Shoulder Band Research Articles

SERS study of the adsorption of gelatin at a copper electrode in sulfuric acid solution

The adsorption of gelatin at a copper electrode in sulfuric acid solution has been investigated in situ by SERS spectroscopy. The adsorption of gelation at the copper electrode is supported by the presence of shoulder bands at 260 and 326 cm −1 in all SERS spectra for gelatin, which are assigned to CuN vibrational modes, indicative of molecular adsorption via the nitrogen-containing amino acid groups of the molecule. The adsorption of gelatin at the copper electrode is dependent on electrode potential and, furthermore, is accompanied by coadsorption of anion species. In electrolytes containing low chloride concentrations, halide coadsorption with gelatin occurs at less negative potentials, while sulfate is observed as the coadsorbed species at more negative potentials. In solutions of high chloride concentration, the halide ion is present on the electrode surface over the entire potential range investigated. Additionally, it is apparent that chloride may enhance the adsorption of gelatin at the electrode surface owing to an interaction between the surface adsorbed chloride and the amine groups of the gelatin molecule.

Infrared spectroscopy on lead silicate glass

The reflectance spectra of some lead silicate glasses of general formula (PbO)x(SiO2)y have been measured in the infrared frequency range from 50 to 4000 cm−1. The dispersion and absorption spectra in the range 50–2000 cm−1 have been calculated from the reflectance data using the Kramers-Kronig relations. The band at ∼ 135 cm−1 is assigned to the stretching vibration of lead-oxygen bonds. The shoulder band of the silicon-oxygen stretching mode at ∼900 cm−1 shows a weak coupling of those bonds to the Pb2+ modifier. The vibration strength of those bands shows that the number of the Pb2+ modifier increases first up approximately to 50 Mol% with the increase of PbO content and then decreases rapidly. It indicates that different PbO content causes different structural forms in lead silicate glasses: The addition of small amounts of PbO to vitreous silica serves to modify the continuous three-dimensional silica network: whereas in those glasses with a high lead content, the influence of the cation, Pb2+, appears to lie between that of network former and network modifier. This result is in agreement with the structural model of Worrel and Henshall.

X-ray analysis and IR absorption spectra of Li-Ge ferrite

X-ray diffraction and IR spectroscopy have been used to study the mixed ferrite Li 0.5+0.5 x Ge x Fe 2.5−1.5 x O 4 (where x = 0.0, 0.2−0.5. The X-ray diffraction data established that the prepared samples were homogeneous and that spinel structure was formed. The lattice parameter for each composition was calculated; the lattice parameter of the sample with x =0.0 was 0.832 nm, and that for x=0.2−0.5 had a constant value of ≈0.828 nm. IR spectra were recorded in the range 200 to 1200 cm −1. Three main bands were observed. The band at ≈600 cm −1 ( ν 1) and the band at ≈400 cm −1( ν 2) were assigned to the tetrahedral and the octahedral complexes, respectively. A small band ( ν 3) at ≈350 cm −1 indicated the presence of octahedral divalent metal-oxygen in the complexes. When Ge content was introduced, a shoulder band appeared at 790 cm −1. This band can be related to the stretching vibrational modes of GeO 4 tetrahedra.

The Amino–Imino Tautomerization of the 2-Aminopyridine–Acetic Acid System in Isooctane

Abstract The UV absorption spectra of 2-aminopyridine were measured in isooctane (2,2,4-trimethylpentane) containing various amounts of acetic acid at room temperature; the temperature dependence (20–−80°C), of the spectra was also determined, while the concentration of acetic acid was maintained constant. An additional shoulder band appeared around 335 nm in the spectra obtained when the acetic acid concentration was higher than 1×10−2 mol dm−3. The band corresponding to the 335 nm band was observed for monomethyl-substituted 2-aminopyridine. The 335 nm band was assigned to the π–π* transition of the (E)-2(1H)-pyridinimine moiety in the 2-aminopyridine-acetic acid complex. The proton transfer from acetic acid to 2-aminopyridine in the complex may be difficult energetically in the ground state.

The Amino-Imino Tautomerization of 2,6-Diaminopyridine by Interaction with Ethanol

Abstract The UV absorption spectrum of 2,6-diaminopyridine was measured in an ethanol-and-isooctane mixed solvent while increasing the concentration of ethanol at room temperature and changing the temperature from 20 to −100°C at a constant concentration of ethanol. Its spectrum showed a clear shoulder band near 345 nm as the concentration of ethanol increased to over 5×10−1 mol dm−3 at room temperature and as the temperature decreased from 20 to −100°C in 1×101 mol dm−3 of ethanol in the isooctane solution. The corresponding band near 345 nm was observed for 2-amino-6-methylaminopyridine and 2,6-bis(methylamino)pyridine; however, it was not found for 2-amino-6-dimethylaminopyridine, 2-methylamino-6-dimethylaminopyridine, or 2,6-bis(dimethylamino)pyridine in the same experiments. The shoulder band near 345 nm was, on the basis of the spectroscopic results and the molecular orbital method, assigned to the π–π* absorption band of the (E)-6-amino-2(1H)-pyridinimine formed through the hydrogen-bond formation of 2,6-diaminopyridine with two ethanols. The formation of the imino form with two ethanols may be restricted to the 2,6-diaminopyridine and its methyl derivatives, in which each amino group at the 2- and 6-positions has at least one hydrogen atom. The proton transfer from ethanol to 2,6-diaminopyridine in the 2,6-diaminopyridine-ethanol complex may be energetically difficult in the ground state.

Raman spectra of diamondlike amorphous carbon films

Raman spectra of the diamondlike amorphous carbon (a-C) films prepared by the plasma CVD method have been measured as a function of the excitation wavelength. A Raman band centered at about 1530 cm-1 and a broad shoulder band at around 1400cm-1 are observed in the spectra excited by the 5145 A line. The spectral profile is confirmed to depend on the excitation wavelength. A comparison of the spectral profiles between the tetrahedrally (sp3) and trigonally (sp2) bonded materials suggests that the Raman bands in the a-C films originate from carbon clusters with the sp2 configuration.

FT-IR and 1H NMR spectroscopic evidence of sugar ring conformational change in NH 4GpG on complexation to form cis-[Pt(NH 3) 2(GpG)] +

The conformational change of the ribose ring in NH 4GpG and cis-[Pt(NH 3) 2(GpG)] + was confirmed by FT-IR spectroscopic evidence as being C2′- endo, C3′- endo, anti, gg sugar ring pucker in the solid state. These results were compared with 1H NMR spectral data in aqueous solution. The FT-IR spectrum of NH 4GpG shows marker bands at 802 cm −1 and 797 cm −1 which are assigned to the C3′- endo, anti, gg sugar-phosphate vibrations of ribose (−pG) and ribose (Gp−), respectively. The FT-IR spectrum of cis-[Pt(NH 3) 2(GpG)] + (with N7N7 chelation in the GpG sequence) shows a marker band at 800 cm −1 which is assigned to the C3′- endo, and a new shoulder band at 820 cm −1 related to a C2′- endo ring pucker. The ribose conformation of (−pG) moiety in NH 4-GpG, C3′- endo, anti, gg changes into C2′- endo, anti, gg when a platinum atom is chelated to N7N7 in the GpG sequence.

Absorption spectra and micellisation of a surface-active dye in aqueous methanol solutions

The absorption spectra of aqueous methanol solutions of a surface-active dye, p-t-octylphenol yellow amine poly(ethylene oxide), have been measured at different dye concentrations, and the absorption bands are assigned to tautomeric forms of the 2′-hydroxy-4-dimethylaminoazobenzene derivative. The K band of the dye appears at 394 nm in methanol + water solutions when the dye concentration is lower than 10–5 mol dm–3. Hypochromism occurs and the shoulder band (B band) at 460–480 nm becomes manifest when the primary micelle is formed: the primary micelle is stabilised by the stacking interaction of dye molecules and the increased amount of their o-quinoid hydrazone tautomer. At higher dye concentrations the K band appears at 413 or 406 nm and its intensity increases. This step can be attributed to the second micellisation of dye molecules due to hydrophobic interaction. The methanol + 0.1 mol dm–3 HCl solutions of the dye exhibit two absorption bands (K′ and Q bands) at 320 and 528 nm, which can be assigned to the ammonium form and the resonance-stabilised azonium tautomer, respectively, of the protonated dye, when the dye concentration is dilute. Above the critical micelle concentration the absorption spectra have the K band at 405 nm, indicating that the dye is deprotonated in the micelle.

On the blue color of triiodide ions in starch and starch fractions. I. Characterization and assignment of absorption and circular dichroism spectra of triiodide ions in amylose

AbstractFour fundamental Raman lines were observed at 159, 111, 55 and 27 cm‐1 corresponding to the I bound (I) in amyloses with DP from 20 to 100, regardless of the degree of polymerization of I and the excitation wavelength. The spectral resolution was based on the molar extinction coefficient and molar ellipticity spectra of I. Eight bands, named, S1, S2, ⃛, S8 from long to short wavelength, were isolated. These were found regardless of the DP. By a resonance excitation Raman study, the characteristics of S3 and S4, comprising the shoulder around 480 nm, were found to be different from those of S1 and S2, comprising the blue band. The assignment of the spectra was based on the electronic states of the monomeric I in the exciton‐coupled dimeric unit. It was concluded that the blue band (S1,S2) belonged to the long‐axis transitions and the shoulder band (S3,S4) to the short‐axis ones on the monmeric coordinate system.

The photoinsertion of tin(II) chloride into the metal–metal bond of hexacarbonylbis(tri-n-butylphosphine)dicobalt

The photochemical insertion reaction of SnCl2 into the metal–metal bond of [P(n-C4H9)3Co(CO)3]2 has been studied in THF at 23.0 °C at the irradiating wavelengths 365 nm, 436 nm, and 546 nm. At 365 nm, the quantum yield for the reaction increases with increasing concentration of SnCl2 and approaches a limiting value of 1.0. At 436 nm, however, the quantum yield increases above 1.0 and at 546 nm, quantum yields as high as 6 were measured. The uv–visible absorption spectrum of [P(n-C4H9)3Co(CO)3]2 shows an intense band at 372 nm and a broad shoulder at about 440 nm. A simple mechanism is proposed to operate on irradiation at 365 nm due to absorption by the intense band, but a more complicated chain mechanism is suggested to operate at 546 nm as a result of absorption by the lower energy shoulder band. It appears that both mechanisms operate on irradiation at 436 nm due to the overlap of the two absorption bands at this wavelength.

Infrared studies of Se-based polynary chalcogenide glasses (I)·Y xS xSe 100−2 x(Y = Ge, As, Te)

The infrared (IR) absorption spectra for Y x S x Se 100−2 x glasses (Y = Ge, As, Te), with x = 2.5 and 5.0, are measured in the wave-number region 700-60 cm −1 at room temperature. In S x Te x Se 100−2 x glasses, the spectra are very similar to the resultant spectra which are obtained by superposing both spectra of S x Se 100− x and Se 100− x Te x glasses. This means that most of S and Te added to Se combine with Se in the forms of S 5Se 3 and Se 5Te 3 mixed rings, respectively, and the existence of STe bonds is very small. On the other hand, in As x S x Se 100−2 x glasses a strong band due to AsS bonds is found near 350 cm −1 and it is estimated that at x = 5.0, half of the added As contributes to the formation of AsS bonds. The spectra for Ge x S x Se 100−2 x glasses have complicated features. A highly intense band near 375 cm −1 due to GeS stretching vibrations and two shoulder bands near 215 cm −1 and 165 cm −1, due probably to SGeS and SGeSe bending vibrations, respectively, are found. It is indicated that considerable amounts of added Ge and S form GeS bonds.

Infrared spectra of glassy Se containing small amounts of S, Te, As, or Ge

The infrared transmission spectra of glassy Se containing 2.5 and 5.0 at % S, Te, As or Ge as well as pure Se were measured in the wavenumber region 400-60 cm −1 at room temperature. Besides the absorption bands reported already for pure Se, well-defined bands were founds at 355 cm −1 and 168 cm −1 for the addition of S, and at 205 cm −1 for Te. These new absorption bands attributed to Se 3S 5 and Se 5Te 3 mixed rings, respectively. For As, a strong absorption band appeared at 240 cm −1. The band near 135 cm −1 began to broaden and shift to lower frequency with As content. Two shoulder bands near 307 cm −1 and 278 cm −1 and a separated band at 195 cm −1 were found for Ge. With increasing Ge concentration the band at 135 cm −1 broadened and shifted to lower frequency. An interpretation for the new bands is presented on the basis of a molecular model.

Polarized absorption edge and exciton-photon interaction in phenanthrene

The width at the half-maximum and the steep exponential absorption edge of the first exciton band of phenanthrene provide experimental evidences of a strong exciton-phonon interaction in phenanthrene. Shoulder bands which locate at the exciton absorption edge are interpreted as due to the existence of lattice defects.

On shoulder bands of the U band

Two shoulder bands of the U band are theoretically investigated by computing absorption energies for optical transitions from the ground state of the U center to its high excited singlet states. The calculation is done by using the polaron model developed in a recent paper. The comparison of theoretical results with experimental results of the two shoulder bands shows that (a) one of the two shoulder bands (the U a band) arises from the optical transition to the 1 s3 p-like singlet excited state and (b) the other (the U b band) arises from the optical transitions to the 1 snp-like singlet excited states with n ⩾ 4 modified by the crystal field.

On shoulder bands of the U band

The response of ultra-lean flames, stabilised in a porous burner, to the fluctuations imposed on the fuel flow rate is investigated experimentally. The study is motivated by the likelihood of small biogas generators to produce fuels with temporal variations in their flow rate and chemical composition. The employed porous burner includes layers of silicon carbide porous foam placed inside a quartz tube. The burner is equipped with a series of axially arranged thermocouples and is imaged by a digital camera. Methane and a blend of methane and carbon dioxide (mimicking biogas) are mixed with air and then fed to the burner at equivalence ratios below 0.3. The fuel flow rate is modulated with a programmable mass flow controller by imposing a sinusoidal wave with variable amplitude and frequency on the steady fuel flow. Through analysis of the flame images and collected temperature traces, it is shown that the imposed disturbances result in motion of the flame inside the burner. Such motion is found to qualitatively follow the temporal variation in the fuel flow for both methane and biogas. Nonetheless, the amplitude of the flame oscillations for methane is found to be higher than that for biogas. Further, it is observed that exposure of the burner to the fuel fluctuations for a long time (180 s) eventually results in flame destabilisation. However, stabilised combustion was achieved for methane mixtures at amplitudes between 0 and 30% of steady values over a period of 60 s. This study reveals the strong effects of unsteady heat transfer in porous media upon the fluctuations in flame position.

Multiple chromophore species in phytochrome.

Abstract— Buffered aqueous solutions of pure phytochrome, when irradiated at 730 nm, had a main absorption band at about 660 nm and a shoulder or secondary band at 580–600 nm. When irradiated at 660 nm, these absorption bands bleached and a pair of bands at 670 and 725–730 nm appeared. When 660 nm irradiated samples were placed in the dark the 730 nm absorption slowly bleached and the 670 nm absorption band shifted to 660 nm. The kinetics of the bleaching indicated that two populations of PFR existed initially. These two populations decayed by first order kinetics with k's of 4.8 × 10‐4 sec‐1 and 3.1 × 10‐‐5 sec‐1at 25°. While the bleaching of PFR was occumng, the appearance of the 660 nm and 580–600 nm absorption bands characteristic of PR took place. The kinetics of the increase in the 580 and 660 nm absorption bands indicated that it was arising from two populations of reactants by two first order reactions with k's of 6.4 × 10‐4 sec‐1 and 3.1 × 10‐5sec‐1 at 25°. When the sodium chloride concentration of the solvent was changed the proportions of the kinetically different populations were altered. In some conditions, especially in the presence of air. reversible but non‐reciprocal changes in the four absorption bands were observed. These effects were evident after the lapse of many hours in the dark. When native phytochrome was treated with sodium dodecyl sulfate all absorption bands but the 580–600 nm absorption band were bleached and photoreversibility was lost. When native phytochrome was treated with glutaraldehyde, the 730 nm absorption band was bleached but photoreversibility was retained. It was concluded that at least four species of chromophore exist in phytochrome with absorption maxima at 580, 660, 670 and 730 nm. Each chromophore is capable of being bleached by appropriate irradiation or in the dark by chemical reactions rather than photochemical reactions. The reactions are probably coupled redox reactions between the 580–660 nm pair and the 670–730 pair of chromophores. Discrepancies observed in the reciprocity of the absorption changes in these paired bands are probably due to various degrees of uncoupling and secondarily to the redox potential of the solvent when such uncoupling occurs.

Absorption Spectra and Circular Dichroisms of Metal Complexes. I. Platinum(II)-, Palladium(II)- and Gold(III)-Complexes Containing Optically Active Diamines

Abstract In order to study the nature of absorption bands in square-planar metal complexes of d8 type, a number of platinum (II), palladium (II) and gold(III) complexes containing l-propylenediamine and l-cyclohexanediamine were prepared and their circular dichroism (CD) and rotatory dispersion (RD) as well as absorption spectra (AB) were measured. Three or four absorption bands corresponding to d–d transitions were observed for each platinum(II) and palladium(II) complex. All the complexes, except for [Au(l-pn)2]Cl3, [Au(l-chxn)2]Cl3 and [PdCl2(l-pn)], give two possitive CD bands in the wavelength region from visible to 210 mμ, which are assigned to the spin-forbidden and spin-allowed A1→E transition. Both [Au(l-pn)2]Cl3and [Au(l-chxn)2]Cl3 exhibit only one strong positive CD band corresponding to the ligand field transition probably mixed with charge transfer transition. [PdCl2(l-pn)] gives a weak negative and a strong positive band corresponding to the transitions, A1→A2 and A1→E, respectively. The CD strength of the bis-l-diamine complexes is almost twice those of the mono-l-diamine complexes. The vicinal effect of l-cyclohexanediamine was about twice as strong as that of l-propylenediamine. Absorption spectra of the [MX4]n− (M=Pt2+, Pd2+ and Au3+, X=Cl− and Br−) show a shoulder and two bands in the ultraviolet region adjacent to the ligand field bands. The shoulder band was assigned to the symmetry forbidden, and the two strong bands to the symmetry allowed pπ→dx2−y2 and pσ→dx2−y2 charge transfer transitions. In the [MBr4]n−, the pπ→dx2−y2 band splits into two components, corresponding to A1g→A1u and the other A1g→Eu transition.