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Since absolute energy measurements are not possible with doubly focussing magnetic spectrometers, most α-spectroscopists relied largely on a few standard energies determined by Rosenblum and Dupouy and by Briggs. Although more absolute results became available later, some major inconsistencies remained and caused difficulties in interpreting α-ray spectra. Since 1969, 22 α-emitters and 35 lines have been measured in the absolute magnetic spectrograph of the BIPM. The results are compared with the values found in the most commonly used compilations. They are useful in calibrating various types of spectrometers and in atomic mass calculations. A new compilation of α-energy data is now in preparation.

Among 18 000 photographs taken during an experiment with a large cloud chamber at the Jungfraujoch (3 580 m) 13 examples of the decay of charged V-particles have been observed. A summary of the measurements of the 13 particles is given. Two of them are produced in nuclear interactions of remarkably low energy. The average time that the particles would have taken to cross the chamber, if they had not decayed in flight, is ∼10-9 sec, and the distribution of the decay events does not differ significantly from that which would be expected for particles with a mean life greater than 10-9 sec.

The validity of the Hartree correction formula for a semicircular spectrometer is discussed and some corrective terms proposed for the influence of anomalies in field direction and uniformity. A method of measuring the deviations from the ideal direction of field is demonstrated and the magnitude of the corrections for a particular case evaluated. demonstrated and the magnitude of the corrections for a particular case evaluated.

Conclusions(1) For lack of a better name, the antibodies causing flocculation of antigen in human syphilitic serum might be termed “flocculins”. (2) It has been shown that flocculate obtained from human syphilitic serum, by means of flocculation tests for syphilis, will cause positive flocculation tests in rabbits when inoculated intravenously. Such reactions will remain positive for at least 2 months after the last injection. Rabbits inoculated with antigen emulsion alone do not develop positive flocculation tests. (3) Apparently, the serological factors involved in the formation of “flocculins” in the animal body are influenced by ether anesthesia. (4) Flocculate obtained from the serum of a rabbit injected with flocculate from human syphilitic serum, will cause the formation of “flocculins” in another rabbit when injected intravenously. (5) The serum of a rabbit inoculated with a definite number of flocculate units, may develop many more units than were thus injected.

New absolute energy measurements of α-particles from 20 natural and artificial emitters are reported, some of which are first absolute values. The uniform field 180° magnetic spectrograph is described in detail. Accurate length and field measurements and line shape extrapolations have been given special attention. A detailed error analysis is presented.

Several excited states of 28Si can be reached either by capture of protons by 27Al or by capture of α particles by 24Mg through resonant reactions whose total width is quite narrow. Thus it is possible to obtain very accurate values of the mass difference of 27Al24Mg or the Q value of the reaction 27 Al(p, α)Mg 24 by simply measuring the two resonance energies of the primary proton and α particle, respectively. It is found that there is a significant difference of about 7 keV between the values determined in this way and the Q value and mass differences listed in the tables of Everling et al. For the Q value this difference is more then 5 times the combined errors.

A revised compilation of experimental values of α-particle energies and intensities is presented. It includes all α-emitters for which the stated uncertainty of energy measurements is not larger than 5 keV. All α-lines with at least 5% of the total α-intensity are registered. The energy values have been adjusted with recent absolute determinations of standard energies. The weighted means form a consistent set of recommended energy values.

Eight hundred tracks of slow particles have been photographed during a cloud chamber experiment on penetrating showers. Measurements of tracks produced by ten heavy, negative, non-decaying particles are presented. The total observed time of flight of these particles is l·6 × l0-8 sec. After combining this time with the number of slow V-particles observed to decay in the cloud chamber, it is concluded that at least one type of heavy meson must have a mean life greater than 4 × 10-9 sec.

Nearly 400 reaction energies have been recalculated, using the most recent calibration data, in order to get a reliable basis for nucleidic mass adjustments.

Enthält: Abdankungsansprache von Otto Rytz, Pfarrer an der Kirche Enge in Zürich

Enthält: Abdankungsansprache von Pfarrer Otto Rytz