Nanosecond dye laser of short contructional length with a folded mirror beam expansion system

This paper reports on a nanosecond dye laser with a folded mirror beam expansion system, the output beam of which is astigmatically corrected. The overall length of the resonator is not more than 264 mm for a 50-fold meridional beam expansion. For a half-width of 5.3 ns of the nitrogen-laser pumping pulse, a bandwidth of 7 pm is achieved for a dye-laser power output of appr. 10 kW. Systems with a 30-fold or 40-fold expansion have a correspondingly larger bandwith. The investigations show that dye lasers of short constructional lengths with an internal, astigmatically corrected, low-loss mirror beam expansion system with spherical mirrors are technically realizable.     

High-order harmonic generation up to 250 eV from highly ionized argon

We demonstrate the generation of very high-order harmonics, up to 250 eV, using argon gas. This extends by 100 eV the highest harmonics previously observed using Ar and exceeds the energies observed using any other medium besides helium. This advance is made possible by using a waveguide geometry to limit plasma-induced laser beam defocusing, making it possible to generate high harmonics from Ar ions. This work shows that high harmonic emission from ions can extend laser-based coherent up-conversion into the soft x-ray region of the spectrum.     

Time-dependent quantum Monte Carlo and the stochastic quantization

We examine the relation between the recently proposed time-dependent quantum Monte Carlo (TDQMC) method and the principles of stochastic quantization. In both TDQMC and stochastic quantization, particle motion obeys stochastic guidance equations to preserve quantum equilibrium. In this way the probability density of the Monte Carlo particles corresponds to the modulus square of the many-body wave function at all times. However, in TDQMC, the motion of particles and guide waves occurs in physical space unlike in stochastic quantization where it occurs in configuration space. Hence, the practical calculation of time evolution of many-body fully correlated quantum systems becomes feasible within the TDQMC methodology. We illustrate the TDQMC technique by calculating the symmetric and antisymmetric ground state of a model one-dimensional helium atom, and the time evolution of the dipole moment when the atom is irradiated by a strong ultrashort laser pulse.     

Investigation of statistical,block and graft copolymerizations using nmr-sensitive initiators and macroinitiators

¹³C- and ³¹P-NMR studies on polymers and copolymers derived from ¹³C-enriched AIBN, ¹³C-enriched dibenzyl ketone and diphenyl-2,4,6-trimethylbenzoylphosphine oxide (Lucrin TPO) are reported. They provide information about the influence of solvent on the initiation step in copolymerization reactions, the selectivity of diphenylphosphinyl radicals and the chemical behavior of radicals derived from dibenzyl ketone. In addition, NMR, molecular weight and molecular weight distribution measurements on polymers obtained from polymerizations of methyl methacrylate conducted in the presence of stilbene indicate that stilbene or radicals derived from it may be able to moderate MMA polymerizations.     

Bifunctionalized Allenes,Part IX: An Efficient Method for Regioselective Synthesis of 4‐Heteroatom‐Functionalized Allenecarboxylates

An efficient method for regioselective synthesis of 4‐heteroatom‐functionalized allenecarboxylates by an atom economical [2,3]‐sigmatropic rearrangement of the mediated 2‐heteroatom‐functionalized alk‐3‐ynecarboxylates is described. Alkyl 4‐(dimethoxyphosphoryl), (diphenylphosphinoyl), (benzenesulfinyl), or (methanesulfonyl)‐alka‐2,3‐dienoates can be readily prepared via reactions of alkyl 2‐hydroxy‐alk‐3‐ynoates with dimethylchlorophosphite, chlorodiphenylphosphine, benzensulfanyl chloride, or methanesulfinyl chloride, respectively, in the presence of a base.     

Synthesis of 2H‐chromeno[4,3‐b]pyridine‐2,5(1H)‐diones and related heterocycles via the erlenmeyer‐ploechl reaction

1,2‐Dihydro‐5H‐[1]benzopyrano[4,3‐b]pyridine‐2,5‐diones 4a‐j were synthesized from 4‐alkylamino‐coumarin‐3‐carbaldehydes 1 and 5(4H)‐oxazolinones (azalactones) derived from N‐acetylglycine ( 2a ) and hippuric acid ( 2b ). The intermediates 3 ( 3j isolated only) underwent spontaneous recyclization via opening of the azalactone and successive formation of the fused 2‐pyridones 4 . Attempts to synthesize the selected 2H‐chromeno[3,4‐f]‐1,7‐naphthyridine 6 by Vilsmeier reaction of 4e failed. Instead, N‐deacetylation took place, followed by formylation of the amino group to the formamidine 7a . In addition, pyranopyridine 9a was obtained by condensation of the 3‐formyl‐2‐pyridone 8 with the azalactone derived from 2a and acetic anhydride.     

Zero-motion correlations in high-energy proton elastic scattering on40Ca with noneikonal nucleon-nucleon amplitude

Using a noneikonal expression for the two-body scattering amplitude, consistent with the proton-nucleon scattering data, the cross-section of the 1.04 GeV-proton elastic scattering on⁴⁰Ca is calculated by the Glauber-Sitenko theoretical scheme in the framework of the coherent density fluctuation model (CDFM) as well as of the independent-particle model (IPM). It is shown that the use of the noneikonal amplitude in the CDFM calculation improves the agreement with the experimental data especially at larger scattering angles in contrast to the case of the independent-particle model. To that end a decisive role play the zero-motion flucton correlations taken into account in the CDFM.