Nuclear charge distribution of41Ca

Abstract

The mean square nuclear charge radius of 41Ca equals the one of double magic 4~ within 0.006 fin.The nuclear charge and mass distribution of Ca nuclei 40 between the two double magic isotopes 20Ca20 and 48 2oCa2s has been the testing ground for practically all of the experimental methods to determine these quantities. Double magic 4~ has equal numbers of protons and neutrons and is considered extremely spherical.Addition of one neutron in the .1"7/2 shell yields information about the penetration or polarization of the 4~ core by a single nucleon. Incorporation of further neutrons or neutron pairs into the ./7/2 shell up to the closed configuration of double magic 4SCa opens the way for a study of changes in the radius of the Ca proton core if the neutron number is changed by as much as 40 %. In the sense outlined above, the long chain of stable nuclei of Ca can be regarded as a unique target for the study of the distribution of nuclear matter, in particular for light nuclei. The facts of (a) and (b) imply that, as the J7/2 shell is filled, these excess neutrons form a skin outside the 4~ core. The anomalous behaviour of (c) can be interpreted as a partial break up of the first fT/z neutron pair by the additional neutron which form altogether a layer of neutrons around the 4~ nucleus. In order to shed some more light on the peculiar trend of the Ca nuclear charge distributions it is indispensable to study the influence of a single neutron on the 4~ core. This paper reports such study, the determination of the nuclear charge radius of radio-41 active z0Cazl which was unknown so far. The charge distribution of 41Ca was measured via its optical isotope shift in a tuned dye laser spectroscopy experiment whose details have been described previously [2, ll, 12]. Advantages of the experimental technique applied here compared to other methods are that extremely small quantities of the isotope under investigation can be studied even in the presence of large quantities of other isotopes, and that additional information on the nuclear charge distribution can be obtained from the quadrupole moment Q, because the atomic hyperfine structure can be measured. The radioactive isotope 41Ca, which decays by electron capture to 41K with a half life of ~ = 1.3 -l0 s y, has been produced by neutron capture of 4~ Since the cross section for this process (a=0.40b) is rather small, a 41Ca-concentration of only one part in thousand could be obtained after a year of irradiation, even though a high flux of 3 9 1014 thermal neutrons cm-2 s-1 at the reactor facility in Mol/Belgium was used. The experimental technique applied here was sensitive to small amounts of 4~Ca (>10 4) in the presence of nearly 100 % 4~ and possible tiny impurities of other

Nuclear electric quadrupole moment of41Ca by laser-RF spectroscopy

“…Ca was produced by neutron capture from high purity 4~ in the chemical form of carbonate [7]. Since the cross section for this process is very small (o-=0.4b) a 41Ca concentration of only several 10 -3 could be obtained even though the sample was Jr-radiated with neutrons in a high flux reactor for one year.…”