Frequency doubling of Nd:YAG- and GaAs-lasers by KNbO3: Ta crystals

Abstract

For KNb_1-xTa_xO₃ crystals the influence of the Ta-concentration on the phase-matching properties for optical second harmonic generation (SHG) was measured. For non-critical phase matched SHG of the Nd:YAG-laser (1064nm) the coefficient d₃₁ of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d₃₂ was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Non-critical phase-matching at room temperature can be reached with the GaAs-laser for a Ta-concentration of ≈9%. The corresponding value for the Nd:YAG-laser is ≈14%.     

Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]carbazoles

The DIBAL‐H promoted reductive pyran ring opening of dialkylpyrano[3,2‐a]carbazoles provides a direct access to a broad range of prenyl‐ and geranyl‐substituted carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila‐E, 7‐hydroxyheptaphylline, 7‐methoxyheptaphylline, mukoenine‐B (clausenatine‐A), mukoenine‐A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine‐A, and isomurrayafoline‐B.     

Magnetism under high pressure studied by 57Fe and 151Eu nuclear scattering of synchrotron radiation

The nuclear forward scattering (NFS) of synchrotron radiation is especially suited for probing magnetism at very high pressure, here in the Mbar range, by the nuclear resonances of ⁵⁷Fe and ¹⁵¹Eu. We report on high pressure (h.p.) NFS studies with the 14.4 keV transition of ⁵7Fe on magnetic RFe₂ Laves phases of cubic C15 structure (YFe₂, GdFe₂) and hexagonal C14 structure (ScFe₂, TiFe₂) at pressures up to 100 GPa (=1 Mbar). We present also h.p. NFS studies performed with the 21.5 keV resonance of ¹⁵¹Eu, probing the magnetism in the CsCl-type h.p. phase of EuTe. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthese makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung

Synthesis of Macrocyclic Lactones by Ring Enlargement Reaction Treatment of 3-(1-nitro-2-oxocyclohexyl)propanal ( 1 ) prepared by Michael addition of 2-nitrocyclohexanon and acrylaldehyde with methyltri (2-propoxy)tita-nium yielded a mixture of 2 and 3 which was converted into 6-nitro-9-decanolide ( 4 ).     

A simple expression for the buffer index of a weak polyprotic acid

A simple expression for the buffer index of a solution containing a weak polyprotic acid is derived and presented.