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1.
Erika S. Eichmann Jennifer S. Brodbelt 《Journal of the American Society for Mass Spectrometry》1993,4(3):230-241
The reactions of dimethyl ether ions with neutral amino alcohols were examined in both a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. These ion-molecule reactions produced two types of ions: the protonated species [M+l]+ and a more complex product at [M+13]+. The abundance of the [M+13]+ ions relative to that of the [M+1]+ ions decreases with increasing formal interfunctional distance. Multistage collision-activated dissociation techniques were used to characterize the [M+13]+ product ions, their reactivities, and the mechanisms for their formation and dissociation. In addition, molecular semiempirical calculation methods were used to probe the thermochemistry of these reactions. Reaction at the amino alcohol nitrogen site is favored, and the resulting [M+13]+ addition products may cyclize for additional stabilization. Comparisons were made among the behavior of related compounds, such as alcohols, diols, amines, and diamines. The alcohols reacted only to form the protonated species, but the diols, amines, and diamines all formed significant amounts of [M+13]+ ions or related dissociation products. 相似文献
2.
The first and second moments of the transverse momentum distribution of pions ine + e ?-annihilation at fixed longitudinal momentum with respect to the jet axis are discussed, treating the hadronic final state evolving from the 2-quark system in the framework of a fireball-model. Good agreement with the published data is found. A comparison with thep T -distribution of electroproduction is made, showing qualitative agreement. This casts serious doubts on previous conclusions favoring a large partonk T inside the proton. 相似文献
3.
It is shown that local information on the imaginary part of the scattering amplitude is not sufficient for the exact evaluation of the dispersion integral. Qualitative results can be obtained in some cases depending on non local features of the imaginary part. 相似文献
4.
R. Jung S. Gerlach R. Schumann G. von Oppen U. Eichmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):415-419
We report on the first successful loading of a magneto-optical trap (MOT) with metastable He atoms from a Stark-slower. Thereby,
deceleration of the atoms relies on laser-atom interaction in an inhomogeneous electric field. We show that the results obtained
are comparable with early results from other groups achieved with a Zeeman slower. The Stark slower, which is able to fully
control the final velocity of the atomic He beam, is the first step in achieving complete spin independent kinematic control
based solely on electric fields.
Received 2 October 2002 / Received in final form 20 January 2003 Published online 29 April 2003
RID="a"
ID="a"e-mail: eichmann@mbi-berlin.de 相似文献
5.
6.
Troy N. Eichmann Timothy J. McIntyre Alexis I. Bishop Sosefo Vakata Halina Rubinsztein-Dunlop 《Shock Waves》2007,16(4-5):299-307
Flow visualization experiments were performed for supersonic and hypersonic nitrogen test gas flows over a cylinder. The results
were used to quantify the influence of three-dimensional effects on optical line-of-sight visualization measurements. Images
of cylindrical models of varying aspect ratios (length to diameter) were taken. Shock stand-off distance measurements for
the models were compared with a two-dimensional approximation and numerical simulations. For aspect ratios of two and above,
the two-dimensional approximation was acceptable within experimental uncertainty. The measured shock stand-off decreased by
less than 5% from an asymptotic value for an infinite length cylinder. For smaller aspect ratios, a correction factor for
the shock stand-off needs to be applied if comparisons between the two-dimensional approximation and experimental measurements
are to be drawn. An estimate of this correction factor has been derived from an empirical fit to the available data.
相似文献
7.
A new method to generate optical Hartley transform (OHT) for 2D real images is proposed. The method is based on polarization encoding of the coherent optical beam. Different coherent optical image processing techniques are discussed. 相似文献
8.
P. Neuling R. Neeb R. Eichmann C. Junge 《Fresenius' Journal of Analytical Chemistry》1980,302(5):375-381
Summary An analytical method was developed for measuring n-alkanes (C9 to C17) and other hydrocarbons in tropospheric air with mixing ratios of a few ppt (10–12) and higher. The hydrocarbons are collected in situ in absorption tubes, carefully protected against contamination and analysed later in the laboratory by gas chromatography. First data are reported for Atlantic air masses at the west coast of Ireland.
Qualitative und quantitative Analyse der n-Alkane C9-C17 und von Pristan in reiner Luft
Zusammenfassung Es wurde eine analytische Methode entwickelt zur Messung der n-Alkane (C9 bis C17) und anderer Kohlenwasserstoffe in reiner troposphärischer Luft mit Mischungsverhältnissen von einigen ppt (10–12) und aufwärts. Die Kohlenwasserstoffe wurden am Beobachtungsort angereichert, sorgfältig gegen Verunreinigung geschützt und später im Laboratorium gas-chromatographisch analysiert. Erste Daten für atlantische Luftmassen an der Westküste Irlands werden mitgeteilt.相似文献
9.
10.
Gernot Eichmann 《Few-Body Systems》2016,57(7):541-547
We outline a microscopic framework to calculate nucleon Compton scattering from the level of quarks and gluons within the covariant Faddeev approach. We explain the connection with hadronic expansions of the Compton scattering amplitude and discuss the obstacles in maintaining electromagnetic gauge invariance. Finally we give preliminary results for the nucleon polarizabilities. 相似文献