R.J. Peterson

The energy-loss spectrograph at the university of colorado cyclotron☆

Abstract A spectrograph system has been developed to satisfy both the requirements of high resolution charged particle spectroscopy and those of neutron time-of-flight spectroscopy. In the charged particle mode the instrument is an energy-loss spectrograph with a fractional energy resolution of 3 × 10−4, while in the neutron time-of-flight mode a resolution of 40 keV is achieved with low background at a neutron energy of 16 MeV. The novel feature of the spectrograph is that the charged particle and neutron analyzing systems are both fixed in position with the reaction angle varied by rotation of the beam preparation system.

The direct (p, α) pickup reaction on the even Zr isotopes

Abstract The (p, α) reaction has been studied on the four even isotopes of zirconium at a proton energy of 22.8 MeV. At this energy, the reaction mechanism was demonstrated to be a direct pickup, leading primarily to hole states in the residual yttrium. A cluster-transfer DWBA calculation was found to account for the observed shapes of the angular distribution, and in particular, reproduced the striking j -dependence between 1 2 − and 3 2 − states. On the basis of the similarity to observed angular distribution to states of known spin, a number of new angular momentum assignments are made. Candidates for states of high spin, up to 15 2 − , are also found. Attempts have been made to fit the observations into a weak coupling scheme based on the known single-nucleon holes coupled to states of the zirconium isotopes.

A study of the 106Pd(p, d)105Pd and 106Pd(3He, d)107Ag reactions

Abstract The 106 Pd(p, d) 105 Pd reaction has been studied at 22.9 MeV with an energy resolution of 13 keV. Angular distributions permitted the assignment of l -values and the extraction of spectroscopic factors for 13 states including several previously unresolved l = 2 transitions. The 106 Pd( 3 He, d) 107 Ag reaction has also been studied at 32.8 MeV with a resolution of 20 keV. Angular distributions were obtained, l -values assigned and spectroscopic factors extracted for 14 levels including many not observed previously in a proton transfer reaction. The level structure of 105 Pd and 107 Ag is discussed particularly in terms of quasirotational bands.

Proton stripping reactions on 194Pt, 196Pt AND 198Pt

Abstract The ( 3 He, d) and ( 4 He, t) single proton stripping reactions have been studied on 194, 196, 198 Pt at beam energies of 41.2 and 35.1 MeV, respectively. It is observed that the distribution of l = 0 and l = 2 stripping strength does not depend strongly upon the target species, while the excitation energies of prominent 9 2 − , 11 2 − and 13 2 + states increase dramatically with increasing neutron in the target. These results are interpreted as evidence for a negative deformation of the high spin orbitals, decreasing in magnitude for the heavier isotopes. The role of the rotation-alignment coupling is noted in the large spectroscopic factors for the prominent high spin bandheads.

Two-nucleon pick-up from spin-12 targets (II). 89Y

Abstract The angular distributions for the 89Y(p, t), (p, τ), and (d, α) reactions are compared to DWBA predictions and to the data for the 90Zr(p, t) and (d, α) reactions. Several new spins are assigned to levels of 87Y. A weak coupling model is tested by the comparison between the reactions on 89Y and 90Zr, and found to fail. The (d, α) reaction is found to populate strongly levels at excitation energies of 2.70 MeV and 3.07 MeV in 87Sr, corresponding roughly in Q-value and strength to states formed in ths 88Sr(d, α)86Rb reaction.

The (3He, d) reaction on 24Mg and 28Si at 38.5 MeV

The (3He, d) reaction at a sufficiently high energy is considered to be a reliable single-proton stripping direct reaction. The data for the low-lying states produced by this reaction on 24Mg and 28Si are compared to the predictions of the strong-coupling rotational model. The agreement with the model predictions for 25Al is quite good, both for the single-proton spectroscopic factors in that nucleus and most particularly for the excitation of 72+ states in 25Al and 29P by two-step processes.

Proton stripping to 14N

Abstract The 13 C( 3 He, d) reaction at a beam energy of 43.6 MeV was used to examine levels of 14 N up to 11.7 MeV over an angular region including the main stripping peaks. Many spectroscopic factors were determined reliably for known states and found to be mostly in good agreement with calculations for the stronger levels. Several new spin or parity assignments are made at high excitation.

Level structure of 106Ag

Abstract The level structure of 106 Ag has been investigated through the use of the 103 Rh(α, nγ), 105 Pd( 3 He, d), 107 Ag(p, d) and 104 Pd( 3 He, p) reactions. The charged particle reactions provided the energies of 47 levels ranging up to 1684 keV and l -values were determined from the angular distributions for the neutron and proton transfer reactions to most of the states. Fifty-two γ-rays were assigned as transitions between the levels resulting from the charged particle data. Through the use of a combination of the l -values and γ-ray transitions the members of the 1g 9 2 -2d 5 2 and 2p 1 2 -2d 5 2 configuration multiplets have been deduced. The 6 8.4 d isomeric state has been located at 88 keV. The measurement of Q -values for the charged particle reactions has permitted determination of the mass of 106 Ag with greater precision than previously.

Two-nucleon pick-up from spin-12 targets (I). 57Fe

Abstract We have measured differential cross sections for the (p, t) and (p, τ) reactions on 57Fe at a proton energy of 27 MeV, and for the (d, α) reaction at 16.0 MeV. Several spin-parity assignments for 55Fe and 55Mn are suggested, and comparisons to DWBA calculations allow the identification of those states with a strong two-hole parentage. Attempts to find simple relations between these results and the yields from two-nucleon pick-up reactions on nearby doubly even targets were not successful.

Semi-microscopic analysis of multi-nucleon transfer and the 40Ca(α, p)43Sc reaction☆

Abstract A semi-microscopic model for analyzing multi-nucleon transfer reactions in the distorted-wave Born approximation is presented. This model, which is shown to be compatible with other semi-microscopic models, employs cluster form factors. The cluster spectroscopic factors are calculated using shell-model wave functions. Data from the 40Ca(α, p)43Sc reaction are presented and used to test the model. The relative cluster spectroscopic factors for a number of levels are found to be in agreement with those calculated using wave functions in an ( f 7 2 ) 3 basis.