Electronic Absorption Spectra of Some Fluoroaminotoluenes

Abstract

The near ultraviolet absorption spectra of 2-fluoro-5-amino-; 3-fluoro-4-amino-, 3-fluoro-6-amino-and 4-fluoro-2-aminotoluene have been investigated in vapour phase. The strongest band appearing at 2887.5 Å (34621 cm^?1), 2966.1 Å (33704 cm^?1), 3026. 7 Å (33029 cm^?1) and 2891.4 Å (34575 cm^?1) in the respective molecules has been identified as the 0,0 band. All the bands have been analysed in terms of some ground and excited state fundamentals. The assignment of the fundamental frequencies to the probable modes of vibration have also been discussed.     

The Electronic and Infrared Absorption Spectra of Toluene-d

Abstract

The infrared and ultraviolet absorption spectra of toluene-d have been investigated for the first time in the regions 400 - 4000 cm^?1 and 2350 ?2750 A° respectively. The intense band at 2666.3 A°(37494 cm^?1) in the u.v. vapour absorption spectrum has been identified as the o,o band and others have been interpreted in terms of the three (519,632 and 785 cm^?1) ground state and the six (454,526,743,935,963 and 1180 cm^?1 excited state fundamentals. The correlation of the various frequencies of the ground and excited states of toluene and toluene-d has been done. The observed isotopic shift for toluene-d is 14 cm^?1.     

Electronic Absorption Spectra of 2-Fluoro-4-bromo, 4-Fluoro-2-bromo and 2-Fluoro-5-bromo Toluenes

Abstract

Absorption spectra of 2-Fluoro-4-Bromo, 4-Fluoro-2-Bromo and 2-Fluoro-5-Bromo Toluenes have been investigated in the near ultraviolet region in vapour phase. The band systems correspond to allowed transitions with the most intense bands at 2742.09 Å (36458 cm^?1), 2745.96 Å (36406 cm^?1) and 2771.74 Å (36068 cm^?1) identified as 0,0 transitions in 2-Fluoro-4-Bromo, 4-Fluoro-2-Bromo and 2-Fluoro-5-Bromo Toluenes respectively. The bands in 4-Fluoro-2-Bromo Toluene have been analysed in terms of the ground state fundamental 208 cm^?1 and excited state fundamentals 244, 611, 855 and 1211 cm^?1 and the bands in 2-Fluoro-4-Bromo and 2-Fluoro-5-Bromo Toluenes are explained in terms of the upper state fundamentals 716, 987 and 1230 cm^?1 and 722, 886 and 2130 cm^?1 respectively.     

Electronic Absorption Spectrum of Mesitylene Vapour

Abstract

The electronic absorption spectrum of mesitylene vapour has been photographed on a Q-24 Medium Quartz Spectrograph. The molecule belongs to D_3h symmetry and the transition is A→₁A₂ which is forbidden and due to that the (0,0) band does not appear in the spectrum. The position of (0,0) band in this case has been fixed at 36562 cm^?1 with the help of 0→1 and 1→0 transitions. There are 66 bands and most of them are assigned in terms of two ground state frequencies of magnitudes 278 and 519 cm^?1 and 7 excited state frequencies of magnitudes 267, 436, 554, 968, 1268, 1386 and 1575 cm^?1     

Vibration-rotation bands in ethane

The absorption spectrum of ethane was recorded at 0.014 cm^?1 resolution in the range 4500–6500 cm^?1 using a Fourier transform spectrometer and at room temperature. Eighteen bands could be identified and their type assigned. Upper state rotational constants are provided for the band at 5948.338 cm^?1 and Coriolis constants are obtained for most perpendicular bands. Vibrational assignments are suggested for the bands at 5948 cm^?1 (v7 + v10), 5914 cm^?1(v8 + v ₁₀+ v ₁₁), and 5852cm^?1 (v ₅+v ₁₀). All vibrational bands reported in the literature are gathered.     

Irradiation and heating effects in amethyst crystals from brazil

Abstract

In this work we report optical absorption spectroscopy study of thermal and irradiation effects on samples of amethyst from Minas Gerais and Rio Grande do Sul, Brazil. Three bands were studied: 10500 cm^?1 (k), 18300 cm^?1 (θ) and 28000 cm^?1 (ζ). Thermal and irradiation effects shows that the θ and ζ bands belongs to a same center and the k band to another center. The isothermal decay and irradiation growth of these band reveal a complex kinetics. The optical absorption bands of amethyst from Minas Gerais do not recover the prmitive absorbance after being bleached at 470°C and irradiated. This sample heated at 470°C in highly reducing atmosphere gets a yellow-brown color. The amethyst from Rio Grande do Sul treated at 400°C gets, also, a yellow-brown color. We suggest this color is probalbly due to the formation of Fe₂O₃ submicroscopc segregate crystals due to the diffusion of Fe ions and oxygen vacancies.     

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.     

IR Absorption and Raman spectroscopic study of reentrant-nematic liquid crystalline N-[4-(4-Octyloxy-benzoyloxy) Benzylidene]-4-Cyanoaniline (OBBC)

Abstract

The IR absorption and Raman scattering of OBBC have been investigated in the solid, ReN, SmA and nematic phases. The intensity of the 2229 cm^?1 band assigned to the C[tbnd]N stretching mode decreases with increasing temperature in the reentrant nematic phase; this is attributed to a change in the overlap of the molecules. While the IR bands at 1728 and 841 cm^?1 also show a remarkable temperature dependence, Raman bands do not show significant temperature dependence in the liquid-crystal phases.     

New optical absorption spectra of Cu2 molecules produced by the gas evaporation technique

A study was conducted on the optical absorption spectra ranging from 233 to 285 nm, which were taken in a region close to the source of evaporation of Cu, in low-pressure helium gas of 100 Torr. Eight band systems for Cu₂ dimers designated as system 1 through 8 were identified. The spectroscopic constants for the band origins were derived as follows: [vtilde] ≈ 42 200 cm^?1 for system 1, [vtilde]₀₀ = 41 604.74cm^?1 for system [vtilde]₀₀ = 39 606.70cm^?1 for system [vtilde]₀₀ = 38 124.32cm^?1 for system 4, [vtilde]₀₀ = 38 048.65 cm^?1 for system 5, 98, [vtilde]₀₀ = 36 834.22cm^?1 for system 6, [vtilde]₀₀ = 36 341.55 cm^?1 for system 7 and [vtilde]₀₀ = 36 174.99cm^?1 for system 8. For all cases in which vibrational constants of the lower state could be determined, it was found that the transition originated from the ground state of Cu₂.     

Resonant and localised modes due to boron in gallium arsenide

Silicon-doped n-type GaAs crystals pulled from a melt encapsulated with boric oxide exhibit an IR absorption band at 123 cm^?1 as well as a number of localised-mode bands associated with boron and silicon. Evidence is presented which leads us to attribute the band at 123 cm^?1 to a resonant mode associated with isolated B atoms on Ga sites. Other crystals containing high concentrations of silicon or phosphorous did not show such an absorption band. The results are discussed briefly in terms of the simple mass defect model for impurity vibrations.     

Vibrational Spectroscopy of the Borate Mineral Priceite—Implications for the Molecular Structure

ABSTRACT

Priceite is a calcium borate mineral and occurs as white crystals in the monoclinic pyramidal crystal system. We have used a combination of Raman spectroscopy with complimentary infrared spectroscopy and scanning electron microscopy with Energy-dispersive X-ray Spectroscopy (EDS) to study the mineral priceite. Chemical analysis shows a pure phase consisting of B and Ca only. Raman bands at 956, 974, 991, and 1019 cm^?1 are assigned to the BO stretching vibration of the B₁₀O₁₉ units. Raman bands at 1071, 1100, 1127, 1169, and 1211 cm^?1 are attributed to the BOH in-plane bending modes. The intense infrared band at 805 cm^?1 is assigned to the trigonal borate stretching modes. The Raman band at 674 cm^?1 together with bands at 689, 697, 736, and 602 cm^?1 are assigned to the trigonal and tetrahedral borate bending modes. Raman spectroscopy in the hydroxyl stretching region shows a series of bands with intense Raman band at 3555 cm^?1 with a distinct shoulder at 3568 cm^?1. Other bands in this spectral region are found at 3221, 3385, 3404, 3496, and 3510 cm^?1. All of these bands are assigned to water stretching vibrations. The observation of multiple bands supports the concept of water being in different molecular environments in the structure of priceite. The molecular structure of a natural priceite has been assessed using vibrational spectroscopy.     

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.     

A study of the fundamental and first overtone bands of NO in NO-rare gas mixtures at pressures up to 10,000 PSI

The absorption intensities of the 1-0 and 2-0 vibration-rotation bands of NO are determined from the absorption coefficients of NOHe and NOAr gaseous mixtures at high pressures at room temperature. The values obtained are: A_1-0 = 121 ± 6 cm^?2 Agt^?1 and A_2-0 = 2.17 ± 0.11 cm^?2 Agt^?1. A theory developed by Tipping is applied to evaluate the dipole moment coefficients unambiguously, including their signs, from the absolute intensity values and the difference between the mean frequency factor and the band origin. The following expansion for the dipole moment function in the ground state of NO is determined: M(x) = ?0.166 + 2.54x ? 1.99x² (in Debye). The absorption profiles of both the 1-0 and 2-0 bands in NOAr mixtures show marked changes as gas pressure increases; some of the factors influencing the shapes of the bands are also discussed. The plots of the integrated intensity vs rare gas density are found to be straight lines with positive slopes. This linear increase of the band intensity with density is interpreted as mainly due to the apparent induced absorption.     

High resolution FTIR spectra and analysis of the ν11 fundamental and of the ν2 + ν11, ν5 + ν12 and ν7 + ν16 combination bands of 12C6D6

We report results from measurements of the high resolution FTIR spectrum for the fully deuterated benzene molecule C₆D₆ in the range 450–3500 cm^?1. Accurate spectroscopic constants have been obtained for the fundamental vibration ν₁₁ at 496.208 cm^?1 and improved ground state constants have been deduced from a fit of ground state combination differences. The J structure of the combination parallel bands ν₂ + ν₁₁ (at 2798.1 cm^?1), ν₅ + ν₁₂ (1802.5 cm_?1) and ν₇, + ν₁₆ (2619.3 cm^?1) of C₆D₆ has been analysed as well, from which improved values of the band origin and of the B and D _j constants of the excited states have been obtained. The strongest hot bands accompanying these parallel transitions have been assigned by means of the anharmonic force field calculated by Maslen et al. [1992, J. chem. Phys., 97, 4233]. In particular (ν₁₁ + ν₁₆) ? ν₁₆ is assigned to the band at 492.4 cm^?1 even though its shape is typical of a perpendicular transition (PAPE). New values for the ν₅, ν₁₂ and ν₁₆ band origins are determined from the band origins of combination bands and from calculated anharmonic constants. Numerous anharmonic constants are derived from the assignment of hot band and combination transitions.     

Electronic Absorption Spectrum of Fe3+ Doped in Ammonium Perchlorate Single Crystal

Abstract

Single crystals of Iron - doped ammonium perchlorate were grown at room temperature. The electronic absorption bands observed at room and liquid air temperatures have been assigned transitions from the ground ⁶A_1g state to the excited ⁴A_1g, ⁴E_g, ⁴T_1g and ⁴T_2g states. The crystal field parameters Dq = 870 cm^?1, B = 615 cm^?1 and C = 4.2 B are found to give a good fit to the observed band positions.     

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 Quantitative Study of Acetylation of Microspheres of Polystyrene

Abstract

Fourier transform infrared spectroscopy has been used to study quantitatively the acetylation of monodisperse polystyrene microspheres with diameters ranging from 7 to 9μm. The CH₂ stretching infrared vibration mode at 2921 cm^?1 was used as the internal intensity standard. The acetylation extent could be easily measured by comparing the relative intensities of the bands of acetyl group (1678, 1415, 1359 cm^?1) or the bands due to the para-substituted benzene ring to the band at 2921 cm^?1 from the calibration curve.     

Laser-induced Raman scattering in calcium titanate

The Raman spectrum of polycrystalline calcium titanate prepared by a liquid mix technique and heated to 800°C has been recorded at room temperature using an argon-ion laser as exciter. The observed spectrum was interpreted on the basis of factor-group C_2V. Not all of the Raman active modes predicted by factor group analysis were observed and this could be due to: over-lapping of bands, or very low polarizabilities of some of the modes or masking of the weak bands by intense bands. The band at 639 cm^?1 is tentatively assigned to the TiO symmetric stretching vibration (γ₁) and the bands at 495 and 471 cm^?1 to torsional modes. The bands in the region 180–340 cm^?1 are assigned to the OTiO bending modes and the 155 cm^?1 band to the Ca(TiO₃) lattice mode. The observed Raman bands are compared with the available infrared absorption data and, as expected, some coincidences in frequencies are seen for this compound with a noncentrosymmetric structure.     

Dielectric-field effect correction on i.r. band shapes in the liquid phase

The dielectric-field correction on i.r. band shape in the liquid has been studied by using the Lorentz internal field. The deformation of the band shape is inappreciable for a weak absorption band that becomes measurable only at a sample thickness larger than 10μ. The shapes of the strong singlet and doublet bands of hexafluorobenzene at 1530 cm^?1 and near 1000 cm^?1, respectively, and also of the doublet band of carbon tetrachloride near 790 cm^?1 have been measured in dilute solutions and compared with those for the pure liquid.     

Anti-stokes emission in an additively colored KCl caused by excitation with a Nd: YAG laser

Abstract

We have observed the quadratic laser power dependence of two anti-Stokes emission bands at 15100cm^?1 and 14000cm^?1 in an additively colored KCl when excited with a Nd:YAG laser. The cross section of two photon absorption to cause the 14000cm^?1 band is estimated to be 4×10^?40cm⁴sec. We have observed that emission intensities are dependent on temperature in the range between 4. 2K and 130K. They are enhanced by means of optical bleaching and also with the increase of the F concentration. From a qualitative analysis of these observations, we propose that these emissions are correlated to the loose aggregation of the F centers.