Search results for "induced"

Kinetische untersuchungen zur strahleninduzierten festkörperpolymerisation von trioxan und tetroxan IV. Mitt. der Reihe “kinetische und morphologisch…

1971

Die strahlungsinduzierte Polymerisation von kristallinem Tetroxan und Trioxan wurde untersucht und der Einflus von Strahlendosis, Reaktionszeit und -temperatur auf den Umsatz und das Molekulargewicht der entstehenden POM, insbesondere bei der Nachpolymerisation, studiert. Die Zeit-Umsatz-Kurven fur die Nachpolymerisation laufen bei beiden Monomeren asymptotisch gegen einem Grenzwert des Umsatzes, der mit steigender Reaktionstemperatur ansteigt. Die Aktivierungsenergie der Nachpolymerisation wurde zu 24 ± 2 kcal/Mol fur Tetroxan und zu 36–38 kcal/Mol fur Trioxan bestimmt. Die Zeit(t)-Umsatz(x)-Kurven fur Tetroxan lassen sich durch die empirische Gleichung: beschreiben, wobei k1 und k2 Konsta…

<title>Time-resolved fluorescence study of interaction of the monoclonal anticoproporphyrin antibodies and (Pt-)coproporphyrin</title>

1995

Mechanisms of ligand binding by monoclonal anti-coproporphyrin antibodies are studied by steady-state and time-resolved fluorescence spectroscopy by use of a picosecond laser system. The antibodies quench the coproporphyrin (CP) fluorescence, but the CP fluorescence spectra show a strong shift of maxima at high concentrations of antibodies (Ab) or their Fab fragment. This can be explained by a special type of Ab or Fab dimerization. Fluorescence decays of CP are measured at different concentrations of Ab and different pH values. The following deconvolution procedure based on the non-linear least squares method reveals a two- exponential character of the fluorescence decay. Data obtained by …

Temperature measurement in gas mixtures by femtosecond Raman-induced polarization spectroscopy

2003

The potential of femtosecond Raman-induced polarization spectroscopy (RIPS) for the simultaneous determination of temperature and concentrations was investigated. These measurements were related to the rotational time response of the molecular gas mixture, which was measured as a function of the pump-probe time delay. The change of the polarizability anisotropy with respect to the vibrational levels was taken into account. The results of temperature measurements in pure CO2 showed good agreement with the values obtained by a thermocouple. The RIPS technique was also applied to a CO2-N2 gas mixture to determine simultaneously temperatures and concentrations at temperatures up to 600 K. The a…

High resolution spectroscopy and potential determination of the (3)1Pi state of NaCs.

2006

The (3)(1)Pi state of the NaCs molecule was studied by high resolution Fourier-transform spectroscopy. The (3)(1)Pi--X (1)Sigma(+) laser induced fluorescence was excited by an Ar(+) ion laser or by a single-mode frequency-doubled cw Nd:YAG laser. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the (3)(1)Pi state term values, as well as to observe Lambda splittings in a wide range of vibrational (v(')) and rotational (J(')) quantum numbers. The data field includes about 820 energy levels of (3)(1)Pi NaCs in the range from v(')=0 to 37 and from J(')=3 to 190, which corresponds to ca. 95% of the potential well depth. Direct fit o…

Double Laser LIBS and micro-XRF spectroscopy applied to characterize materials coming from the Greek-Roman theater of Taormina

2009

The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown, in recent years, its great potential for rapid qualitative analysis of materials. The possibility to implement a portable instrument that perform LIBS analysis makes this technique particularly useful for in situ analysis in the field of cultural heritages. The aim of this work is to compare the results, obtained by LIBS measurements with X-Ray Fluorescence (XRF) ones, on calcareous and refractory materials coming from the Greek-Roman theater of Taormina. Calibration curves for LIBS and XRF were obtained by measuring certified reference materials and using them as standards. LIBS measurements we…

Acute and short-term toxicity of 2,3,4,6-tetrachlorophenol in rats

1981

Molecular structure of p -methylaniline and its van der Waals complexes with CF 3 H, CH 4 and CF 4 studied by laser induced fluorescence spectroscopy…

2002

The UV fluorescence excitation and dispersed fluorescence spectra of jet-cooled p-methylaniline have been obtained for the S1←S0 transition. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes and with the help of computed vibrational frequencies. The structure of p-methylaniline in both the S0 and S1 states has been studied at ab initio quantum chemical calculations at MP2 and CIS levels of theory using the 6-31+G∗ basis sets. Both low- and high-resolution laser induced fluorescence spectra of p-methylaniline van der Waals complexes with CF3H, CH4 and CF4 have been characterised following jet-expansion investigations. The equilibrium g…

Long lived photoinduced charges in donor-acceptor anthraquinone substituted thiophene copolymers

2006

The photoinduced charge-transfer properties of a series of polyalkylthiophene copolymers, carrying anthraquinone substituents covalently linked to the conjugated backbone, have been studied in the solid state by photoinduced absorption (PA) and light-induced electron spin resonance (LESR) spectroscopy. The measurements indicate the formation of metastable charges arising from the photoinduced electron transfer from the polythiophene backbone to the anthraquinone moieties. At low temperatures (below 200 K), long-lived persistent charges are formed, exhibiting lifetimes that extend for several minutes; their recombination kinetics has been studied by following the formation and decay of the P…

Formation of HXeO in a xenon matrix: Indirect evidence of production, trapping, and mobility of XeO (1 1Σ+) in solid Xe

2004

IR spectroscopy, laser induced fluorescence (LIF), and thermoluminescence (TL) measurements have been combined to monitor trapping, thermal mobility, and reactions of oxygen atoms in solid xenon. HXeO and O(3) have been used as IR active species that probe the reactions of oxygen atoms. N(2)O and H(2)O have been used as precursors for oxygen atoms by photolysis at 193 nm. Upon annealing of matrices after photolysis, ozone forms at two different temperatures: at 18-24 K from close O ...O(2) pairs and at approximately 27 K due to global mobility of oxygen atoms. HXeO forms at approximately 30 K reliably at higher temperature than ozone. Both LIF and TL show activation of oxygen atoms around 3…

Coupling between the Thermal Evolution of the Heme Pocket and the External Matrix Structure in Trehalose Coated Carboxymyoglobin

2003

Proteins can assume a very large number of conformations (conformational substates), all concurring to its function. We present experimental evidence for the existence, in trehalose coated carboxymyoglobin, of a structured environment of the protein, tightly coupled to the heme pocket structure, as experienced by the bound CO molecule. This was evidenced by the strict correlation observed between the thermal evolution (300−20 K) of the CO stretching and of the water association bands in samples of carboxymyoglobin embedded in trehalose matrixes of different hydration. This observation put forward the coupling between the degrees of freedom of the matrix and those of the protein. In the drie…