The first s-Rydberg transitions of ethyl bromide and ethyl iodide as related to the corresponding methyl halides

The transitions observed in the first s-Rydberg region of the spectra of ethyl bromide, ethyl bromide-d₅, and ethyl iodide are reported and assigned. The assignments are made by examining the effect of symmetry reduction from C_3v to C_s on the observed electronic states and vibrational modes of the corresponding methyl halide spectrum. The calculated spectra obtained in this way give good agreement with the observed spectra. These resulting assignments are discussed in terms of a competition between spin-orbit coupling and hyper-conjugation.     

Complex polar Kerr effect spectra of magnetoplumbite

The paper presents the complex polar Kerr effect spectra in hexagonal ferrite PbFe₁₂O₁₉ (magnetoplumbite) at 290 K between 2 and 5·5 eV. The spectra are compared with the corresponding spectra in Li_0.5Fe_2.5O₄. The previously published data on optical constants of magnetoplumbite are employed to obtain the off-diagonal permittivity tensor element spectra. The effect of nonzero angle of incidence in uniaxial magnetic crystals on the observed polar Kerr effect is briefly discussed.     

Comparative mössbauer and TDPAC studies on the after-effects of the ec decays of119Sb and111In in α-Fe2O3

Mössbauer emission spectra of (¹¹⁹Sb→)¹¹⁹Sn and TDPAC spectra of (¹¹¹In→)¹¹¹Cd in α-Fe₂O₃ are measured. The origin of apparetly much pronouced after-effects of the EC decay observed in the TDPAC spectra, as compared with those in the Mössbauer spectra is clarified.     

Infrared reflection absorption spectra of Fe(CO)5 adsorbed on Au surfaces

Infrared reflection absorption spectroscopy (IRAS) shows that the CO stretching bands of Fe(CO)₅ adsorbed on Au surfaces are significantly different in band shape as well as in frequency from the bands observed in a transmission mode. This difference has been observed for other metal substrates and explained in terms of the anomalous dispersion of the refractive index in the region of the observed bands. The refractive indices of Fe(CO)₅ are calculated using the Kramers-Kronig relation from the transmission spectra of Fe(CO)₅ adsorbed on a sapphire plate, an SiO₂-coated sapphire plate, and an Au film evaporated on a sapphire plate, and the IRA spectra of Fe(CO)₅ adsorbed on Au are calculated using Fresnel's formula. The results show that the ν₁₀ band of Fe(CO)₅ becomes very sharp and shifts to higher frequencies by more than 10 cm⁻¹, while the ν₆ band becomes a shoulder of the v₁₀ band, in good agreement with the observed IRA spectra. The IRAS calculation also shows that the weak band observed at 2114 cm⁻¹ for the Au film remains unchanged in position, in agreement with the observed IRAS.     

Effects of optical activity on exciton luminescence of CdS

The luminescence spectra have been investigated in the vicinity of the B_n=1 exciton resonance in CdS at T = 2 K. The effect of “weak” optical activity on luminescence has been observed for the first time. The observed spectra are compared with the frequency dependences of the polariton transmission coefficients.     

Temperature dependent study of the single crystal electronic spectrum of octahedral Ni2+ ion subjected to distortions in weak fields

Electronic spectra of two high spind ⁸ nickel complexes, Ni(en)₃Cl₂.2H₂O and Ni(OAc)₂.4H₂O, are reported. Polarized spectra were measured at 298 K. Temperature dependent spectra were measured using unpolarized light down to 20 K. The spectra at 20 K are well resolved revealing the features of spin-forbidden transitions and vibrational fine structure on some of the bands. Some of the spectra are deconvoluted to separate out the overlapping bands. The assignments are made usingD ₃ symmetry for Ni(en)₃Cl₂.2H₂O complex whileD ₄ symmetry is used for Ni(OAc)₂.4H₂O. The energies of the spectroscopic states are calculated and compared with the observed transition energies. The distortion parameters are determined.     

A Raman spectroscopic study of the uranyl carbonate rutherfordine

The molecular structure of the uranyl mineral rutherfordine has been investigated by the measurement of its Raman spectra at 298 and 77 K and complemented with infrared spectra. The infrared spectra of the (CO₃)²⁻ units in the anti‐symmetric stretching region show complexity with three sets of carbonate bands observed. This, combined with the observation of multiple bands in the (CO₃)²⁻ bending region in both Raman and IR spectra, suggests that both monodentate and bidentate (CO₃)²⁻ units are present in the structure in accordance with the X‐ray crystallographic studies. Complexity is also observed in the IR spectra of (UO₂)²⁺ anti‐symmetric stretching region and is attributed to non‐identical UO bonds. Both Raman and infrared spectra of the rutherfordine show the presence of both water and hydroxyl units in the structure, as evidenced by IR bands at 3562 and 3465 cm⁻¹ (OH) and 3343, 3185 and 2980 cm⁻¹ (H₂O). Raman spectra show the presence of four sharp bands at 3511, 3460, 3329 and 3151 cm⁻¹. Copyright © 2007 John Wiley & Sons, Ltd.     

X-ray and UV photoelectron spectra of the metal sesquioxides

He(I,II) and MgKα valence region photoelectron spectra of polycrystalline Ti₂O₃, V₂O₃, Cr₂O₃, Mn₂O₃, Fe₂O₃ and Rh₂O₃ have been recorded. The method of sample preparation employed gave rise to UV-PE spectra which are significantly different from those previously reported. While clear changes are observed in the spectra accompanying the semiconductor-to-metal transition of V₂O₃ at 150 K, there is no apparent modification of the Ti₂O₃ spectra accompanying its second order transition at 500 K. The remaining first row transition metal sesquioxides exhibit spectra indicative of localised 3d electrons.     

Luminescence study of cerium-doped La2Hf2O7: Effects due to trivalent and tetravalent cerium and oxygen vacancies

X-ray excited emission spectra, photoluminescence excitation and emission spectra, optical reflectivity spectra, and pulsed X-ray and optical excited luminescence decay measurements are reported for cerium-doped La₂Hf₂O₇ powders prepared by solid state synthesis. A broad luminescence associated with oxygen vacancies is observed in the region 350–750 nm with a peak around 460 nm. The photoluminescence spectra and the number of oxygen vacancies vary for samples annealed in oxidizing or reducing atmospheres and with the temperature of the synthesis process. Increasing the cerium concentration reduces the oxygen-vacancy-related emission due to the presence of Ce⁴⁺. First principles calculations predict that Ce⁴⁺ can substitute in Hf sites; this is confirmed from the optical reflectivity spectrum of cerium-doped La₂Hf₂O₇. Photoluminescence excitation and emission spectra characteristic of Ce⁴⁺ charge transfer transitions and possibly Ce³⁺ are also observed. Although trivalent cerium may be present, no emission observed from cerium-doped La₂Hf₂O₇ can be attributed to Ce³⁺ in La sites.     

The results of disorder on the empty states in GeTe as seen by x-ray absorption

The Te L₁ and L₃ X-ray absorption spectra for GeTe in amorphous and crystalline form are presented. The spectra have been unfolded for the broadening effects of the inner levels employed. Significant effects of disorder are observed and are assigned to changes in the empty d-states, while the states with p-symmetry appear to be unaffected.     

Fundamental absorption spectra of solid hydrogen

Absorption spectra of solid H₂ and D₂ are measured in the range 10–40 eV at 2K for the first time, using synchrotron radiation. The spectra can be divided into two components; exciton and interband transitions. The exciton absorption consists of bands corresponding to molecular transitions, and vibrational structures are observed in the first exciton band of solid H₂.     

Plasmaresonanzemission und Plasmaresonanzabsorption an dünnen Kaliumschichten

Optical transmission and emission spectra in the region of the plasma frequencyω _p were measured on thin potassium films evaporated on sapphire substrates of various temperatures. For the foils condensed at a temperatures of the substrateT _a T _a >?165 °C transmission spectra were observed which transmission minima are displaced to frequencies less thanω _p . Plasma resonance emission was observed from these foils. Comparison with calculated emission spectra gives an approximate agreement.     

Raman scattering in the Bi2TeO5 single crystal

Polarized Raman spectra of the Bi₂TeO₅ single crystal have been investigated for the first time. The group-theoretic analysis of the first-order vibrational spectra is performed. The number of the experimentally observed bands is less than the predicted number of normal modes. The spectral ranges with similar bands are revealed. Some ranges in the spectra of Bi₂TeO₅ are identified from the spectral data for the materials containing bismuth-oxygen and tellurium-oxygen complexes.     

Angle-resolved photoemission study of a vacancy-induced state in substoichiometric VC

A vacancy induced state has been identified at about 1.8eV binding energy on the (100) face of VC_0.80 using angle-resolved photoelectron spectroscopy. The recorded spectra are compared with calculated spectra for VC_1.0 and the results show that the origin of the observed state cannot be accounted for by the energy band structure of VC_1.0. Photoemission spectra recorded after exposing the clean surface to O₂ and CO are also presented and used in a discussion of the sensitivity of the vacancy induced state to surface contamination.     

Theory of two-phonon absorption processes in liquid paraffins

Calculated absorption spectra are given for linear C₈H₁₈, C₁₀H₂₂, C₁₆H₃₄ and C₂₀H₄₂ chains, based on the assumption of a two-phonon absorption mechanism. In the present work the normal modes of vibration of different finite chains are computed directly, without recourse to the Pitzer sampling approximation and without the assumption of strict k-selection rules. The calculated spectra are found to be much more sensitive to chain length than the experimental spectra. A possible explanation of the relative insensitivity of the observed spectra is suggested in terms of a characteristic chain segment length common to all the chains. Ironically, the apparent importance of chain segmentation in the two-phonon absorption suggests that one-phonon transitions may also play a significant rôle in the absorption process.     

Optical spectra and energy band structure of AgAsS2 crystals

Ground and excited states of three exciton series are observed in the region of fundamental absorption edge of AgAsS₂ crystals. The contours of exciton reflection spectra are calculated and the main parameters of excitons and energy bands are determined in the center of Brillouin zone. The optical reflection spectra are investigated at 30 K in E∥c and E⊥c polarizations in AgAsS₂ crystals in the region of 2-6 eV. The optical functions are calculated from the reflection spectra and a scheme of electronic transitions responsible for peculiarities of reflection spectra deep into the absorption band is proposed.     

FeCrB非晶合金带铁磁共振研究

本文报道用电子自旋共振谱仪所测得的FeCrB非晶合金带的铁磁共振谱,给出了谱形随温度变化的实验结果。用“独立晶粒近似”理论解释了样品中的磁相变化,并讨论了线宽△H随温度T的变化。为研究非晶合金带材料的性能提供了新的实验结果。 关键词：     

Infrared absorption spectra of 2,3- and 3,5-dichloroaniline

The infrared absorption spectra of 2,3- and 3,5-dichloroanilines have been recorded in the region 250–4000 cm⁻¹. The spectra of the latter are recorded in solid phase (KBr and Nujol mull) and in CS₂/CCl₄ and CHCl₃ solutions while that of the former in thin film only. The spectra have been analysed assuming C ₃ and C_2v point group symmetry respectively and a tentative assignment of the observed bands to different fundamental modes has been made.     

Study of L2,3M4,5M4,5 Auger spectra of Zn and Cu in molecular ZnCl2 and (CuCl)3 vapours

L_2,3M_4,5M_4,5 Auger electron spectra of Zn and Cu have been measured in molecular ZnCl₂ and (CuCl) ₃ vapours. The spectra have been analyzed and compared with the corresponding free-atom spectra. It is found that the main features of the spectra are atomic-like. The energies are shifted by 0.55 eV in ZnCl₂ and by 3.2 eV in (CuCl)₃ towards higher kinetic energy compared with the corresponding free-atom spectra. For the intensity ratios between the L₃ and L₂ groups, the values 2.8 and 3.7 are obtained for Zn and Cu, respectively. These intensity ratio, together with energy considerations based on free-atom Dirac—Fock calculations and observed Auger shifts, indicate that the L₂L₃M_4,5 Coster—Kronig process is energetically possible in (CuCl)₃ molecular clusters but not in ZnCl₂. The satellite structure in the spectra studied also supports this conclusion.     

Raman spectra of crystalline double sulphates Part II. Ammonium double sulphates

Raman spectra of single crystals of (NH₄)₂M(SO₄)₂·6 H₂O whereM=Mg, Zn Ni or Co have been recorded using λ 2537 excitation. Interesting results concerning the substitution of the divalent atoms in the double sulphate lattice on the sulphate and ammonium frequencies are observed. The spectra of these double sulphates are discussed in the light of the known crystal structure details and in relation, to the spectra of the corresponding potassium double sulphates, reported recently by the author. The Raman spectrum of NaNH₄SO₄·2 H₂O has also been recorded for the first time and the results obtained are also included.