Automatically tunable continuous-wave optical parametric oscillator for high-resolution spectroscopy and sensitive trace-gas detection

We present a high-power (2.75 W), broadly tunable (2.75–3.83 μm) continuous-wave optical parametric oscillator based on MgO-doped periodically poled lithium niobate. Automated tuning of the pump laser, etalon and crystal temperature results in a continuous wavelength coverage up to 450 cm^-1 per poling period at <5×10^-4 cm^-1 resolution. The versatility of the optical parametric oscillator as a coherent light source in trace-gas detection is demonstrated with photoacoustic and cavity ring-down spectroscopy. A 17-cm^-1-wide CO₂ spectrum at 2.8 μm and multi-component gas mixtures of methane, ethane and water in human breath were measured using photoacoustics. Methane (at 3.2 μm) and ethane (at 3.3 μm) were detected using cavity ring-down spectroscopy with detection limits of 0.16 and 0.07 parts per billion by volume, respectively. A recording of ¹²CH₄ and ¹³CH₄ isotopes of methane shows the ability to detect both species simultaneously at similar sensitivities. PACS 42.65.Yj; 42.72.Ai; 42.62.Fi     

Molecular and cluster structures in 18O

We have studied the multi-nucleon transfer reaction ¹²C ( ⁷Li ,p) at E _lab = 44 MeV, populating states in the oxygen isotope ¹⁸O . The experiments were performed at the Tandem accelerator of the Maier-Leibniz Laboratory in Munich using the high-resolution Q3D magnetic spectrograph. States were populated up to an excitation energy of 21.2MeV with an overall energy resolution of 45keV, and 30 new states of ¹⁸O have been identified. The structure of the rotational bands observed is discussed in terms of cluster bands with the underlying cluster structures: ¹⁴C$ $\displaystyle \otimes$ $\displaystyle \alpha$ $and 12C ? 2n ? $ \alpha$ . Because of the broken intrinsic reflection symmetry in these structures the corresponding rotational bands appear as parity doublets.     

On investigation of high Tc superconductors with Electron Paramagnetic Resonance spectrometers

Following the discovery of high T_c superconductors, many researchers have applied EPR spectrometers to investigate their properties using the regular instructions to operate the spectrometer. As no substantial information was obtained it was soon practically abandoned. Investigations performed recently with the EPR technique, using a different operating method than the conventional one and the introduction of a detailed theoretical study related to the interaction of the JV with the microwave magnetic field lead to new and important results related to properties of high anisotropy superconductors indicating that the EPR spectrometer can be used to investigate properties of high anisotropy superconductors. The failures when using conventional operating method to obtain meaningful results and the method used in the present work to carry out the measurements in a proper manner are presented. Some important results obtained in investigating high anisotropy superconductors by the EPR technique are presented.     

Biosynthesis of digitoxose in Digitalis lanata EHRH. (Preliminary experiment). Deoxysugar. 39

Strongly radioactive digitoxin ( 6 ) could be isolated (without dilution) in crystalline form from young plants of Digitalis lanata after their inoculation with D-Glucose-[6-¹⁴C] using the wick method. Hydrolytic cleavage of this digitoxin gave digitoxigenin ( 11 ) and D-digitoxose ( 7 ), both being isolated in crystalline form (without dilution). The genin was found to be 4 times more active, pro mole, than the digitoxose. This can be best explained when one assumes that the plant converts 1 mole of D-glucose into 3 moles of acetic acid. After degradation of the digitoxose using NaJO₄, acetaldehyde (as the crystalline p-nitrophenylhydrazone) and formic acid (as the Pb salt) could be isolated. The acetaldehyde carried 65% and the formic acid 8,45% of the activity of the digitoxose. This is compatible with the assumption that digitoxose is formed in the plant from D-glucose without re-arrangement of the carbon chain. The appreciable activity of the formic acid could be derived from the relatively large proportion of radioactivity lost (ca. 38,9%), partly in the form of C₁-subunits, in the transformation of the intermediary lanosterol into digitoxigenin. This lost activity may be incorporated in unspecifically labelled D-glucose which then re-enters the biosynthetic pathway.     

Die Struktur des Harpagosids. 2. Mitteilung über Iridoide

The structure and configuration of harpagoside, a bitter principle from the roots of Harpagophytum procumbens DC, have been elucidated by degradation reactions and NMR. spectra. The hitherto uncertain position of a secondary hydroxyl group could be assigned to C-6 of the aglycone moiety. As earlier postulated, harpagoside ( 1 ) as well as its saponification product, harpagide ( 12 ), belong to a series of natural enol ethers known as iridoids.     

Detection of fragment genesis in the mass spectrometer. III. Analysis of amino-acid sequence in oligopeptides and in mixtures of oligopeptides by DADI-mass spectrometry (author's transl)]

Detection of Fragment Genesis in the Mass Spectrometer. III. Analysis of Amino-Acid Sequence in Oligopeptides and in Mixtures of Oligopeptides by DADI-Mass Spectrometry. The amino acid sequence was analysed by DADI mass spectrometry in simple oligopeptides and in mixtures containing two or three peptides.     

Orientational aspect of transient absorption in solutions

In picosecond spectroscopy transient absorption methods are utilized to measure ground-state repopulation kinetics. Since linearly polarized light pulses from mode-locked lasers are used, the transient absorption characteristics in solutions are governed by the rotational diffusion of the absorbing molecules, too. The theory for isotropic diffusion is given and compared to a measurement on the rhodamine 6G molecule dissolved in solvents of different viscosity using a novel pulse spectrophotometer.     

Piperaceae alkaloids: Part IV. Structure and Synthesis of Cyclostachine A,Cyclostachine B and Cyclopiperstachine

Three new alkaloids designated as cyclostachine A (2), cyclostachine B (7) and cyclopiperstachine (10) have been isolated from Piper trichostachyon C. DC. Their structures have been derived on the basis of spectral and degradative studies and confirmed by synthesis. The ¹H- and ¹³C-NMR. spectra of these compounds are discussed.