Scanning tunneling lithography of silicon nanoparticle films

Monolayer and bi-layer silicon nanoparticle (SiNP) films with wide band gaps (up to 4 eV) have been produced in UHV with narrow size distributions of particles with 2-4 nm diameters and were studied using scanning tunneling microscopy (STM) and spectroscopy (STS). The films then were manipulated by applying different values for the tunneling resistance. Nanoparticle fusion and fission processes allow to shape the particles in the films in various ways and to write in white and black on the film template.     

Rapid communicationPhotoelectron emission in femtosecond laser assisted scanning tunneling microscopy

Direct illumination of the tunneling gap in an ultrahigh vacuum scanning tunneling microscope with ultrashort pump-probe laser pulses may offer ultimate spatial and temporal resolution in surface experiments. The electronic bandwidth of the tunneling gap ( 1 THz) does not limit the time resolution. Our experiments show that multiphoton photoelectron emission from the sample limits the application of this detection scheme at high laser fluence. However, a substrate specific pump-probe effect in the photoelectron yield with femtosecond transients is observed on Tantalum and on GaAs(110) surfaces. Received: 5 November 1996     

The ν5 perpendicular band of deuterated fluoroform

The results of an infrared diode-laser-heterodyne investigation of the ν₅ band of deuterated fluoroform (CDF₃) are presented. Infrared heterodyne measurements (410), together with the previously obtained 88 infrared laser-Stark measurements, 12 infrared-radiofrequency, two-photon measurements, 8 microwave measurements, and 22 submillimeter-wave heterodyne measurements were analyzed by linear least-squares fitting of the data with a 43-constant linear Hamiltonian. Most of the ground-state and ν₅-state constants are obtained to very high accuracy, and the fit to the data is excellent. Examination of the data reveals effects such as A₊-A_? splittings and perturbation-allowed transitions arising from the mixing of kl = 1 and kl = ?2 levels in the ν₅ state due to (±2, ±1) interactions.     

Trennung von racemischen Alkylaminos?uren durch HPLC mit chiraler mobiler Phase

Zusammenfassung Die Trennung der Alkylaminosäuren mit 4 bis 6 Kohlenstoffatomen gelingt in einfacher Weise an einer Umkehrphase durch HPLC mit chiralem wäßrigen Eluens. Der Eluent enthält einen chiralen Kupfer(II)-Komplex mit L-Aspartyl-L-phenylalaninmethylester in einer Konzentration von 1 mMol/l. Es lassen sich auch Gemische einiger Alkylaminosäureenantiomere auftrennen.

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Separation of racemic alkylamino acids with HPLC using a chiral mobile phase

Summary The separation of alkylamino acids containing 4 to 6 carbon atoms is possible with simple reversed phase HPLC using chiral aqueous eluant. The eluant contains a chiral copper(II) complex of L-aspartyl-L-phenylalanine methyl ester in a concentration of 1 mMol/l. The separation of mixtures of some alkylamino acids enantiomers is also possible.

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D26: Teil der Dissertation U. Wagenbach, Universität Giessen

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Dem Fond der Chemie danken wir für die Unterstützung der Arbeit.     

Magnetic proximity effect in EuO-Cs interface

In the surface of the ferromagnetic insulator EuO is covered with a small amount of cesium, the photoelectric magnetization curves P(H) show magnetic saturation in contrast to those of the pure surface. The proximity of the Cs film causes the paramagnetism of the clean EuO surface to disappear.     

Pressure broadening of OCS in the 10μm region

We report diode laser heterodyne measurements of pressure-broadening coefficients of OCS in the 020°–00°0 vibrational band of OCS and compare these measurements and previously reported microwave measurements with calculations performed with a recent cutoff-free impact technique.     

Heterodyne frequency measurements on carbonyl sulfide near 1050 cm

Heterodyne techniques have been used to measure the frequency differences between carbonyl sulfide (OCS) absorption lines and CO₂ laser transitions. A tunable diode laser was used both to scan the OCS absorption spectrum and to provide a beat signal against a CO₂ laser. Frequency differences as great as 8.6 GHz were measured. Many different OCS hot-band transitions were measured near 1050 cm⁻¹, and the measurements on the 02⁰0-00⁰0 band have been extended to such high J levels (J′ = 86) that higher-order centrifugal distortion terms are needed to fit the data.