C.J. Gorter

Asymmetry of the positon emission by polarized 58Co-nuclei

L e e a n d Y a n g 1) h a v e recently suggested t h a t t h e law of p a r i t y should be given up for weak i n t e r a c t i o n s a n d t h a t c o n s e q u e n t l y t h e i n t e n s i t y of b e t a-r a y emission m i g h t differ in t h e directions parallel a n d antiparallel to t h e nuclear spin. W e h a v e confirmed this prediction for t h e positon emission of 58Co. 8 microcuries of r a d i o a c t i v e cobalt were c o n t a i n e d in a 0.15 m m layer of Ce2Mgs(NO3)I~.24H20 grown on a large n o n-r a d i o a c t i v e crystal, which could be cooled down b y a d i a b a t i c d e m a g n e t i z a t i o n ~). T h e nuclear spins could be polarized in t h e vertical direction b y m e a n s of a coil m a g n e t p r o d u c i n g a field of 300 Oe, according to t h e hyperfine s t r u c t u r e polarization m e t h o d 3). T h e e m i t t e d positons were detected w i t h o u t i n t r o d u c i n g a particle c o u n t e r into t h e c r y o s t a t by m e a n s of a device suggested to one of us (C.J.G.) in a discussion after a colloquium which he gave in Berkeley (Cal.) in 1952. T h e crystal was m o u n t e d w i t h t h e r a d i o a c t i v e layer d o w n w a r d a n …

Asymmetry of the positon emission from polarized 58Co and 52Mn nuclei

Synopsis A method for measuring the asymmetry of positon emission by studying its annihilation radiation is described and discussed. If the directional distribution of the positons from 58 Co is written as W(ϑ) = 1 + f 1 β cos ϑ with f 1 = 〈 I z 〉/ I , the experimental result can be given as β = (0.24 ± 0.05 ( v/c ). Four different interpretations of this result are discussed. The asymmetry fo 52 Mn is zero within the experimental error. It follows that the nuclear spin of 52 Mn is 6

A FEW PROVISIONAL CONCLUSIONS FROM OBSERVATIONS ON ALIGNMENT OF COBALT NUCLEI

From the observed anisotropy of the gamma-ray emission of aligned 60CO the magnetic moment of this nucleus is estimated to be 3.2 nuclear magnetons. From the dependence of the anisotropy on a magnetic field it is concluded that the hyperfine splitting of 59Co in the salt concerned is 0.13 cm−1 between consecutive levels.

Alignment of 56Co nuclei: Part I. Experimental results; determination of magnetic moment

Synopsis A dilute copper ammonium Tutton salt, containing a small amount of 56 Co, was cooled by adiabatic demagnetization to about 0.02°K and an anisotropy in the angular distribution of the gamma intensity, resulting from the nuclear alignment, was found in each of the six gamma rays. An estimate of the magnetic moment of 56 Co yielded 2.8 ± nuclear magnetons.

Experiments on oriented 60Co nuclei

Synopsis In this paper a survey is given of the investigations on oriented 60 Co nuclei contained in (Co, Cu, Zn) (NH 4 ) 2 (SO 4 ) 2 .6H 2 O crystals. Crystals of three different compositions were used with 0%, 10% and 20% copper, respectively. By adiabatic demagnetization the crystals were cooled down to about 0.02°K. During the warm-up the angular distribution of the gamma rays emitted by the 60 Ni nuclei was measured for different directions of the counters. The essential parts of the experimental set-up are described. The measured anisotropic angular distributions are given as functions of the magnetic temperature T *. The results are compared with theory. They are in good agreement with the 4-2-0 spin assignment to the 60 Ni levels concerned. An estimate of the magnetic moment of the 60 Co nucleus yields a value of 4.3 ± 0.2 nuclear magnetons, if one assumes the spin of the 60 Co nucleus to be 5.

Paramagnetic absorption and dispersion in chromium potassium alum

Zusammenfassung Es werden die Resultate mitgeteilt einer Untersuchung uber die paramagnetische Absorption und die paramagnetische Dispersion von Kalium-Chromalaun. Wahrend die Resultate fur die Dispersion in guter Ubereinstimmung stehen mit den Casimir-Dupreschen Formeln ist dies nicht der Fall fur die Absorption in niedrigen Magnetfeldern und hohen Frequenzen. Die Diskussion dieser Diskrepanz fuhrt nicht zu einer endgultigen Schlussfolgerung.

Measurements of the anisotropy of gamma radiation emitted by orientated 52Mn nuclei

Synopsis Measurements are reported of the anisotropy of the intensity of the gamma radiation emitted by 52Mn nuclei, orientated at low temperatures. The nuclei were orientated in Ce-Mg-nitrate single crystals both by the alignment method and by polarization in an external magnetic field. From the results it is concluded that the spins of the 3 excited states of 52Cr are 2, 4 and 6, all radiations being E2 (fig. 1). The alignment anisotropy as a function of temperature (fig. 3) showed an unusual character, which has been compared with the results obtained by the Oxford group on 54Mn 1) (fig. 4).

Anisotropic angular distribution of gamma radiation emitted by a source containing aligned 60Co nuclei

Synopsis The anisotropic angular distribution of the gamma-radiation from aligned 60Co-nuclei has been measured as a function of the magnetic temperature T* of a source, consisting of six (Co 1%, Cu 10%, Zn 89%) (NH4)2(SO4)2.6H2O single crystals. The angular distribution has been determined from T* = 0.02° to T* = 0.08°. The maximum anisotropy at T* = 0.02° is 30%. The experimental results are in reasonable agreement with the theory if we assume the angle 2a between the two axes of nuclear alignment to have the value of 72°. The scintillation counter device and the counting technique are briefly described. The anisotropy effect does not strongly depend on the amount of copper, used as a cooling agent in the crystals. With 20% copper a somewhat larger anisotropy could be achieved.

Paramagnetic dispersion in vanadous ammonium sulphate

Zusammenfassung Es wird die paramagnetische Dispersion von Vanadium-Ammonium-Sulfat aufgefunden und studiert. In Ubereinstimmung mit der theoretischen Erwartung ergibt sich eine Analogie zwischen dem Salz mit zweiwertigen Vanadium-Ionen und den Salzen, welche dreiwertige Chrom-Ionen enthalten.