Die lage der ersten anregungsstufe in kernen mit gerader protonen und gerader neutronenzahl

Abstract

The introduction refers to previous short communications [3] on the first excited state of even-even nuclei (Chap. 1). A survey shows that the lowest excitation energy of even-even nuclei is a smooth function of the neutron and proton number. In sequences of neighbouring nuclei the excitation energy increases if the number of protons or of neutrons approaches the next magic number (Chap.2). Several nuclei which seemed to disobey this rule were reinvestigated experimentally, and in every case the new data obtained confirm the rule (Chap.3). The 145 keV radiation which accompanies the transmutation of Cl34 into S34 [29] is an isomeric (M 3) transition between the known33-min state and the ground state of Cl34, the half life of which is 1.45 s. An 0+ → 0+ transition with an ft-value of 2 700 s leads directly to the ground state of S34 (§ 3.2). Two different isotopes of antimony, Sb12 and Sb116, have indistinguishable half lives of (16 ±2) min. The 1.3 MeV level which previously was attributed to Sn120 [42] belongs to Sn116. The 60-min activity, with a γ-ray of 0.70 MeV [41], probably has to be reassigned to mass number115 (instead of 116) (§ 3.10). In Hg196 a reported γ-ray of 175 keV [46] could not be confirmed, and a new line corresponding to a first level at 426 keV was found, which agrees with our rules (§ 3.13). Further experiments deal with Mo96, Zr92 and Mo92. The dependence of the lowest excitation energy on the number of protons and neutrons is interpreted in terms of the shell modell (Chap.4). It is shown that a strong configurational interaction must be assumed (Chap.5), and that in general the first excited state is due to a simultaneous excitation of the neutron and the proton structure (Chap.6).