摘要:

AbstractApplication of a laser ion source (LIS) is a promising new technique for trace analysis with high efficiency and selectivity. One of the problems which can limit its efficiency attained in practice is the adsorption of sample atoms on the hot walls of the LIS cavity. We have studied the release of atomic technetium from different wall materials at temperatures up to 2500 K. For these investigations resonance ionization of technetium atoms applying a copper vapour pumped dye laser system and γ‐spectrometry of 6‐h99mTc have been used. Theoretical calculations of the heat of desorption for technetium on different wall materials are presented and compared with experimental data. Though the results reported concern technetium, most of the considerations are quite general for a laser ion so

ISSN:0003-3804    

DOI:10.1002/andp.19915030102

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA synchroneously pumped mode‐locked cavity‐dumped dye laser, which delivers nearly Fourier‐limited output pulses with 20 W peak power, 500 ps pulsewidth and 1.5 GHz spectral bandwidth is used to populate selected rovibronic levels in excited electronic states of alkali molecules. The laser induced fluorescence is filtered through a monochromator and the lifetimes of individual rovibronic levels are determined with the single photon delayed coincidence technique. The influence of different perturbations on the lifetimes is investigated and disc

ISSN:0003-3804    

DOI:10.1002/andp.19915030103

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractWir führen eine Reihe von elementaren optischen Experimenten mit einem nichtklassischen Lichtfeld durch, das über parametrische Fluoreszenz erzeugt wird und die Besonderheit aufweist, daß die Photonen ausschließlich paarweise auftreten. Beim Auftreffen auf einen verlustfreien, teildurchlässigen Spiegel werden die Photonen eines Paares gemäß einer Binomialverteilung auf das reflektierte und das transmittierte Bündel verteilt. Dieses Ergebnis ist unabhängig vom Kohärenzgrad. Die beobachtete Invarianz der Verteilung kann auf eine Balance zwischen quantenmechanischen Stimulations‐ und Interferenzeffekten in den Ein‐ und Ausgangsarmen des Strahlteilers zurückgeführt werden. Beim zweimaligen Durchlaufen eines Strahlteilers in einem Michelson‐Interferometer treten Interferenzen zwischen den verschiedenen möglichen Zweiphotonenzuständen im Interferometer auf. Das Korrelations‐Interferogramm für Photonenpaare besitzt eine höhere Auflösung als das Intensitäts‐Interferogramm für die Transmission einzelner Photonen. Wir deuten dieses Verhalten als quantenmechanische Interferenz zwischen der größeren Zahl von Möglichkeiten, die ein Photonenpaar im Vergleich zu einzelnen Photonen hat, das Interferometer zu durchlaufen. Die Anwendung dieser Überlegungen auf Lichtfelder mit Paaren von Photonen unterschiedlicher Energie führt zu Korrelations‐Interferogrammen, die deutlich von den mit klassischen Feldern aufge

ISSN:0003-3804    

DOI:10.1002/andp.19915030104

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe ground‐state hyperfine transition ΔmF= 0 of trapped Yb+ions has been measured as 12642812119.6 (0.4) Hz. The frequency instability of a microwave, controlled by this resonance, is characterised by the standard deviation 2·10−11· (τ/sec)−1/2, where τ is the time separation of probes. The performance of this frequency standard or “clock” exceeds the stability of commercial cesium clocks and still offers major potential f

ISSN:0003-3804    

DOI:10.1002/andp.19915030105

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractAlternatively to path integrals quantum fields can be characterized by functional equations. Weak mappings of quantum fields are defined by mappings between such functional equations. This is exemplified for a regularized nonlinear spinor field theory and a boson theory of bound states. A corresponding weak mapping theorem is derived. In the appendix strong mappings, i.e. operator mappings are critically discussed.

ISSN:0003-3804    

DOI:10.1002/andp.19915030106

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractA semiclassical theory for heavy ion scattering in the Fresnel diffraction regime covering coupled elastic and inelastic channels is developed. The scattering is described as diffraction off the rainbow trajectory along which the development of the internal degrees of freedom is calculated. Simple formulae for the transition amplitudes are derived and interpreted in terms of matching conditions, time scales and potential strengths at closest approach. Polarization potentials comprising of real and absorptive terms and of tensors of various ranks are constructed. Analyzing power data for elastic and inelastic scattering of polarized7Li on120Sn are analyzed.

ISSN:0003-3804    

DOI:10.1002/andp.19915030107

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractWe present the results of numerical experiments in which electron‐atom scattering occurs in the presence of a strong laser field. We compare our results for both forward and backward scattering with previous theoretical work in both strong‐field and weak‐field re

ISSN:0003-3804    

DOI:10.1002/andp.19915030108

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractSynergetic computers are a new class of highly parallel computers which are constructed on the basic principles of synergetics in which the analogy between pattern recognition and pattern formation is exploited. We show that the information flow in such computers can be determined explicitly. In this way the channel capacity, needed in such parallel computers, can be determined.

ISSN:0003-3804    

DOI:10.1002/andp.19915030109

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractFor electron energies from direct ionisation threshold up to several eV above cross sections for the production of He+, He2+, Ne+up to Ne4+, Kr2+, Kr3+and Xe2+up to Xe4+ions by single electron impact on atoms were measured. By a least square fit a power law was fitted to the cross sections. The exponents obtained by this procedure are compared with several models, i.e. a simple phase‐space calculation, the Wannier model considering interelectronic repulsion and a statistical approach similar to Russek's statistical energy deposition model. We find that especially ionisation of many‐electron atoms to high degrees of ionisation can not be described by the Wannier model, however, within the statistical appro

ISSN:0003-3804    

DOI:10.1002/andp.19915030110

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractWe extend Blatt's and Lim's calculations for the energy of the helium trimer (4He)3, for a Herzfeld potential. We use the unitary pole approximation. We constrain the effective range and scattering lenght to values of 7.4 A and infinity, respectively. As the core radius increases from 0 to 2.8 A, the trimer energy increases monotonically from −97 to −59 millikelvin. The Yamaguchi potential gives a trimer energy of −123 mK. Two additional two‐body parameters suffice to fit these, and earlier, calculations of the trimer energy: i.e., the expectation value of the kinetic energy for the dimer, and Sprung's wound int

ISSN:0003-3804    

DOI:10.1002/andp.19915030111

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY