band gap with temperature dE_gi/dT=-6.0×10⁻⁴ eV/K was determined from transmission measurements in the temperature range of 10-300 K. The absolute zero value of the band gap energy was obtained as E_gi(0)=2.44 eV. The dispersion of the refractive index is discussed in terms of the Wemple-DiDomenico single-effective-oscillator model. The refractive index dispersion parameters: oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index were found to be 4.87 eV, 26.77 eV, 8.48×10¹³ m⁻² and 2.55, respectively.     

The ν2 and ν4 bands of AsH3

The infrared absorption of arsine, AsH₃, between 750 and 1200 cm^?1 has been recorded at a resolution of 0.006 cm^?1. Altogether 2419 transitions, including nearly 700 “perturbation allowed” transitions with Δ∥k ? l∥ = ±3, ±6, and ±9, have been assigned to the ν₂(A₁) and ν₄(E) bands. Splitting of the transitions for K″ = 3, 6, and 9 was also observed. To fit the rotational pattern of the v₂ = 1 and v₄ = 1 vibrational states up to J = 21, all the experimental data were analyzed simultaneously on the basis of a rovibrational Hamiltonian which took into account the Coriolis interaction between ν₂ and ν₄ and also included several essential resonances within them. The derived set of 38 significant spectroscopic parameters reproduced the 2328 transition wavenumbers retained in the final fit within the accuracy of the experimental measurements.     

The electronic absorption spectra of [(CH3)3NH] MnCl3.2H2O single crystals

The electronic absorption spectra of [(CH₃)₃NH] MnCl₃.2H₂O single crystals are reported in the 15,000–45,000 cm^-1 region. In addition to the normally studied sextet → quartet transitions, special attention has been paid to the sextet → doublet transitions. Crystal field parameters evaluated (including the Trees' correction factor) to fit the observed spectra are B = 800, C = 2900, Dq = 680, and α = 76 cm^-1.     

Direct and indirect optical transitions in Zn3P2

Absorption measurements were made on single crystals of Zn₃P₂ at temperatures of 300, 80 and 5 K, and photo-voltage spectral responses-were measured at 300 K for Au- and In---Zn₃P₂ contacts. Interband absorption was interpreted as a process involving three mechanisms: (1) indirect transitions from the valence band at the Γ point, (2) either excitations from acceptor level to the conduction band at the Γ point, or second indirect transitions associated with the creation of excitons, and (3) band-to-band direct transitions at the Γ point. The effect of the lighting configuration on spectral PV plots is also discussed, and the origin of two peaks of PV responses is interpreted as being in accordance with optical data. The indirect energy gap has been estimated as 1.315eV at 300 K and 1.335 eV at 80 and 5 K, and the direct one as 1.505, 1.645 and 1.685 eV at 300, 80 and 5 K, respectively.     

Simultaneous analysis of the ν1, ν4, 2ν2, ν2 + ν5, and 2ν5 infrared bands of 12CH3F

The Fourier-transform spectrum of CH₃F from 2800 to 3100 cm^?1, obtained by Guelachvili in Orsay at a resolution of about 0.003 cm^?1, was analyzed. The effective Hamiltonian used contained all symmetry allowed interactions up to second order in the Amat-Nielsen classification, together with selected third-order terms, amongst the set of nine vibrational basis functions represented by the states ν₁(A₁), ν₄(E), 2ν₂(A₁), ν₂ + ν₅(E), 2ν₅⁰(A₁), and 2ν₅^±2(E). A number of strong Fermi and Coriolis resonances are involved. The vibrational Hamiltonian matrix was not factorized beyond the requirements of symmetry. A total of 59 molecular parameters were refined in a simultaneous least-squares analysis to over 1500 upper-state energy levels for J ≤ 20 with a standard deviation of 0.013 cm^?1. Although the standard deviation remains an order of magnitude greater than the precision of the measurements, this work breaks new ground in the simultaneous analysis of interacting symmetric top vibrational levels, in terms of the number of interacting vibrational states and the number of parameters in the Hamiltonian.