Fourier Transform Spectroscopy of theYΣ–XΠiTransition of CuO

TheY²Σ⁺–X²Π_inear-infrared electronic transition of CuO was observed at high resolution for the first time. The spectrum was recorded with the Fourier transform spectrometer associated with the McMath–Pierce Solar Telescope at Kitt Peak. The excited CuO molecules were produced in a low pressure copper hollow cathode sputter with a slow flow of oxygen. Constants for theY²Σ⁺states of CuO are:T₀= 7715.47765(54) cm⁻¹,B= 0.4735780(28) cm⁻¹,D= 0.822(12) × 10⁻⁶cm⁻¹,H= 0.46(10) × 10⁻¹⁰cm⁻¹, γ = −0.089587(42) cm⁻¹, γ_D= 0.1272(79) × 10⁻⁶cm⁻¹,b_F= 0.12347(22) cm⁻¹, andc= 0.0550(74) cm⁻¹. ImprovedX²Π_iconstants are also presented.     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.     

Fourier transform spectroscopy of the AΠ-XΣ transition of NH

The A³Π-X³Σ⁻ transition of NH has been observed using a high-resolution Fourier transform spectrometer. The first three vibrational levels in each state were observed and the vibrational, fine structure, and rotational constants obtained.     

7,8-Dihydropyrido[2,3-d]pyrimidin-2-one; a bicyclic cytosine analogue capable of enhanced stabilisation of DNA duplexes

Incorporation of a bicyclic cytosine analogue, 3-beta-D-(2'-deoxyribofuranosyl)-7,8-dihydropyrido[2,3-d]pyrimidine, into synthetic DNA duplexes results in a greatly enhanced thermal stability (3-4 degrees C per modification) compared to the corresponding unmodified duplex.     

Direct sample fraction deposition using electrospray in narrow-bore size-exclusion chromatography/matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for polymer characterization

A direct sample fraction deposition method was developed for off-line size-exclusion chromatography (SEC)/matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. By using electrospray, the SEC eluent, together with a suitable matrix solution added coaxially, was directly deposited on the MALDI plate. Owing to the formation of very small droplets in electrospray, solvent evaporation is much faster. The fractionation volume in narrow-bore SEC, which can directly be collected in one MALDI spot, can easily be optimized in the range of a few microlitres. In addition, fairly homogeneous sample spots were obtained. The possible influence of composition variation of the SEC effluent on the analytical results using direct fraction deposition was investigated; no substantial effects were observed. The applicability of the method was demonstrated by characterizing a broad poly(methyl methacrylate) sample. Copyright 2000 John Wiley & Sons, Ltd.     

Determination of ketoprofen in plasma using high-performance liquid chromatography. Comparison with gas--liquid chromatography (author's transl)

A new method of determination of ketoprofen 2-(3-benzoyl phenyl) propionic acid in plasma using high-performance liquid chromatography (HPLC) is described. After extraction by diethyl either in acidic medium, ketoprofen and the internal standard, 2-(4-benzoyl phenyl) butyric acid, are methylated with gaseous diazomethane and their concentrations measured by HPLC using in LiChrosorb Si 60 (5 micrometer) column and dichloromethane-hexane (60:40) as the mobile phase. The absolute retention times of the internal standard and ketoprofen are 11.6 and 12.8 min, respectively. The precision of the methods is +/- 4% and the lower detection limit ranges from 0.06 to 0.10 microgram/ml. The results obtained by HPLC show a very good correlation with those obtained by gas--liquid chromatography. The proposed method is sensitive, reproducible and rapid and very suitable for ketoprofen determination in pharmacokinetic studies.