Observation of nuclear rotational spectra in pion capture on 165Ho and 175Lu

High spin states and neutron multiplicities after pion capture in181Ta and209Bi

“…The SIN group studied prompt gamma-ray spectra following pion capture in 165Ho and 17SLu isotopes [5]. In these experiments it was shown that the maximum cross-section occurred at x=4 and 5, respectively, and that the rotational spectra were excited up to 12 + for different Dy and Yb isotopes.…”

“…In addition the relative probability of pion capture on np pairs relative to that on pp pairs or heavier clusters can be studied by measuring the total yield of isotopes with an atomic number one unit lower than that of the target nucleus. Recently, experimental groups at Dubna I-2] and SIN [5] reported that nuclear states with high spins were populated in pion capture. The Dubna experiment, using activation techniques, showed, for example, that a high-spin isomer with I=37/2 in 177Hf was produced in the lSlTa(Tr-,4n) reaction.…”

“…If the absorption takes place in the * Present address: Natuurkundig Laboratorium der Vrije Universiteit, Amsterdam ** On leave from the Institute of Nuclear Physics Research, Amsterdam nuclear surface region, one of the nucleons is likely to escape the nucleus, which may result in a large nuclear angular momentum change. The other nucleon, when captured by the nucleus, causes a considerable nuclear excitation followed by the evaporation of nucleons, predominantly neutrons [5] with a maximum number of about [8][9]. If the absorption takes place in the interior of the nucleus the emission of a larger number of evaporation neutrons is possible (maximum number --~17, see [6,14] however, the angular momentum should be smaller.…”

Nuclear reactions induced by stopped negative pions in133Cs,93Nb and45Sc

“…The population of high-spin states of rotational bands in heavy nuclei was observed in SIN [8,14] and in CERN [13]. In our experiments several isomeric methastable states were identified from which the isomeric yield ratio for the isomeric pairs sTm, gy and 86~,gy induced in (n-,p5n) and (re ,p6n) reaction respectively were determined.…”

“…The absorption of negative pions has been studied in the past by emulsion, neutron dosimetry and activation technique reviewed for instance by Koltun [-5] and by Htifner [3]. In the last years using more precise experimental technique the formation and the de-excitation of the residual nuclei [6][7][8][9][10][11][12][13][14], neutron and charged particle spectra [16,17] were observed. However, there is insufficient systematic information about neutron multiplicity, charged particle emission and angular momentum transfer.…”