Levels ofSi29with Excitation Energy Below 6.4 MeV

Abstract

Levels in Si~were populated with the reaction Mg (e, n)Si 9 and subsequent y radiation from the various levels was detected with a 37-cm Ge(Li) y-ray spectrometer. Beginning with the 4.08-MeV level, y-ray angular distributions (0'~0 & & 90') were measured at incident bombarding energies near threshold (Q0 =0.033 MeV) for levels with excitation energies between 4.08 and 6.38 MeV. The target was a Mg metal foil, on the order of 0.5 mg/cm thickness.Branching ratios and excitation energies of the various levels were deduced from y-ray pulseheight distributions. y-ray angular correlations obtained at G. bombarding energies near threshold were treated as originating from residual nuclei having magnetic quantum numbers m~= 2 and 2. Analysis of these angular correlations in terms of level spin and y-ray multipole mixing was then undertaken. Mean lifetimes (or limits) for these levels were determined using a variant of the Doppler-shift-attenuation method, which involves measurements of the attenuation for two targets of different stopping power. Both Mg foils and Mg 6-Au alloy foils (10 at.% Mg and 90 at.% Au) were used. From these measurements, excitation energies (in keV), level spins, and lifetimes (in fsec) for these levels were deduced; these are, respectively, 4079These data may be combined with the results of other investigations to arrive at a fairly complete level scheme for Si29 in the energy interval 0&E"(Mev) & 6.38, including a description of the electromagnetic decay properties. These properties are compared with model predictions of the properties of Si29.

Spectroscopy and shell model calculations in Si isotopes

“…This transition has been addressed in the previous studies, especially by Bardin et al [27,28] to explore the development of collectivity in the nucleus. The negative parity sequence was identified as a possible candidate for a rotational structure.…”

“…This is indicative of a change in the structure therein. Indeed, the 3624 keV (7/2 − ) level has been interpreted as the band-head of the K π = 7/2 − band in the previous studies [10,28]. Such a scenario warrants a re-examination of the 1596 keV transition with the contemporary spectroscopy tools, as used in the present investigation.…”

“…Large basis shell model calculations have been carried out for the 29 Si nucleus and the neighbouring 28,30 Si isotopes using the shell model code NuShellX@MSU [29]. The U SDA [8] a The presence of a dominant side-feeding allowed for assignment of only an upper limit on the lifetime.…”

“…The results have been compared with shell model calculations using updated interactions and larger model spaces and are found to be in close agreement. The large basis shell model calculations, have been extended to the neighbouring 28,30 Si nuclei [7,20] for a comparative interpretation. The calculations for 28 Si could satisfactory reproduce the deformed states reported previously by Jenkins et al [20].…”

“…The large basis shell model calculations, have been extended to the neighbouring 28,30 Si nuclei [7,20] for a comparative interpretation. The calculations for 28 Si could satisfactory reproduce the deformed states reported previously by Jenkins et al [20]. Further, the predicted negative parity states in 30 Si, are in reasonable agreement with the observed level sequences.…”