Radiationless transition probabilities in muonic208Pb,232Th, and238U

Folger

et al. 1992

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A study of muonic 238U has been performed in a combined (p-, 7f) and (#-, 7t') coincidence experiment to investigate the role of non-radiative transitions and their fission probabilities. An augmentation of the outer fission barrier of AEb = (0.6___ 0.1) MeV due to the presence of the muon is deduced. A significant contribution to the prompt fission yield not only results from the (2p~ Is) and (3d-+ l s) non-radiative transitions, but also from other radiationless transitions. Specifically, the measured fission probabilities of the transitions (2p-~ls), (3 d ---, l s), and (3p--*ls) are (1.5• (5.7 • 1.7)%, and (5.3 • 1.9)%, respectively.

“…and of Pnr(3 d-~ ls)=(12.8+ 1.4)~ have been obtained from the 7),-coincidence data [8]. From (6) and (7) Table 2.…”

Section: Evaluation Of the Fission Probability Of The Nr (3d--* Ls)mentioning

confidence: 99%

Section: Evaluation Of the Fission Probability Of The Nr (3d--* Ls)mentioning

confidence: 99%

“…transitions has been investigated both theoretically [-2-4] and experimentally [5][6][7][8]. transitions has been investigated both theoretically [-2-4] and experimentally [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…transitions is discussed extensively in [8]. 2) has been a combined (/1-, },f) and (~-, 7]') measurement to investigate the n.r.…”

Section: Introductionmentioning

confidence: 99%

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Nuclear excitation and prompt fission in muonic238U

Folger

et al. 1992

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“…The pion contamination of the beam was less than 10 -4. The set-up, similar to previous experiments [27][28][29], is sketched in Fig. 2.…”

Section: Experimental Set-upmentioning

confidence: 99%

Delayed muon induced fission of209Bi and the role of meson-exchange currents

Paganetti

et al. 1992

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Radiationless transition probabilities in muonic209Bi

Paganetti

et al. 1992

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Abstract:The probability for non-radiative (n.r.) excitations in muonic 2~ was determined from a (#-,72C)-measurement by comparing the intensities of muonic X-ray transitions in single and coincidence spectra. The values of P,. ~.(3p--~ls) =(17.9• and P,.~.(3d-~ls) were studied in continuation of the preceding experiments on zCSpb, 232Th, and 23su [9].The experiment was performed using the/zE4 channel of the Paul-Scherrer-Institut (PSI). The experimental setup is described in more detail in ref. 10, which contains the result of the simultaneously measured fission probability of muonic 2~The beam intensity, measured with a scintillator telescope, was 2• muons per second. Two large volume Ge-detectors each with a BGO-Compton suppression system were used to detect the muonic X-rays. A large CsF-crystal (5"x5") was employed in addition to define coincidences between muonic X-rays.Following the conventional nomenclature, the probabilities for a certain transition refer to the population of the initial level. The formalism to determine the fraction of n.r. transition strengths between the levels of the muonic cascade has been outlined by RSsel et al. [9]. The probability for a non-radiative (2p--~ls)-transition P~.~.(2p--ls) has been determined from the analysis of the X-ray spectra recorded by the CsF-crystal. In order to evaluate the probability P,.~.(3p-~ls) it is necessary to analyze muonic transitions which populate the 3p-level. tn muonic 2~ the (4d~3p)-transitions clearly identified in the Ge-detectors have been used for this purpose. * Present address:By considering all radiative and n.r. decays of the 3d-level Pn.T.(3d~ls) has been obtained. The total transition probability P(3d~2p) has been evaluated by comparing the muonic X-ray spectra measured as single events with those measured in coincidence with the (2p-*ls)-transition. For muonic 2~ the results for P(3d--*2p) show significant deviations for the different fine structure transitions. This effect has previously been observed for 2~[9]. For 2~ it was possible to analyze the n.r. decay width F .... (3d-~2p). For this purpose the formalism described in ref. 9 has been extended accordingly: P,~.r.(3d--+ls) = 1 -P(3d~2p) -P,.,~a(3d---~ls) = 1 -P(3d--~2p) -P(3d~2p)r,aa(3d~ls) X rTo.(3d-2p) + r ... . (3d-,2p)The ratio of the radiative decay widths Fr~d(3d---~ls) / Fr, has been calculated by Lohs et al. [11]. Taking into account the non-radiative E3-transitions (3ds/2~2p3/~) and (3d~/z-~2pl/2) due to the E3-resonance in 2~ [12,13] the non-radiative decay width F .... (3d---~2p) has been estimated. This has been done here by the determination of the intensities of the nuclear 2c-rays belonging to the decay of the resonance. We have neglected other n.r, (3d---+2p)-transition modes and a possible population of these isomer shifted nuclear levels, following energetically higher nuclear excitations by other n.r. transitions. Therefore this gives only an approximation for the probability of a n,r. (3d-+2p)-transition.In table 1 the results for the n.r. transition pr...