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.     

Subterahertz electrodynamics of (TMTSF)2X (X = ClO4, PF6) salts

The terahertz-subterahertz spectra of the complex permittivity and dynamic conductivity of polycrystalline (TMTSF)₂ClO₄ and (TMTSF)₂PF₆ samples are measured quantitatively. The spectra of (TMTSF)₂ClO₄ have absorption lines at frequencies of 7 and 30 cm^?1. The obtained temperature dependences of the line parameters in the range 5–300 K cast some doubt on the earlier concept of their phonon origin. An excitation is detected at temperatures below 20 K in the frequency range near 30 cm^?1, and its nature is related to the activation of a transverse acoustic phonon caused by the folding of the Brillouin zone due to the ordering of noncentrosymmetrical anions below 20 K. An increase in the carrier relaxation rate is found in this temperature range, which indicates a close relation between the electron and phonon subsystems in (TMTSF)₂ClO₄. Sings of additional low-energy excitations that should manifest themselves at frequencies below 1–2 cm^?1 are detected. (TMTSF)₂PF₆ containing centrosymmetrical anions has no absorption lines in the frequency range 3–20 cm^?1 and the temperature range 5–300 K.     

Electronic spectra and electronic structures of [2.2]paracyclophane and related compounds

The absorption spectra of [2.2]paracyclophane (PC), tetramethyl [2.2]paracyclophane (DD), and triple- and quadrupole-layered cyclophanes (DDD and DDDD) were measured with the n-heptane and 3-methylpentane solutions in the range of 25000–59000 cm^?1. The polarized absorption spectra of the [2.2]paracyclophane single crystal were measured in the range of 30000–50000 cm^?1 for the ab plane and 30000–37500 cm^?1 for the ac plane. Strong bands corresponding to the 180 nm band of benzene were newly observed at 53000, 49750, 49600, and 50000 cm^?1 for PC, DD, DDD, and DDDD, respectively.The electronic structures of PC, DD, DDD, and DDDD were studied semiempirically by considering the configuration interaction among the ground, locally excited and charge-transfer configurations.From the band positions, the absorption intensities, and the band polarization obtained experimentally and theoretically, we made the more reasonable and more reliable band assignments compared with those by the previous authors.     

Rydberg series of NO converging to the ionic states b3Π, A1Π, and w3Δ

Rydberg series of NO in the 600–1000-Åregion were investigated by using a 6.65-m high-dispersion vacuum spectrograph. The previous β, γ (v = 0), and γ (v = 1) Rydberg series were extended up to n = 31, 31, and 28, respectively. From the analysis of these Rydberg series, accurate ionization energies were obtained: 133 565 ± 3 (16.5596 eV) for b³Π (v = 0); 147 811 ± 3 (18.3258 eV) for A¹Π (v = 0); 149 372 ± 3 cm^?1 (18.5193 eV) for A¹Π (v = 1) of NO⁺. A new Rydberg series converging to one of the triplet components in b³Π was identified, and the coupling constant of b³Π was estimated to be 35 ± 8 cm^?1. Higher members of two Rydberg series were newly observed in the 700–725-Åregion. From their series limits, 139 926 ± 3 and 141 160 ± 3 cm^?1, they were assigned to be the Rydberg series converging to the v = 3 and 4 levels of ω ³Δ in NO⁺.     

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.     

Vacuum ultraviolet absorption spectra of dichlorosilane,dichloromethylsilane and dichlorodimethylsilane

The vapor phase vacuum ultraviolet absorption spectra of dichlorosilane, dichloromethylsilane and dichlorodimethylsilane are reported for the region from 40 000 to 83 000 cm^?1 (250-120 nm). Absorptions of these compounds are assigned as primarily Rydberg excitations of chlorine valence non-bonded electrons. The σ* ← np(SiCl) transition for these compounds is the first observed absorption and is badly overlapped with the first Rydberg absorptions. The first three ionization potentials of dichloromethylsilane were calculated to be 11.47, 11.82, and 12.28 eV using averaged term values and transition energies. The analysis of these spectra revealed that the first p and d molecular Rydberg states appear to be nearly degenerate and that these Rydberg levels are greatly destabilized with methyl substitution. The results of this study support the presence of strong d-p(SiCl) interactions. The strength of this effect is compared in dichlorosilane and dichlorodimethylsilane using an empirical relation.     

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.     

The polarized reflection and absorption spectra of perylene crystals in monomeric and dimeric forms

The electronic absorption spectra of perylene crystals in the α- and β-forms were measured by the normal incidence reflection method in the spectral region from 20 000 to 60 000 cm^?1. From the absorption spectrum polarized perpendicular to [1$\text{1}$0] axis of the α-form crystal, the bands around 24 000 cm^?1 were determined to be polarized along the long molecular axis. Two strong bands with different polarizations were observed around 50 000 cm^?1 for each of the α- and β-perylene crystals and were assigned to the transitions to the ¹B_2u and ¹B_3u states. The observed polarized absorption spectra as a whole were consistent with the theoretical results by Hummel and Ruedenberg and the reflection method was found to be suitable to the polarized absorption measurement of strong bands of crystals. The observed factor-group splittings were compared with the theoretical values, the oriented gas model being found to be applicable to the β-form crystal.     

Inner shell electron energy loss spectra of the methyl amines and ammonia

Electron energy loss Spectroscopy has been used to obtain the inner shell excitation spectra of the methyl amines CH₃NH₂, (CH₃)₂NH and (CH₃)₃N for both the N 1s and C 1s regions. A spectrum of the N 1s region of NH₃ is also presented at higher resolution than previously published data. The C ls spectra are all very similar and the discrete portions may be assigned to Rydberg transitions. However, features attributable to a σ^* shape resonance are observed just above the N 1s and C ls ionization edges. The NH₃ spectrum is ascribed to Rydberg transitions. The N 1s spectra of the methyl amines, however, become increasingly dominated by a σ* resonance in the continuum with increased methylation. The features in the inner-shell spectra are compared with the reported valence-shell optical absorption spectra and support the Rydberg assignment. The inner-shell spectra of (CH₃)₃N and NH₃ are also compared with previously published inner shell electron energy loss spectra of NF₃ and the third row phosphorus analogues PF₃,P(CH₃)₃andPH₃.     

Far infrared optical properties of free carriers in GaAs

Transmission and reflection measurements over the frequency range 17–200 cm^?1 were made on GaAs with electron concentrations of 1·0 and 4·9 × 10¹⁶ cm^?3. The plasma frequencies of the samples fall within the measurement range. When values of the free carrier absorption coefficient α and the real refractive index n as derived from the data are plotted in the form (αn)^?1 vs (frequency)², the plots are linear, in excellent agreement with Drude theory. Deduced values of effective mass, relaxation time and mobility agree with published values and with a d.c. drift measurement.     

IR spectra of the optical constants of an industrial high-pressure polyethylene film

The IR spectra of the real n(ν) and imaginary κ(ν) parts of the complex refractive index of an industrial high-pressure polyethylene film are measured by the methods of transmission and attenuated total reflectance spectroscopy in the range 700–750 cm^?1 taking into account the anisotropy and the structural inhomogeneity of the film over its thickness. It is proposed to use these spectra as the reference spectra for polyethylene films in the range around 720 cm^?1.     

Infrared Study of Solid Cycloheptanol

Abstract

Infrared absorption spectra of cycloheptanol-OH have been measured in the 50–3700 cm^?1 frequency range for crystal II', II, I and liquid phases. Order-disorder behaviour concerning orientational, conformational and hydrogen-bond properties is discussed.     

Pressure dependence of the absorption edge at the E0 gap of mocvd - Grown ZnTe films

Abstract

We have investigated the direct gap absorption of 1μm thick ZnTe-epilayers grown on GaAs substrates by metalorganic chemical vapour deposition (MOCVD). Free ZnTe-layers were obtained by selective etching. The absorption coefficient was measured up to about 50000 cm^?1 in a diamand anvil cell in the temperature range from 115–300 K. The spectra near the direct gap E₀ are dominated by a sharp excitonic structure. Its change with pressure is evaluated by a model which allows to determine the pressure shift of the gap energy dE₀/dP and the change of the Rydberg energies of the excitons dR*/dP.^[1]     

Photo-absorption studies on carbonyl sulphide in 30,000–91,000 cm−1 region using synchrotron radiation

Photo-absorption spectrum of carbonyl sulphide (OCS) is recorded in 30,000–91,000 cm^?1 (3300–1050 Å) region at an average resolution of 1.2 Å using Photo-physics beamline on the 450 MeV Indus-1 synchrotron radiation source at RRCAT Indore, India. Owing to significant absorption cross section dependence, spectra of OCS are recorded at various pressures (0.001–5 mbar) to optimize the S/N ratio for band systems appearing at different energy regions. The spectral region below 70,000 cm^?1 has contributions from dissociation mechanism of the ground state of OCS and three valence band systems arising from promotion of a 3π electron to 4π and 10σ orbital. Improved S/N ratio helped in unambiguous assignment of the valence band progressions at 42,000–48,000 cm^?1, 53,000–62,000 cm^?1 and 63,500–70,000 cm^?1 regions to the ¹Δ←X¹Σ⁺ transition, the relatively intense and sharp bands of ¹Π←X¹Σ⁺ transition and intense but broad bands of ¹Σ⁺←X¹Σ⁺ transition, respectively, and obtain the vibrational frequencies. Above 70,000 cm^?1 Rydberg series arising from s, p, d and f orbitals converging to the ionic ground state X²Π of OCS⁺ (90,121 cm^?1) are identified. Long progression in the first few members of the Rydberg series is suggestive of mixed valence character. Quantum defects are evaluated and used to discuss the nature of the molecular orbital. The present study provides a unifying picture of the VUV photo-absorption spectrum of OCS up to its first ionization limit.     

Infrared bands of HCl and DCl by Fourier transform spectroscopy: Dunham coefficients for HCl,DCl, and TCl

Fourier absorption spectra of HCl and DCl are recorded simultaneously in the spectral range [2840 cm^?1–8450 cm^?1]. A U_ij reduced Dunham coefficient set is deduced by fitting all the available data and then used together with four mass-scaling parameters to predict the TCl Y_ij Dunham coefficients.     

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.     

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.     

Diffusionskonstante und charakteristische Absorption vor der Bandkante von Mn in ZnO-Kristallen

ZnO single crystals were doped with Mn and Co by diffusion. In the temperature range from 1400–1600 K the Mn and Co-diffusion-constants were determined:D _Mn=3.2 · 10^?3 exp (?2.87 eV/kT) cm² sec^?1 andD _Co=1·10exp(?3.98 eV/kT) cm² sec^?1. The Mn doped ZnO crystals show a characteristic colour due to an absorption near the intrinsic absorption edge. The corresponding absorption spectra were measured forE⊥c andE∥c. A discussion of different absorption mechanism shows that a charge-transfer transition is responsible for this absorption.     

Vibrational spectra of a GaS single crystal

The Raman and infrared active long wavelength phonons of a GaS single crystal were studied at different temperatures in the 10–600 cm^?1 range. Properly polarized Raman spectra could be obtained with the 4880 Å exciting line and the previous assignment of the E_1g modes controversed recently could be confirmed. Infrared spectra were recorded in the 30–600 cm^?1 region. The vibrational frequencies of the crystal were also calculated using a method developed by Wieting and six new frequencies corresponding to infrared and Raman inactive modes have been proposed.We have observed that the degree of leakage of scattered intensity in unallowed polarizations increases when the wavelength of the exciting line moves off the exciton absorption front. The phonon at 74 cm^?1 was particularly sensitive and the question of the antiresonant behaviour of this compound is raised.     

Self-broadening of principal series lines of rubidium at high number densities and oscillator strengths

The self-broadening of principal series lines of rubidium and the corresponding oscillator strengths have been measured using a steel absorption tube heated up in an electric furnace. The line profiles were obtained from absorption measurements using a grating spectrograph of high resolution in the temperature range of 340–490 °C; the number densities varied from 5 · 10¹⁶ to 8 · 10¹⁷cm^?3. The half widths deduced from the absorption profiles disagree with the classical impact approximation based on dipole-dipole interaction but approach closely the asymptotic values of the quantum-mechanical Reinsberg theory and of the “short-range”-calculations of Presnyakov. Oscillator strengths for the higher series lines were evaluated from the spectra agreeing very well with the asymptoticn ^*?3-hydrogen-like slope of the values.