Rydberg transitions of aniline and N,N-diethylaniline

The absorption spectra of aniline and N,N-diethylaniline in the gaseous and condensed phases were measured in the 30 000–60 000 cm^?1 region. The magnetic circular dichroism (MCD) spectra of these compounds in the gas phase and in solution were also measured in the region 30 000–49 000 cm^?1. The MCD signals due to the Rydberg transitions were newly observed for N,N-diethylaniline. On the basis of these data, we demonstrated that in the region below 50 000 cm^?1 the Rydberg transition bands appear at 47 180 cm^?1 for aniline and at 36 520, 38 880, and 42 000 cm^?1 for N,N-diethylaniline. Besides these, in the region higher than 50 000 cm^?1, a number of Rydberg transition bands were observed for both compounds in the gaseous state. The observed Rydberg transition bands were analyzed with the aid of the Rydberg formula: they were assigned for aniline to the np- and nd-type series converging to the first and second ionization potentials, and for N,N-diethylaniline to the us- and two np-type series converging to the first ionization potential.     

Magnetic circular and linear dichroism of iron garnets thin films

Low temperature absorption, MCD and MLD spectra are reported for pure and substituted Y₃Fe₅O₁₂ thin films in the 13000–33000 cm^?1 spectral range. The materials were obtained by liquid phase epitaxial growth on a Gd₃Ga₅O₁₂ substrate. Above 19000 cm^?1 we demonstrate that our transmission experiments on garnet films provide the same information as do reflexion measurements on bulk crystals. Below 19000 cm^?1 however, the former are much more reliable and accurate. All our data indicate that the films are of excellent optical quality. MCD and MLD spectra show a considerably increased resolution as compared to the absorption spectrum and help in sorting out most of its numerous overlapping components. Finally we prove unambiguously that Clogston's theoretical interpretation is qualitatively correct in the 13000–23000 cm^?1 region and even probably at higher wavenumbers.     

3-Naphthyl-4-Quinazolone Infrared and Nuclear Magnetic Resonance Band Assignments

Abstract

The ir and nmr spectra of 24 3-naphthyl-4-quinazolones were examined. There are three principal ir bands in the 1500 and 1705 cm^?1 region of the spectra. The first at 1685–1705 cm^?1 is assigned to the tertiary amide carbonyl (ArCONR₂), the second at 1593–1645 cm^?1 to the anil chromophore (ArN=C-N) and the third to the naphthalene ring at 1600 cm^?1. The nmr band assignments are straight forward.     

Magnetic circular dichroism of CdTe nanoparticles

Magnetic circular dichroism (MCD) of water-soluble CdTe nanoparticles was observed in the visible spectral range for the first time. Diameter of nanoparticles varied from 2.3 to 4.5 nm. Absorption and photoluminescence spectra were also recorded. Absorption line at 19400 cm^?1 and luminescent line at 18200 cm^?1 were observed. Splitting of value 960 cm^?1 was revealed in the MCD spectrum. Approximately the same splitting was extracted from the absorption spectrum. The MCD was identified as the temperature independent paramagnetic mixing effect. Nature of the absorption line and of its splitting are discussed.     

Laser excited luminescence spectra of zirconia

Luminescence spectra of ivory zirconia (Zr0₂) excited by an argon-ion laser (19,436–21,839 cm^?1) reveal a complex pattern consisting of both sharp and diffuse peaks in the 16,000–19,000 cm^?1 region. The intensity behavior of these features depends markedly on the excitation frequency. The sharp luminescence peaks of the 18,140–18,600 cm^?1 region are attributed to phonon-mediated de-excitation of excited states of the impuriity-doped ZrO₂ lattice. The more diffuse luminescence bands of the 17,700–18,000cm^?1 region may be associated with the electron traps observed in glow experiments and/or with higher-order phonon processes.     

Infrared Spectra of Poly(Ethylene Terephthalate) γ-Irradiated in Organic Solvents

The infrared spectra of poly(ethylene terephthalate) γ-irradiated in presence of organic solvents were recorded over the spectral region 200–300 cm^?1. The analysis of these spectra showed that the combined effect of solvent and γ-irradiation results in appearance of two strong bands at 1550 and 1630 cm^?1, increase in the intensities of the gauche bands at 1450 and 1370 cm^?1 and decrease in the intensity of the trans-band at 1340 cm^?1. The aromatic ring C=C stretching band at 1410 cm^?1 was also affected. The profound spectral changes were observed only in samples irradiated in presence of solvents and were not observed in samples treated with solvents or only irradiated in atmosphere of air, these spectral changes were attributed to the changes in the intermolecular of intramolecular forces as a result of penetration of solvent molecules in the polymer and the ionizing effect of γ-iffadiation. It was found that the extent of the intensity variations depends on the nature of the solvent.     

Structure comparison of Orpiment and Realgar by Raman spectroscopy

Raman spectroscopy was used to characterize and differentiate the two minerals, Orpiment and Realgar, and the bands related to the mineral structure. The Raman spectra of these two minerals are divided into three sections: (a) 100–250?cm^?1 region attributed to the sulfur–arsenic–sulfur bending vibrational modes; (b) 250–450?cm^?1 region due to the arsenic–sulfur stretching vibration; and (c) 450–850?cm^?1 region assigned to overtone and combination bands. A total of 14 Raman bands for the spectrum in the 1600–100?cm^?1 region were observed. The significant differences between the minerals Orpiment and Realgar are observed by Raman spectroscopy. Realgar shows the typical bands observed at 340, 268, 228, and 218?cm^?1, and the special bands at 379, 289, 200, 176, and 102?cm^?1 for Orpiment are observed. The additional bands in 850–450?cm^?1 region are only observed for the mineral Orpiment, which may be attributed to overtone and combination bands in the Raman spectrum. The variation in band positions is dependent upon the structural symmetry, arsenic–sulfur bond distances, and angles. Moreover, another cause for the difference is the effect of the intermolecular forces and to the strong coupling between close lying external and internal modes. The difference of these two minerals structure induce tremendous diversity on Raman spectra, so Raman spectroscopy offers the information on the molecular structure of the minerals Orpiment and Realgar.     

Temperature Effect on the IR Absorption Spectra of Hydrogen Bonded (N[sbnd]…N)+ Homoconjugated Cations

Abstract

The effect of temperature on the absorption spectra from 50 to 3200 cm^?1 of a number of amine semiperchlorates and perchlorates of amines with two basic centres in which the hydrogen bridges (N [sbnd] H…N)⁺ are formed, was investigated. Three broad absorption regions may be distinguished in the spectrum, viz., between 100 and 900 cm^?1, 600 and 1800 cm^?1 and 1700 and 2900 cm^?1. The latter one may be assigned to the stretching vibration ν_S (N [sbnd] H…N).

A shift of this band peak (which is usually a doublet at room temperature for aromatic amines) towards longer wavelengths on decreasing the temperature may be an evidence that the bridge becomes shorter. Simultaneously with these changes, most salts under investigation exhibit a strong increase in low-frequency absorption intensity at about 400–600 cm^?1. It may be suggested that this absorption results from a transition between the split levels of the zero vibrational state.     

Infrared Spectra of Morfolonium (mpH)2Mo2Cl6(H20)2(I),(mpH)2Mo2ClxBr6-x(H2O)2(II)/ (mpH)2Mo2Br6(H2O)2(III) and the Pyridinium (PyH)2Mo2I6(H2O)2(IV)Hexahalo-di(aquo): dimolybdate(II) Complexes,Containing Quadruple Metal-Metal Bounds

Abstract

The electronic (800–400 nm), infrared (4000–200,400–20 cm^?1), ordinary Raman (400–200 cm^?1) spectra of morpholinium and the pyridium hexahalo-di(aquo) dimolybdate(II) complexes, containing quadruple metal-metal bonds were investigated. The electronic spectra of the solid compounds at various temperatures (25,100 and 300K) demonstrate intense and structured bands in the visible region (510–582 nm) attributed to the expected δ→δ? transitions.

From the infrared and Raman spectra, the skeletal stretching modes in these complexes have been localized, and the charectenstic bands of these ions were observed in the expected regions.

Finally, the ionic interections were relatively weak, but the existance of phenomena was perceptible and the result was obtained in agreement with X-ray data.     

Effect of pressure on the intensity of absorption bands in the IR spectra of compacted polyethylene powde

The investigation of the IR spectra of compacted reactor powders of ultra-high-molecular-weight polyethylene showed that the intensities of the absorption bands depend on the compaction pressure; namely, they decrease with increasing pressure. It is found that the ultimate pressure above which the absorption band intensity ceases to decrease depends on the spectral position of the band; the shorter the wavelength, the higher the ultimate pressure. This pressure is 5–10 MPa for bands in the long-wavelength spectral region (the band at 720 cm^?1) and 100 MPa for the short-wavelength region (the band at 5875 cm^?1). It is assumed that this phenomenon is related to a change in the size of pores d with pressing. Beams with wavelengths λ < d will undergo multiple diffuse reflections and reach a photodetector that is weaker than beams with λ > d. With increasing pressure, the size of pores decreases and the boundary between the two regions of the spectra shifts to short wavelengths.     

The absorption spectrum of 12C2H2 IV. The regions 7600–9200 cm−1 and 10600–11500 cm−1

The absorption spectrum of ¹²C₂H₂ has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10600–11 500 cm^?1 spectral region, where no absorption bands were previously reported. Fifteen bands starting from the vibrational ground state are observed and rotationally analysed. All corresponding excited vibrational levels were assigned using the polyad model, the so-called cluster model (El Idrissi, M.I., Liévin, J., Campargue, A., and Herman, M., 1999, J. chem. Phys., 110, 2074) which allows vibrational energies, rotational B_v constants and, to some respect, relative band intensities to be predicted. Additional data and constants are also provided in the range 7600–9200cm^?1, whenever improving the literature results, from spectra recorded previously at ULB using Fourier transform spectroscopy. The assignment procedure in the range recorded by ICLAS is detailed, leading to a deeper understanding of vibration-rotation and intensity features of the absorption bands within the frame of the cluster model.     

Indole in Argon Matrix: The Near UV Spectra.

Abstract

The near UV absorption, steady-state polarized fluorescence excitation and time–-resolved fluorescence emission spectra of indole in argon matrix are reported. The absorption maxima of the four lowest singlet transitions were identified at 35095 cm^?1(also the S_{1, 0} 0–0 band), 37650 cm^?1 (S_2,0), 47415 cm^?1 (S_3,0), and 51680 cm^?1 (S_4,0). No distinct 0–0 band of the second transition was identified but the linearly polarized, steady-state fluorescence excitation spectrum indicates an onset of weak S_2,0 bands on the blue side of the S_1,0 0–0 peak (35095 + 400 cm^?1). Only one fluorescence emission component, of 4.9±0.2 ns, was obtained by excitation over the S_{1, 0} 0–0 + 565 cm^?1 to S_1,0 0–0 - 245 cm^?1 domain. The reported data strongly suggest the ¹L_b ^?1A₁ and ¹L_a ^?1A₁assignment for the lowest and next lowest transitions, respectively.     

The Electronic Absorption Spectrum of Hafnium Monochloride

Abstract

Intracavity laser spectroscopy has been applied for investigation of absorption spectrum of HfCl molecule. In the region 560–700 nm 59 bands have been obtained. Rotational structure analysis of 0–0 band indicated that Hund's case (c) of angular moment coupling applied to this molecule. The molecular constants (cm^?1) calculated for upper and ground electronic states are: ω′ = 353.05 cm^?1, ω″ = 379.65 cm^?1, B′=0.21486 cm^?1 B″ = 0.21801 cm^?1.     

Hydrogen-bonded OH and OD overtone bands and potential energy curve of methanol

The absorption spectra of CH₃OH, CH₃OD, CD₃OH, and CD₃OD as pure liquids and as carbon tetrachloride solutions were measured in the 3,850 – 16,600cm^?1 region. In addition to the various combination bands, the higher overtone bands of the hydrogen-bonded OH stretching vibration of self-associated methanols were observed at ～6470, 9300–9700, and 12,200 – 12,700 cm^?1 with broad half-widths of ～700, ～1200, and ～1800 cm^?1, respectively, and those of the OD stretching vibration, at ～4900, 7200–7400, and 9200–9600 cm^?1 with half-widths of ～370, ～700, and ～1200 cm^?1, respectively. With the aid of the observed frequencies, we determined the single minimum potential energy curve for the hydrogen-bonded OH and OD stretching vibrations of self-associated methanols. Furthermore, the absorption band due to double excitation of two neighboring OH groups linked together by a hydrogen bond was quantitatively analyzed by using the isotopic isolation technique. The double excitation band of CH₃OH as pure liquid was found to appear at 6730 cm^?1 with an absorbance of 0.08 at 1 mm light path length.     

Silicon negative ion implantation induced vacancy defects in thermally grown SiO2 thin films

ABSTRACT

Thermally grown SiO₂ thin films on a silicon substrate implanted with 100?keV silicon negative ions with fluences varying from 1?×?10¹⁵ to 2?×?10¹⁷ ions cm^?2 have been investigated using Electron spin resonance, Fourier transforms infrared and Photoluminescence techniques. ESR studies revealed the presence of non-bridging oxygen hole centers, E′-centers and P_b-centers at g-values 2.0087, 2.0052 and 2.0010, respectively. These vacancy defects were found to increase with respect to ion fluence. FTIR spectra showed rocking vibration mode, stretching mode, bending vibration mode, and asymmetrical stretching absorption bands at 460, 614, 800 and 1080?cm^?1, respectively. The concentrations of Si–O and Si–Si bonds estimated from the absorption spectra were found to vary between 11.95?×?10²¹ cm^?3 and 5.20?×?10²¹ cm^?3 and between 5.90?×?10²¹ cm^?3 and 3.90?×?10²¹ cm^?3, respectively with an increase in the ion fluence. PL studies revealed the presence of vacancies related to non-bridging oxygen hole centers, which caused the light emission at a wavelength of 720?nm.     

Unusual Bands in the Infrared Spectra of Some Chars

Abstract

When organic materials are charred at low or medium temperatures (up to about 450–500°C), their infrared (IR) spectra show a plethora of bands below about 2000 cm^?1, and there are additional bands in the OH and CH stretching regions, above about 2600 cm^?1. The in-between region, from about 2600 to 200 cm^?1, is quite “empty” (except for an occasional atmospheric CO₂ band caused by instrument imbalance). The reason for this emptiness is, simply, that there are very few species that have fundamentals in that region, as is well known from group frequency tables; and those that do absorb, such as metal hydrides, are quite unlikely to exist in organic precursors. Some overtones or combinations may appear, but these are usually very weak. We have, however, observed some bands in the empty region on several occasions.     

New Identification Bands in the Infrared Spectra Of 1- and 2-Substituted Benzotriazoles

Abstract

Some new identification bands characteristic of 1- and 2-substituted benzotriazole derivatives have been found in their infrared spectra. The skeletal in- plane rings vibration near 1490 cm^?1 and some bands in the 795-760 cm^?1 region have been typical for 1-substituted compounds whereas the vibrations at 875-820 cm^?1 have been observed as characteristic of a quinoid system of 2-substituted benzotriazoles. New characteristic bards examination allows to identify better both isnmers.     

Hard mode infrared spectroscopy of CaTiO3—CaFeO2.5 perovskites

Abstract

Powder-absorption infrared (IR) spectra of perovskites CaFe_xTi_1?x O_3?x/2 (0≤x≤1) annealed at different temperatures were investigated at room temperature in the range 135–2000 cm^?1. The spectra change as a function of composition, annealing temperature and structural state (order-disorder of oxygen vacancies). Autocorrelation analysis has been used to determine variations of average line widths of groups of peaks in the primary IR spectra. The band widths increase on increasing Fe content in the region of the structures with disordered oxygen vacancies and they decrease on going through the order-disorder boundary. High degrees of local structural heterogeneity are suggested by the effective line widths of the phases at intermediate compositions. The intensity of bands at ～150 and ～443 cm^?1 decreases with increasing Fe content in the compositional range of the disordered structures. Finally, for every annealing temperature, the frequency of the band at ～600cm^?1 systematically shifts to higher values on increasing Fe content, these values decreasing again for the fully ordered structures.     

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.     

The Translation Mechanism of Smectite to Illite: An Infrared Spectroscopic Study of Ordered Mixed-Layer Illite/Smecite

The infrared spectral characteristics of ordered mixed-layer illite/smectite interstratified clay mineral with different mixed-layer ratios (S% = 5%, 10%, 15%, 20%, 25%, and 30%, where S% is mixed-layer ratio) from the Shihezi Formation of Late Permian in the Hanxing mining area, Hebei province of China, were studied by infrared spectroscopy. The results show that three infrared regions (3625 cm^?1±, 1200–1000 cm^?1, 850–700 cm^?1) changed with S%'s variation. The characteristic absorption bands of smectite at 3640 cm^?1, 1030 cm^?1, and 825 cm^?1 disappeared gradually with the decrease of S%, and the intensity of characteristic absorption bands of illite at 3625 cm^?1, 1100 cm^?1, 1024 cm^?1, 796 cm^?1, and 777 cm^?1 increased. These changes indicated that the illitization of smectite was realized by partial substitution of aluminum iron (Al³⁺) for silicon iron (Si⁴⁺) in silico-oxygen (Si–O) tetrahedron.