After effects of β− on time differential perturbed angular correlation spectra

The after effects of β⁻ -decay on time differential perturbed angular correlation (TDPAC) spectra of II–VI semiconductor CdS have been studied using β⁻ -emitting¹¹¹Ag as well as^111mCd as probe nuclei. The TDPAC spectrum of¹¹¹Ag in CdS exhibits a time dependent interaction indicating that the preceding β⁻ -decay leaves the daughter nucleus in an excited state. The recovery time (τ_g) of the probe atom was found to be 16±6 ns while Abragam and Pound's relaxation time (τ_kr) was found to be 9±2 ns. The results show that β⁻ -decay does change the chemical environment around the probe atom.     

Infra-red and Raman spectra of N-methyl-N′-n-alkylthioureas

The i.r. and Raman spectra of solid CH₃NHCSNH(CH₂)nCH₃ (n = 0–15) MTUR′ and CH₃NDCSND(CH₂)nCH₃ (n = 0–9) MTUR′-d₂ are examined. The vibrational properties of N,N′-disubstituted thioureas are studied on the basis of the spectral comparison among the series of compounds, of the wavenumber shift by N-deuteration and of a comparison with the vibrational properties of urea analogue, MUR′. From the analysis of interactions between end-group vibrations and methylene band progression modes it is concluded that MTUR′ molecules are in a skeletal planar structure with an extended n-alkyl chain.     

On the extraction of spectra of components from spectra of mixtures. A development in factor theory—II

The theory of factor analysis developed in Part I [A. Muller and D. Steele, Spectrochim. Acta 46A, 817 (1990) [1] is extended to cases where m > 3, m being the number of factors. The effect of increasing the number of independent parameters by m(m-1) for T′ and the subsequent changes produced in the transformed eigenspectra, are investigated. Applications to actual spectra of mixtures of: (A) butan-2-one, ethyl ethanoate, cyclohexane and oct-1-ene (B) butan-2-one, ethyl ethanoate, cyclohexane and 2-methylpentane and (C) oct-1-ene, butan-2-one, ethyl ethanoate, cyclohexane and 2-methyl-pentane are presented. Using standard target techniques, an alternative approach is developed for the m> 3 case. This is based on transformation of the leading three eigenspectra, followed by identification and elimination of a component in a repetitive manner, until completion. The problems associated with the implementation of the Beer-Lambert Law are explored the need for accurate determination of a suitable wavenumber block to ensure the removal of the correct amount of each component, is examined. The ability to recognize at least one of the m component spectra per programme cycle is demonstrated.     

On the extraction of spectra of components from spectra of mixtures. A development in factor theory—I

The theory of factor analysis is extended to permit the computer based extraction of the spectra of pure components from spectra of mixtures. A simultaneous linear, non-orthogonal transformation of the eigenspectra and eigenvectors is used to generate all positive absorbances and concentrations within noise level. Applications to actual spectra of mixtures of: (A) ethyl ethanoate, butan-2-one and oct-1-ene; (B) ethyl ethanoate, butan-2-one and cyclohexane; and (C) butan-2-one, cyclohexane and 2-methylpentane are presented. The effects of changes in signs of the constrained diagonal elements of the transformation matrix is investigated. To explore the ability of the software to cope with component spectra in which there are no wavenumbers at which one component dominates an artificial set of mixtures is examined. Recognizable spectra are extracted. It appears that, even when there are no wavenumbers at which one component dominates, the condition of finding “the sum of squares of negative absorbances/concentrations” near zero is adequate to yield useful spectra for library searches.     

Study on the resonance Rayleigh scattering spectra and resonance non-linear spectra of congo red-amikacin system and its analytical application

The interaction between congo red (CR) and amikacin (AMK) was studied by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS) and second-order scattering (SOS) combining with absorption spectrum. In a weak acidic medium, CR combined with AMK to form an ion association complex with the composition ratio of 1∶1 by electrostatic interaction, hydrophobicity and charge transferring effect. As a result, the new spectra of RRS, FDS, and SOS appeared and their intensities were enhanced greatly. The maximum wavelengths of RRS, FDS and SOS were located at 563 nm, 475 nm and 940 nm, and the scattering intensities were proportional to the concentration of AMK. These three methods have very high sensitivities, and the detection limits were 4.0 ng·mL?1 for RRS, 3.6 ng·mL?1 for FDS and 1.9 ng·mL?1 for SOS, respectively. At the same time, the methods have better selectivity. A new method for the determination of trace amounts of AMK with congo red by resonance scattering technique has been developed. The recovery for the determination of AMK in blood serum and urine sample was between 95.5% and 105.5%. In this study, the properties, such as enthalpy of formation, charge distribution and mean polarizability, were calculated by AM1 quantum chemistry method. In addition, the reaction mechanism and the reasons for the enhancement of scattering spectra were discussed.     

Infra-red spectra of α-CrPO4-type phases

Infra-red spectra of polycrystalline samples of α-CrPO₄, RhPO₄ and CrAsO₄, the only known phases belonging to the α-CrPO₄ structural type, were recorded and briefly discussed with the aid of a factor group analysis.     

Vibrational Raman spectra of AgIAgPO3 glasses

Raman spectra of fast ion conducting AgIAgPO₃ glasses have been investigated as a function of composition and temperature. Only an average anionic environment is indicated for Ag⁺ ions. The spectroscopic variations have been found to be consistent with the model of structural unpinning proposed earlier by the authors.     

Triplet—triplet absorption and polarization spectra of phenazine

Employing laser photoselection spectroscopy, the triplet—triplet (T—T) polarization spectrum over the visible portion of the spectrum of phenazine was recorded. The strong T—T absorption band located in the violet portion of the spectrum is differently polarized from the flat band stretching from the blue to the red portion of the spectrum. This indicates the presence of two electronic transitions. The portion located in the violet spectral region is long-axis-polarized and presents the ³B⁻_3g ← ³B⁺_2u transition and the long-wavelength portion to the short-axis-polarized ³A⁻_1g ← ³B⁺_2u transition.     

Hamiltonian for rovibrational spectra of “hot” molecules

A variational method based on the determination of rotation as a state with a constant angular momentum has been proposed for calculating rovibrational energy levels of a polyatomic molecule. By using this method, energy level values can be determined for any vibrational state with arbitrary values of vibrational quantum numbers. This makes it possible to calculate the rovibrational energy levels of the “hot” molecules.     

Unifit 2002—universal analysis software for photoelectron spectra

The current level of development of the spectra analysis software Unifit for Windows is presented and evaluated by checking with test spectra. The program is characterized and the correctness of the numerical routines is demonstrated for the particular cases of the Shirley type background model and the Gaussian-Lorentzian product model functions. Different approaches to an optimum fit result are suggested. A convenient analysis of the assessment of the peak fit procedure is proposed. All results are presented in tabular form too, to make the data more comprehensible.     

Host�Cguest association studied by fluorescence correlation spectroscopy

Fluorescence Correlation Spectroscopy (FCS) is a powerful single molecule technique for the study of the stability and the association dynamics of supramolecular systems and, in particular, of host?Cguest inclusion complexes. With FCS the host?Cguest binding equilibrium constant is determined analysing the variation in the diffusion coefficient of the fluorescent guest or host with no need for a change in the photophysical properties of the fluorescent probe. FCS gives also access to the association/dissociation rate constants of the host?Cguest inclusion providing that the fluorescence intensity of host or guest changes upon complexation. These rate constants can be compared with that of a diffusion-controlled process estimated from the same FCS experiment allowing for a better understanding of the association dynamics. The results show that cyclodextrin cavities act as ??hard?? cages which put geometric and orientational restrictions on the inclusion of a hydrophobic guest, whereas micelles behave as ??soft?? cages without geometrical requirements. In our contribution to this special issue we review briefly the application of FCS to the study of host?Cguest inclusion complexes with an emphasis on practical aspects and relevant bibliographic references.     

SDAT implementation for the analysis of radioxenon β–γ coincidence spectra

The standard deconvolution analysis tool (SDAT) was developed for analysis of radioxenon β–γ coincidence spectra measured as part of the international monitoring system as defined in the comprehensive nuclear-test-ban treaty. The SDAT software analyzes each β–γ coincidence spectrum by fitting library vectors of each radionuclide of interest: ^131mXe, ^133mXe, ¹³³Xe, and ¹³⁵Xe. Detector background and radon are incorporated as optional components of the sample solution. Results are reported in mBq m^?3. A new graphical user interface has been developed to facilitate ease of use and improve the data visualization. Automated energy versus channel calibration algorithms were developed and implemented based on ¹³⁷Cs β–γ coincidence spectra. Details on the user tool and testing are included.     

Vibrational spectra of X2O7n− anions

A careful study of the Raman spectra of aqueous solutions containing X₂O₇ⁿ⁻ anions, where X = P, n = 4; X = Cr or Se, n = 2, has shown for the first time that in all cases the δX-O-X bending mode occurs below 100 cm⁻¹. In addition, further information on the XO₃ terminal stretches was obtained from FTIR spectra of the aqueous solutions. Consequently, more realistic vibrational assignments were obtained for these frequently-studied inorganic anions.     

Photoacoustic spectra of some biologically active metal chelates—II

The visible absorption spectra of 5-(p-sulphon atophenyl)-1,3,4-oxadiazole-2-thione (ligand) and the metal chelates derived from Mn(II), Co(II), Ni(II) and Zn(II) salts have been recorded, in the powder form, on a single beam photoacoustic spectrometer. The photoacoustic spectra give information about charge transfer and d-d transitions that could not be observed in their optical u.v.-vis spectra.