Nuclear Electric Monopole Transitions inO16,Ca40,

Abstract

A study was made of electric monopole transitions from the 0+ first excited states of certain nuclei. A search for 6.05-Mev O' EO conversion electrons gave an upper limit of 1&(10 4 for the ratio of the probability for conversion electrons to that of pair emission.Ca 0 EO conversion electrons were observed and a ratio of W"""""/W~, ;, = (6.94&0.20)X 10 ' was obtained. The momentum distributions of both components of pairs from the first excited state were observed. An upper limit of 6X10 ' was placed on the ratio of double gamma emission to pair emission. The energy of the first excited state was found to be 3.353~0.003Mev by measurement of the conversion electron energy. An excitation function for population of the first excited state of Ge'~b y inelastic scattering of protons was observed between 2.3 and 6.2-Mev proton bombarding energy. The E and (X+M +I&7+0) EO conversion electrons were resolved and the ratio Wrr/W&z+sr+&v+o& 8 70+0 06 was. obtained. The energy of the erst excited state was found to be 0.690+0.001 Mev.An excitation function for population of the first excited state of Zrgo by inelastic scattering of protons was obtained between 3.35 and 6.5 Mev proton bombarding energy. The momentum distributions of both components of pairs were observed. The energy of the first excited state was measured as 1.762~0.002Mev. 2.38&0.08 was obtained for the ratio W", """"/W~", . The X and (L+M+I&'/+0) conversion electrons were resolved and the ratio Wz/W&IyM~Nyo& 7 06+0.08 was obtained.All results are consistent within experimental errors with theoretical predictions.A study was made of the relative decay rates of the electronic decay modes in the cases of 0' y Ca ) Ge ', and Zr". Nuclei with 0+ first excited states were chosen because of the absence of competing gamma cascades and because of the relatively high (p, rs) thresholds in these magic nuclei. In addition, a search for double gamma emission was made in the case of Ca".

Electric monopole transitions from low energy excitations in nuclei

“…Decay by IP formation only becomes possible above 1.022 MeV. For example, the 1.761 MeV 0 + excited state in 90 Zr (which is the first excited state in this nucleus) decays 12,13 with probability P IC :P IP :P 2φ = 0.70 : 0.30 : 10 −4 . The IC process for E0 occurs primarily through the 1s(K) and 2s(L 1 ) shells.…”

First measurement ofK-shell-electron to internal-pair conversion probability ratios forE0 transitions inf p shell region

“…Experimental K-shell-electron to internal-pair conversion probability ratios can be compared with the calculated ratios of Qr/O., since the monopole strength pZ(E0) is independent of the E0 decay mode. Experimental values for K-shell-electron to internal-pair conversion probability ratios have been obtained, for example, for E0 transitions in 160 [2], 4~ [3], 42Ca [4J and 9~ [3J. The lack of experimental data in the fp shell nuclei is due to difficulties in detecting weak E0 internal-pair transitions of 2-3 MeV energy.…”

“…are also included in Table 1 [3] c From [4] basis of [1] and [17]. Numerical results, in tabular form, are given in [15].…”

Isobaric analogue resonances in71As through proton elastic scattering on70Ge

“…It is of interest to note that such structures of about 20 keV width have also been observed below the threshold of IAR in 72Ge(p, p) (Betigeri et al 1969), 72Ge(p, p'e) (Betigeri et al 1972a), 72Ge(p, 7) (Baba et al 1976) and 9°Zr(p, p'e) (Nessin et al 1962). It has been pointed out by Baba et al (1976) that such widths and spacings typically occur at about 6 MeV excitation.…”