Das Internationale Einheitensystem Entwicklung der Einheiten und heutiger Stand

Metrological aspects leading to the International System of Units (SI) are given - using typical examples, especially in the case of the units meter, ampere, mol, volt, and ohm. The founding of units on fundamental constants, the continuity of units in the case of their redefinition, and the question of coherence are discussed in detail. The definitions for all SI base units as well as the international recommendations for the realizations of the units volt and ohm are expressed via equations of quantities. The interdependencies of the most important SI units are given in a flowchart. (orig.)SIGLEAvailable from TIB Hannover: RN 2495(58) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

A laser light source for circularly polarized VUV radiation

Irrgang R, Drescher M, Gierschner F, Spieweck M, Heinzmann U. A laser light source for circularly polarized VUV radiation. MEASUREMENT SCIENCE & TECHNOLOGY. 1998;9(3):422-427.A laser-based light source for circularly polarized VUV radiation generated by nonlinear sum-frequency mixing is described. By choosing an appropriate nonlinear resonant process a light flux of up to 6 x 10(10) photons s(-1) at a bandwidth smaller than 1.2 cm(-1) is achieved. The determination of the polarization state is performed by means of using a four-mirror analyser. A degree of circular polarization greater than 0.99 was found for several mixing processes. These properties make this instrument an ideal source for high-resolution spectroscopic studies of polarization-dependent photo-ionization or photoemission at photon energies up to 14 eV

PFI-ZEKE spectroscopy of the (2)Pi spin-orbit components of HBr+

Irrgang R, Drescher M, Gierschner F, Spieweck M, Heinzmann U. PFI-ZEKE spectroscopy of the (2)Pi spin-orbit components of HBr+. In: Journal of Electron Spectroscopy and Related Phenomena. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. Vol 80. ELSEVIER SCIENCE BV; 1996: 5-8.The PFI-ZEKE method was applied for examination of the rotational structure of the (2) Pi spin-orbit components of HBr+ (v(+)=0). Precise absolute values for the position of rotational thresholds were obtained. Additional lines not compatible with ionization thresholds are attributed to slow electrons from autoionizing states attached to neutral molecules and field-ionized by the extraction pulse

High-resolution experimental determination of the angular distribution and spin polarization of xenon 7d ' and 9s ' photoelectrons and comparison with theoretical results

Spieweck M, Drescher M, Gierschner F, Irrgang R, Heinzmann U. High-resolution experimental determination of the angular distribution and spin polarization of xenon 7d ' and 9s ' photoelectrons and comparison with theoretical results. PHYSICAL REVIEW A. 1998;58(2):1589-1591.Using narrowband tunable linearly br circularly polarized VUV radiation an examination of the dynamical parameters describing the autoionization process of atomic xenon was performed. With a resolving power of similar to 10(5) in the excitation step a fully resolved determination of the position, magnitude and shape of the angular distribution and integral spin-polarization resonances was possible for the low Rydberg orders n=7 and n=9 of the d and s series, respectively. Comparisons are drawn between the experimental data and some theoretical calculations published in recent years. [S1050-2947(98)00108-5]