Showing papers on "Absorption band published in 1969"

Predissociation in diatomic spectra with special reference to the Schumann-Runge bands of O2

Abstract: It is shown how the predissociation probabilities for the vibrational levels of a bound state of a diatomic molecule, crossed by a repulsive state may be calculated, knowing accurate potential energy curves for both. The expected maximum occurs for vibrational levels near the crossing point but several subsidiary maxima may occur above this. It has been found that the results are very sensitive to the form of the repulsive curve. For the Schumann-Runge absorption band of O2 we find the observed predissociation can be explained by a single crossing near v' = 4 by a repulsive curve having the form:

Spectroscopic Differentiation of the Electron‐Accepting Sites in Fungal Laccase

Abstract: 1 The difference specrum between oxidized and reduced fungal laccase at pH 5.5 shows an absorption band at 330 nm in addition to the visible absorption band at 610 nm. 2 The 610 nm band and the 330 nm band are reduced together in a linear fashion with the addition of 3.5 electron equivalents of ascorbate. 3 Titration of laccase in the presence of 3 mM fluoride leads to a differentiation of the electron-accepting site in the molecule. The 610 nm band is found to be associated with a single electron-accepting site and the 330 nm band is associated with a two electron-accepting site. Electron paramagnetic resonance analysis during the titration indicates that neither the Type 1 Cu2+(the “blue” Cu2+) nor the Type 2 Cu2+ (the “non-blue” Cu2+) are associated with the 330 nm band. 4 Titration of laccase at pH 8.3 with quinol also associates the 330 nm band with a two electron-accepting site. 5 Preliminary stopped-flow kinetic measurements on the absorbance changes at 330 nm and 610 nm are described and the results suggest an involvement of the component responsible for the 330 nm band in the catalytic reaction. 6 The nature of the component responsible for the 330 nm band is discussed in the light of these results and our previous titration results. The findings are consistent with the 330 nm band being associated with the two additional copper atoms in the molecule and agree with our previous suggestion that these copper atoms exist as an electron-accepting Cu2+ -Cu2+ pair in the oxidized protein.

Polarization Assignments of the Electronic Spectrum of Purine

Abstract: Polarized reflection spectra of the (100) face of purine crystals have been measured to 185 mμ. The corresponding absorption spectra which are computed by a Kramers–Kronig transformation of the reflection spectra are analyzed so as to assign the transition moment directions of the electronic absorption bands. The analysis is made assuming the oriented‐gas model and again for a case which treats intermolecular interactions. The polarization of the first absorption band (λmax = 294mμ) is out‐of‐plane as expected and is consistent with an n → π* assignment. The next band at 263 mμ is polarized in‐plane (π → π*) at + 48° from the C4 − C5 axis (toward C6). The weak band at 250 mμ in the crystal is another perpendicular n → π* transition. The strong absorption in the 200‐mμ region and below can be plausibly assigned as two transitions. One (at 200 mμ) is polarized in nearly the same direction as the 263‐mμ band. The other band, at 190 mμ, can have reasonable intensity relative to the solution spectrum only if i...

Vacuum Ultraviolet Absorption Spectra of Synthesized Polymer Films

Abstract: The optical absorption spectra of paraffin, polyvinylchloride, isotacticpolystyrene, atacticpolystyrene, poly-p-chlorostyrene, poly-p-methylstyrene, poly-o-chlorostyrene, poly-3, 4-dichlorostyrene, polyvinylcarbazole, polymethylmethacrylate, polyacrylonitrile, polyethyleneglycols, and polybutadiene were measured over the wavelength range from 2500A to 1100A in order to study the electronic structure of polymer films. A broad absorption band begins from about 1600A to the shorter wavelength side common to all polymers, and this band is interpreted due to the main chain electrons. From about 1600A to the longer wavelength side, various absorption spectra are found, which are similar in almost every eases to the absorption spectra of corresponding monomer molecules only shifted to the longer wavelength side. These shifts are interpreted due to the expansion of side chain electron cloud.

Optical Absorption and Luminescence of Irradiated Mg F 2

Abstract: A study of the temperature and polarization dependence of the absorption and luminescence from electron and neutron-irradiated Mg${\mathrm{F}}_{2}$ crystals has been made. The absorption band at 260 nm is accepted as due to an $F$ center, and excitation, when other centers are absent, produces an emission at about 430 nm. Two other absorption bands at 370 and 400 nm arise from different types of $M$ centers, and our data suggest that these centers give rise to emission bands at 420 and 600 nm, respectively. Several narrow absorption lines are observed in both electron-and neutron-irradiated samples. From polarization studies and optical bleaching treatment, the lines at 387.2, 385.7, 384.5, 382.3, and 380.8 nm are identified as zero-phonon and phonon-assisted transitions of the defect responsible for the 370-nm band. A comparison is made between the vibrational energies associated with the phonon-assisted lines and the dispersion relationships calculated for Mg${\mathrm{F}}_{2}$.

Infrared Optical Absorption in Semiconducting Cd F 2 :Y Crystals

Abstract: The infrared optical absorption band associated with yttrium (Y) donors in semiconducting Cd${\mathrm{F}}_{2}$ has been measured over a broad range of donor concentration and temperature. The results are presented and discussed in terms of continuum theories for the electron energy states of isolated hydrogenlike centers in polar materials. The general features of the optical absorption are approximately described in terms of the nonadiabatic approximation, in which the lattice is polarized to a considerable extent by the instantaneous position of the electron. By assuming that the donors tend to form clusters, apparent discrepancies between the optical and transport properties can be resolved. Impurity-banding effects, which are extremely important in determining the transport properties, are relatively unimportant in interpreting the observed optical absorption.

New electronic transitions of the C2 molecule in absorption in the vacuum ultraviolet region

Abstract: Three new electronic transitions of the C2 molecule have been observed in absorption in the region 1300–1450 A. The system of shortest wavelength is readily identified as a 1Πu–1Σg+ transition; the...

Electronic Structure of Tris(1,10-phenanthroline)iron(II) Complex

Abstract: The SGF MO’s for the π-electron system of 1,10-phenanthroline have been determined by following the Pariser-Parr-Pople’s treatment. For the description of the lower excited states, the configuration interaction among nineteen singly-excited configurations with lower energy has been taken into account. The electronic spectrum of 1,10-phenanthroline has been interpreted on the basis of the results of the theoretical calculation. The SCF MO’s for the π-electron system of a coordinated 1,10-phenanthroline in the tris-iron(II) complex have been determined to be self-consistent under the electrostatic potential field of the central metal ion and the other ligand molecules. On the basis of the results for coordinated ligand, the π-electronic structure of tris-(1,10-phenanthroline)iron(II) ion has been investigated from the theoretical point of view. It has been shown that two kinds of the charge-transfer transitions are responsible for an intense absorption band in the visible region, namely electron transfers f...

Electron-lattice interaction in the absorption spectra of thallium doped alkali halides

Abstract: The electron-lattice interaction of NaCl:Tl+, KCl:Tl+, KBr:Tl+, and KI:Tl+ is discussed using the moments of the absorption bands. The discussion is based on a theory ofToyozawa andInoue andHonma. Consistency of the data is found for the absorption measurements. An analysis of the band shift under applied stress shows for theA-band in KCl and KBr and for theA- andB-band in KI that the electronlattice coupling constants derived from these data assuming next neighbour interaction differ considerably from those derived from the second moments of the bands.

Vacuum-ultraviolet Absorption Spectra of Aliphatic Ketones

Abstract: The molar-absorptivity curves of various aliphatic ketones, mainly methyl alkyl ketones, in the gaseous state in the region from 1650 to 2000 A have been obtained. In these ketones the absorption bands near 1950 A and 1700 A are denoted as A and B bands respectively. Di-n-propyl and diisopropyl ketones show, besides the A and B bands, an absorption band near 1650 A (C band). The relations between the obtained spectra and the molecular structures of these ketones have been studied. On the basis of this study, the characteristics of the electronic transitions of A, B, and C bands have been discussed.

Absorption Spectrum of Vaporized Titanium Monofluoride

Abstract: The electronic absorption spectrum of TiF(g) has been obtained utilizing the techniques of flash heating and kinetic spectroscopy. No spectroscopic data have previously been reported for this molecule, which is observed in the vapor only during the preparative photoflash. The spectrum may be produced by the flash heating of powdered TiF3 or TiF4. It may also be obtained from the powdered metal flashed in the presence of CF4, SF6, or solid aluminum trifluoride. Three band systems have been observed, the main system occurring in the region 3930–4088 A. The other two systems are in the regions 3855–3906 A and 3650–3775 A. The principal spectroscopic features resemble those of TiCl obtained by flash heating TiCl3(s) or Na2TiCl4(s). A vibrational analysis of the main system of TiF shows it to be a Δυ = 0 sequence for the transition from the 4Σ−(δ2σ) ground state to a 4Π(δ2π or δσπ) excited state. An absorption band attributed to the (1, 0) transition is consistent with ωe″ = 593 cm−1. A number of bands remain ...

Magnetic and Optical Properties of Aromatic Hydrocarbon Cation Radical Salts

Abstract: Stable cation radical salts were prepared by oxidation of perylene, 9,10-diphenylanthracene, 9,10-dimethylanthracene, and 9,10-dichloranthracene with antimony pentachloride. Perylene perchlorate was also obtained in a stable form. From the temperature variations of their paramagnetic susceptibilities, the exchange coupling constants for these salts were found to increase in the sequence of above listing ranging from ∼0 to 8.5×10−2 eV. The absorption spectra of these solid compounds were compared with those observed with solutions. While the absorption bands of each salt in the visible region were found to correspond to those of the solution spectrum of the respective compound, an extra absorption band was observed in the near-infrared region for compounds with larger exchange coupling constants. The appearance of the new absorption band was reasonably ascribed to charge-transfer interaction between the radicals. These observations are considered to support further our previous suggestion that the magnitud...

Photo-isomerization and the triplet state of stilbene

Abstract: Cis- or trans-stilbene were isomerized in solution by irradiation within the singlet-triplet absorption band in the presence of O2. No photocyclization to phenanthrene was found. The quantum yields for cis → trans and trans → cis isomerization are 0.22 ± 0.04 and 0.42 ± 0.03, respectively. Known experimental evidence is interpreted as supporting an existence of two non-equivalent energy minima, in twisted configurations, of the lowest triplet state of stilbene.

Infrared absorption spectra of atmospheric dust over an interior desert basin

Abstract: Based on the qualitative microspectrophotometric analysis of 287 atmospheric dust samples taken within the surface boundary layer over south central New Mexico, U.S.A. from May 1966 through October 1967, a representative infrared absorption spectrum from 4000 to 250 cm−1 (2.5 to 40 μm) is presented. The strongest absorption band is centered at 1027 cm−1 (9,7 μm), within the 1250 to 770 cm−1 (8 to 13 μm) atmospheric window, and is silicate induced. Two other strong broad absorption bands are the carbonate band at 1425 cm−1 (7.0 μm) and the silicate band at 468 cm−1 (21.4 μm). Temporal variations in the absorption spectra of the dust are observed primarily in the varying relative intensities of the 1027 and 1425 cm−1 (9.7 and 7.0 μm) absorption bands and in the occasional enhancement of the 1027 cm−1 (9.7 μm) band caused by sulfates in the dust. This study indicates that there is a close similarity between the absorption spectra of the atmospheric dust and the spectra of the small particle fraction of area soils, and between the representative dust spectrum and a spectrum of a synthetic mixture (by weight) of 80% silicates, 16% carbonates, and 4% nitrates.

Circular dichroism of nucleoside derivatives, vi. the optically active bands of adenine nucleoside derivatives

Abstract: The circular dichroism data on 17 adenine nucleosides show that the 260- and 207-mμ absorption systems of the adenine chromophore each contain at least two electronic transitions. The CD maxima are commonly found at around 260, 220, and 200 mμ, and occasionally at 240 mμ. Solvent studies suggest that these CD bands arise from pi-pi* transitions. A weak absorption band that obeys the McConnell criteria of an n-pi* band is resolved at about 290 mμ in hydrocarbon solvents. This band exhibits very little rotatory power.

Absorption and fluorescence spectra of crystalline trans-stilbene

Abstract: Measurements on polarized absorption and fluorescence of a single crystal of trans-stilbene are reported. Vibrational analysis is also reported for them. The a:b polarization ratio in the absorption of a pure trans-stilbene crystal deviates greatly from the oriented gas model value. The fluorescence origin of the pure crystal at 300 °K is 340 cm−1 to the long-wavelength side of the 0-0 absorption band. On lowering the temperature to 90 °K the intensity of fluorescence near the origin decreases and a red shift of 50 cm−1 to 100 cm−1 is found. It is suggested that the fluorescence is due to a trapped exciton located at some lattice imperfection and that, at low temperature, a part of the fluorescence originates from a lower defect level.

Presscure‐Induced a″ 1Σg+ ← X 1Σg+ Absorption in the Vacuum Ultraviolet Spectrum of Molecular Nitrogen

Abstract: The a″ 1Σg+–X 1Σg+ absorption band of N2, which has been reported recently in a preliminary communication, has been investigated at nitrogen pressures from 10 to 80 torr. A study of the absolute absorption coefficient and of its pressure dependence shows definitely that the observed band arises as a pressure‐induced dipole transition at the quoted pressures. The integrated absorption represents an absolute oscillator strength of f / p = 3.2 × 10−8torr−1. The large bandwidth (400 cm−1) is attributed to the short duration of the dipole‐inducing collisions: 1.3 × 10−14 sec on the average. Thus the observed intensity can be interpreted in terms of an average oscillator strength of f = 0.04 per molecule per collision. The apparent optical quadrupole absorption f value of less than 10−7 corresponds to a very small quadrupole matric element compared to the one which determines the electron excitation cross section. A search for the a″–X quadrupole emission band in the electron‐beam‐excited spectrum at very low p...

Induced Absorption Band in the N Region of LiF Crystals by Charged Particle Irradiation at Liquid Nitrogen Temperature

Abstract: Single crystals of lithium fluoride have been irradiated with deuterons or protons at liquid nitrogen temperature. In absorption spectra of the crystals immediately after irradiation, a band is observed at 542 nm in addition to the F and M bands. This band has an almost constant intensity during warming from LNT to RT. It is obscured by the other overlapping bands when the crystal is heated about 100°C or when this is aged at RT for a long time. The nature of this band is examined in connection with the so-called N 2 band, Farge's I band and Vander Lugt's N c band. The following relation is believed to be most plausible: The observed absorption band is identified with the I band. The N 2 band is identified with the N c band but may not be identified with the I band.

Electronic Absorption Spectra of the Alkali Metal Complexes with Bipyridine

Abstract: Electronic absorption spectra of the alkali metal complexes with 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipyridine or 5,5′-dimethyl-2,2′-bipyridine have been observed in tetrahydrofuran solutions. Each spectrum has four major bands in the near infrared, visible and near ultraviolet regions, and is essentially due to the π–π*transitions in the negative ion (extra π electron trapping state) of bipyridine or its dimethyl derivatives coordinating to a metal ion. The band about 18000 cm−1 is the most sensitive to the metal ion species involved and assigned to a transition with the polarization parallel to the short axis of the bipyridine molecule. Each absorption band of the bipyrdine negative ion shows characteristic spectral shift upon CH3-substitutions in its peripheral positions. This CH3-substitution effect on the absorption spectra of bipyridine negative ion is quite different from that of complexes including neutral bipyridines and gives a basis of the criterion to determine whether the coordinating bipyri...

Free Electron Model for the Absorption of Oxygen-bridged Binuclear Complexes in the Near Ultraviolet

Abstract: CERTAIN binuclear complexes of cobalt or copper with an oxygen bridge between the metal ions have an absorption band in the near ultraviolet which has been called the “peroxy-specific band”1. We may consider these complexes to have contributing canonical forms in which the metal ions can choose between oxidation numbers n and (n + 1) and the oxygen bridge can be an oxygen molecule, a superoxide ion or a peroxide ion, as follows The various configurations are expressions of the fact that the metal ions can have a partly filled 3d sub-shell in the complexes discussed here, and the oxygen bridge can also be considered to have a partly filled shell containing two, three or four electrons according to the kind of bridge in the configuration.

Cotton–Mouton Effect through an Absorption Band

Abstract: Cotton–Mouton dichroism was measured for an aqueous solution of europium trichloride. The experiment was performed at room temperature through the visible 7F0 → 5D1 absorption band. A phenomenological theory is given for the results thus obtained. The spectroscopic splitting factor of the excited state is determined and is shown to be in close agreement with that obtained independently through Faraday effect measurements. Optimal experimental conditions are pointed out for further work in the field.