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.     

Mößbauereffekt in FeCl2, FeSO4 und FeSO4 · 7 H2O

Mößbauereffect measurements were performed with FeCl₂, FeSO₄ and FeSO₄ · 7 H₂O in the temperature range between 5 and 300 ?K. The quadrupole splittings at 5 ?K were determined to be (1.300±0.027) mm/sec, (3.650±0.053) mm/sec, and (3.350±0.053) mm/sec respectively. From the temperature dependence of the quadrupole splittings it follows that in FeCl₂ the energy of the excited 3d-electron-level isδ=150 cm^?1, in FeSO₄ δ ₁=360 cm^?1 andδ ₂=1680 cm^?1 and in FeSO₄ · 7 H₂Oδ ₁=480 cm^?1 andδ ₂=1300 cm^?1. The magnitudes of the magnetic field at the iron nucleus at 5 ?K are (202±8) kOe for FeSO₄ and (0±4) kOe for FeCl₂.     

Luminescence spectroscopy of high-energy 4f 11 levels of Er3+ in fluorides

The 4f¹¹ energy levels of Er³⁺ in LiYF₄ in the spectral region 39000–65000 cm^?1 have been studied. The agreement between experimental energy levels, obtained from luminescence excitation spectra, and calculated energy levels is good. Luminescence originating from high-lying energy levels has been investigated. Emission from the states ⁴D_1/2 (～47 200cm^?1), ²F(2)_7/2 (～54700cm^?1) and ²F(2)_5/2 (～63 300cm^?1) is observed. ²F(2)_5/2 emission occurs for Er³⁺ in LaF₃, where the ²F(2)_5/2 level is situated just below the lowest 4f¹⁰5d state, but also for Er³⁺ in LiYF₄, where it lies in between the two lowest 4f¹⁰5d states.     

High resolution infrared spectrum of the ν4 band of DCCF

The bending vibration-rotation band ν₄ of DCCF was studied. The measurements were carried out with a Fourier spectrometer at a resolution of about 0.03 cm^?1. The constants B₀=0.29141(1)cm^?1, α₄=?5.02(2)×10^?4cm^?1, q₄=4.52(3)×10^?4cm^?1, and D₀=9.2(4)×10^?8cm^?1 were derived. The rotational analysis of the “hot” bands 2ν₄(Δ) ← ν₄(II) and 2ν₄(Σ⁺) ← ν₄(II) was performed. In addition, the “hot” bands ν₄ + ν₅ ← ν₅ were assigned. A set of vibrational constants involved was derived.     

UV and VUV spectroscopic study of Na0.4Y0.6F2.2 crystals doped with rare-earth ions

The short-wavelength transmission spectra of Na_0.4 R _0.6F_2.2 crystals with R = Y, Yb, or Lu have been investigated. For these crystals, the VUV transmission cutoffs are 78750, 58820, and 75200 cm^?1, respectively. The 4f ⁿ–4f ^n?15d absorption and excitation spectra of Na_0.4Y_0.6F_2.2 crystals activated with Ce³⁺, Pr³⁺, Nd³⁺, Er³⁺, Tm³⁺, and Yb³⁺ ions have been analyzed in the range 30000–80000 cm^?1. The energy positions of the lowest levels of the 4f ^n?15d configurations of these ions in the fluorite crystal matrix Na_0.4Y_0.6F_2.2 are determined. The absorption band in the spectral range 60600–70000 cm^?1 in Na_0.4(Y, Yb)_0.6F_2.2 crystals is due to the charge transfer from F^? to Yb³⁺. It is shown that the environmental symmetry of Ce³⁺ ions in Na_0.4R_0.6F_2.2 (R = Y, Yb, Lu) crystals is almost identical.     

Vibration-rotation spectra of CH3CN: The ν7 band and its hot bands near 1040 cm−1

Infrared spectra of CH₃CN were measured in the range 170–600 cm^?1 with a Fourier transform spectrometer (0.06 cm^?1 resolution) and several small portions in the range 1020–1065 cm^?1 with a tunable Pb_1?xSn_xTe diode laser spectrometer (0.001 cm^?1 resolution). The ν₇ band was analyzed by taking account of local Fermi resonance with 3ν₈¹, and the following parameters were determined: ν₇ = 1041.8446(15) cm^?1; 3ν₈¹ =1077.88(5) cm^?1; and ∥k₇₈₈₈∥ = 1.98(1) cm^?1. Two hot bands in the ν₇ band region, i.e., (ν₇ + ν₈)² ? ν₈¹ and ν₆¹ ? ν₈¹, were also analyzed, and ν₈ = 365.05(5) cm^?1 and ζ₈ = 0.874(1) were determined by use of the observed transitions of the ν₇ + ν₈ and ν₆ bands.     

Rotational study and hyperfine effects of the (0,0) band of the B2Σ-X2Σ system of ScS

Rotational analysis of the (0,0) band of the B²Σ-X²Σ transition of ScS is reported. Spectrographic illustration of a hyperfine coupling transition in the ground state is demonstrated for the first time. This enables an order of magnitude to be obtained for γ″ (～0.003 cm^?1). The results for the other constants were: X state: B″ = 0.1971 cm^?1, D″ = 5 × 10^?8cm^?1, 4b = 0.23 cm^?1 (equal to that for ScO within the limits of measurement uncertainty); B state: B′ = 0.1853 cm^?1, D′ = 6 × 10^?8cm^?1, γ′ = ?0.0594 cm^?1, which can be compared with p_A²Π = 0.060 cm^?1. It was found that the two excited states A²Π and B²Σ constitute an excellent example of pure precession (p_pp = 0.058 cm^?1, and this enables the vibrational levels of A²Π to be numbered.     

The role of anion vacancy migration in lead halide photolysis

From the electrical conductivity of meltgrown Pb₂NaI single crystals for the first time mobility of the iodide ion vacancies along the c-axis is calculated (temperature region 340–540 K). It is shown that the transition from the colour centre mode (CCM) to the print-out mode (POM) of the photolysis of Pb₂ (X = Cl, Br, I) occurs when the anion vacancy mobility in PbCl₂ and PbBr₂ exceeds the value 1.0 × 10^?8cm²V^?1sec^?1, and in PbI₂ the value 8.1 × 10^?8cm²V^?1sec^?1.     

Coherent Stokes and anti-Stokes Raman spectra of the ν1 (A1) and ν2 (E) bands of SF6 and UF6

Coherent Stokes and anti-Stokes Raman scattering are used to study the ν₁ and ν₂ spectral band profiles of UF₆ and SF₆. Most of the observed SF₆ “hot” bands are assigned, leading to evaluations of the anharmonicity constants X_ij: X₁₂ = ?(2.80 ± 0.30) cm^?1, X₁₄ = ?(1.00 ± 0.15) cm^?1, X₁₅ = ?(1.00 ± 0.15) cm^?1. For UF₆, a tentative assignment of the “hot” bands is made: X₁₂ = ?(1.80 ± 0.30) cm^?1, X₁₃ = ?(1.60 ± 0.30) cm^?1, X₁₄ = ?(0.20 ± 0.10) cm^?1, X₁₅ = ?(0.25 ± 0.10) cm^?1, and X₁₆ = ?(0.10 ± 0.05) cm^?1. Parameters such as the vibration-rotation coupling constants are determined. For SF₆: α = (7 ± 2) × 10^?5 cm^?1 for the ν₂ band and α = ?(1.02 ± 0.01) 10^?4 cm^?1 for the ν₁ band. The calculated spectral profiles of the coherent Stokes or anti-Stokes spectra, which are in good agreement with experimental results, give values for the resonant and nonresonant parts of the susceptibility in both molecules. They also show, in some cases, the influence of neighboring combination bands.     

Fourier transform infrared spectrum of thioketene,CH2CS

The FTIR spectrum of the unstable species thioketene, CH₂CS, has been detected in a vapor-phase flow pyrolysis system. The region 800–3500 cm^?1 has been surveyed with a resolution of 1 cm^?1, enabling the frequencies of the six fundamentals which lie above 800 cm^?1 to be determined. Certain bands have been studied under very high resolution and the results of the analyses of the perpendicular bands ν₇ and ν₃ + ν₈, observed with a resolution of 0.01 and 0.005 cm^?1 respectively, are presented. The ground state constant, A₀, is determined as 286 453.60(58) cm^?1.     

Far-infrared rotational spectra of some freons; chlorotrifluoromethane,dichlorodifluoromethane, and trichlorofluoromethane

The far-infrared rotational spectra of chlorotrifluoromethane, dichlorodifluoromethane, and trichlorofluoromethane have been observed with an interferometric (Fourier transform) spectrometer in the region 10–40 cm^?1 at a resolution of 0.07 cm^?1. CCl₂F₂ exhibits a continuum spectrum at this resolution, but symmetric top rotational fine structure is observed for CClF₃ and CCl₃F. Isotope splitting is also observed in CClF₃, and analysis yields the rotational constants for C³⁵ClF₃ of B₀ = 0.11112 cm^?1, D_J = 1.6 × 10^?8cm^?1; and for C³⁷ClF₃, B₀ = 0.10835 cm^?1, D_J = 1.5 · 10^?8cm^?1. Isotopic shifts can be allowed for in CCl₃F to yield constants for C³⁵Cl₃F of B₀ = 0.0821 cm^?1, D_J = 1 × 10^?8cm^?1. These values are all in agreement with those deduced from microwave studies of the low J transitions apart from B₀ for C³⁵ClF₃, where the difference is outside the expected experimental error.     

Analysis of the ν6(A″2) band of cyclopropane-d6 recorded under high resolution

The parallel band ν₆(A″₂) of C₃D₆ near 2336 cm^?1 has been studied with high resolution (Δν = 0.020 – 0.024 cm^?1) in the infrared. The band has been analyzed using standard techniques and the following parameters have been determined: B″ = 0.461388(20) cm^?1, D″_J = 3.83(17) × 10^?7 cm^?1, ν₀ = 2336.764(2) cm^?1, α^B = (B″ ? B′) = 8.823(12) × 10^?4 cm^?1, β^J = (D″_J ? D′_J) = 0, and α^C = (C″ ? C′) = 4.5(5) × 10^?4 cm^?1.     

Adsorption of lead on low-index planes of tungsten

Using probe-hole field emission microscopy the effect of adsorbed lead on the work function of the 100 and 110 planes of tungsten hasbeen studied and compared with the findings of Bauer et al. who studied the same system using LEED/Auger techniques. The effect of lead on the average work function $\text{}\text{?}$gf and that of (211) is also reported. Sub-monolayer lead increases φ(211) and this is ascribed to formation of a lead-tungsten dipole, the lead being negatively charged, with dipole moment 0.035 × 10^?30 C-m and polarizability 2.0 ų. On (110) lead reduces φ and behaves as a dipole with positively charged lead of moment 0.15 × 10^?30 C-m and polarizability 2.5 ų. φ(100) is also observed to decrease at low coverages equilibrated at low temperatures. This contrasts with Bauer's findings but is considered to result from failure of the Fowler—Nordheim model. With increasing lead coverage on all planes φ(hkl) tends to a constant value φ_sat. By comparison with Bauer et al. we can identify φ_sat on (110) as a compressed monolayer of lead. Likewise φ_sat produced by low temperature (～450 K) spreading on (100) is also associated with a compressed (1 × 1) structure. The lower value of φ(100) produced at higher temperatures (～850 K) is identified with the microfacetted surface observed by Bauer et al. Lead is observed to be absent from (110) when mean adatom densities as high as 8 × 10¹⁴ atoms cm^?2 are thermally equilibrated, and this is shown to result from the relatively low binding energy of lead on (110). The general agreement between the present findings and those of Bauer lends confidence to the belief that both techniques can detect the same behaviour despite the very large (10¹⁰) difference in the size of the area examined.     

Mass transport in cuprous oxide

The chemical diffusion coefficient of Cu₂O has been obtained for an oxygen partial pressure near 5 10^?4 atm as a function of the temperature in the range 700–900°C D? = 1 62 10^?4 exp(?5140 ± 600 cal mol ^?1)/RT cm²s^?1 This was easily achieved according to the electrochemical method used for the preparation of gaseous mixtures whose Po₂; is lower than 10^?5 atm The slight difference observed with the previously published results by Maluenda, and obtained for Po₂ values which increase with T between 10^?4 and 0.21 atm, may be due to an oxygen partial pressure effect already observed in the case of CoO. An ambipolar treatment of the chemical diffusion, in the case of p-type semiconductor M_aO_b, oxides, has allowed us to express the chemical diffusion coefficient as a function of the concentration of the prevailing defects and of their diffusion coefficient In the case where the prevailing defects are cationic vacancies α times ionized we have shown that the expression D? = (1 + α)D_vα can be generalized to the A₂O compounds This set of results has allowed us, according to the copper self diffusion data obtained recently by Peterson etal, to estimate the apparent enthalpy of formation of the catiomc vacancies ΔH_f 23 ± 0 8 kcal mol^?1.     

Vibrational spectra and force constants of symmetric tops: High-resolution spectra of H374Ge35Cl in the ν1ν4 region near 2100 cm−1

The gas-phase infrared spectrum of monoisotopic H₃⁷⁴Ge³⁵Cl has been studied in the ν₁, ν₄ region near 2100 cm^?1 with a resolution of 0.008 cm^?1. Rotational fine structure for ΔJ = ±1 branches has been resolved for both fundamentals. ν₁ (a₁), 2119.977 03(19) cm^?1; and ν₄ (e), 2128.484 65(8) cm^?1 are weakly coupled by Coriolis x,y resonance, Bξ_1,4^y 2.6 × 10^?3 cm^?1, and l-type resonance within ν₄, q₄⁽⁺⁾ ?8.4 × 10^?6 cm^?1, has been observed. An extended Fermi resonance with ν₅^±1 + 2ν₆^±2, which mainly affects the kl = ?14 and ?15 levels of ν₄, has been detected and analyzed. In addition, several weak and local resonances perturb essentially every K subband of ν₄ and some of ν₁, and a qualitative model is proposed to account for the features observed in the spectrum. Disregarding the transitions involved in local perturbations, the rms deviation of the fit to the remaining 2021 lines is σ = 1.34 × 10^?3 cm^?1.     

Magnetic moment relaxation of a shallow acceptor center in heavily doped silicon

Results of studying the temperature dependence of the residual polarization of negative muons in crystalline silicon with germanium (9×10 ¹⁹ cm ^?3 ) and boron (4.1×10 ¹⁸ , 1.34×10 ¹⁹ , and 4.9×10 ¹⁹ cm ^?3 ) impurities are presented. It is found that, similarly to n-and p-type silicon samples with impurity concentrations up to ～10 ¹⁷ cm ^?3 , the relaxation rate ν of the magnetic moment of a _μ Al acceptor in silicon with a high impurity concentration of germanium (9×10 ¹⁹ cm ^?3 ) depends on temperature as ν～T ^q , q≈3 at T=(5–30) K. An increase in the absolute value of the relaxation rate and a weakening of its temperature dependence are observed in samples of degenerate silicon in the given temperature range. Based on the experimental data obtained, the conclusion is made that the spin-exchange scattering of free charge carriers makes a significant contribution to the magnetic moment relaxation of a shallow acceptor center in degenerate silicon at T?30 K. Estimates are obtained for the effective cross section of the spin-exchange scattering of holes (σ _h ) and electrons (σ _e ) from an Al acceptor center in Si: σ _h ～10^?13 cm² and σ _e ～8×10^?15 cm² at the acceptor (donor) impurity concentration n _a (n _d )～4×10¹⁸ cm^?3.     

Infrared spectroscopy of the intermediate-valence semiconductor YbB12

The dynamic conductivity and permittivity spectra of the intermediate-valence compound YbB₁₂ are measured in the frequency range (6–10⁴) cm^?1 (quantum energy 0.75 meV-1.24 eV) at temperatures of 5–300 K. Analysis of the spectral singularities associated with the response of free charge carriers has made it possible for the first time to determine the temperature dependences of their microscopic parameters, viz., concentration, effective mass, relaxation frequency and time, mobility, and plasma frequency. It is shown that the relaxation frequency decreases upon cooling from 300 K to the coherence temperature T ^* = 70 K for YbB₁₂, which is mainly associated with the phonon mechanism of scattering of charge carriers. For cooling below the coherence temperature T ^* = 70 K, the temperature dependence of the relaxation frequency for charge carriers of the Fermi-liquid type is found to be γ ～ γ₀ + T ², while their effective mass and relaxation time increase, respectively, to m ^*(20 K) = 34m ₀ (m ₀ is the free electron mass) and τ(20 K) = 4 × 10^?13 s, indicating the establishment of coherent scattering of carriers from localized magnetic moments of the f centers. At a temperature of T = 5 K, the conductivity spectrum contains an absorption line at a frequency of 22 cm^?1 (2.7 meV); the origin of this line can be associated with the exciton-polaron bound state. Since such a state was observed earlier in other intermediate-valence semiconductors (such as SmB₆, TmSe_1?x Te, and (Sm, Y)S), it is probably typical of this class of compounds.     

Coupling of the CDW and the water mode in K2Pt(CN)4Br0.3⋯3.2H2O

In previous work we have observed the amplitude mode of the charge density wave (CDW) in K₂Pt(CN)₄Br_0.3?3.2H₂O (KCP) by means of Raman scattering. New measurements made on deuterated material, K₂Pt(CN)₄Br_0.3?3.2D₂O (KCP1), show the same mode but shifted from 44 to 38 cm_?1, maintaining the symmetry properties and temperature dependence of frequency and linewidth. This considerable isotope effect is interpreted in terms of a coupling of the CDW with the water stretching mode, which by the deuteration is shifted from 3494 cm^?1 in KCP to 2560 cm^?1 in KCP1 according to the change in atomic mass. Both of these modes exhibit A₁(z) symmetry. At 5 K the resulting decoupled frequency of the CDW amplitude mode is 57 cm^?1, and the coupling energy about 140 cm^?1. A discussion of the temperature dependence of various important quantities is given. The present results show that the water molecules, which are located in between the Pt chains are strongly involved in the eigenvector of the CDW amplitude mode.     

Investigation of the temperature dependence for the spectra of supercooled water in the middle infrared

The temperature dependence of the bending ν₂, combination ν₂ + ν _L , and stretching (ν₁, ν₃, 2ν₂) absorption bands in the infrared spectra of supercooled water with a temperature-change step Δt from 2 to 2.5°C was studied using an advanced infrared Fourier spectrometer. It was found that the frequency of the maximum of the stretching absorption band (2700–3700 cm^?1) decreases with the reduction of the water temperature from ?0.5 to ?5.0°C. The frequency of the maximum of the combination absorption band (2130 cm^?1) increases with the reduction of the water temperature in a range from ?3.0 to ?5.0°C. The frequency of the maximum of the absorption band of bending oscillation (1640 cm^?1) is invariable with a reduction of the water temperature from ?0.5 to ?5.0°C.     

Isotopic shifts and the hyperfine structure of the samarium spectral lines at 672 and 686 nm

Spectra of saturated absorption of Sm atomic vapor from the ground state ⁷ F ₀ and the first even metastable level ⁷ F ₁, ε′=292.58 cm^?1 of the 4f ⁶6s ² configuration to the odd level 4_f ⁶(⁷ F)6s6p(³ P ^o)⁹ F ₁ ^o , ε,=14863.85 cm^?1 were recorded. The lines of the isotopic series were identified, and the hyperfine structure of lines in the spectra of isotopes with a nonzero nuclear spin was determined. The relative isotopic shifts and the hyperfine splitting of the even level 4f ⁶6s ²(⁷ F ₁) were determined.