Systematics of the (t, p) reaction in Yb and Hf isotopes near the N = 108 "subshell closure"

1983 ◽  
Vol 61 (3) ◽  
pp. 460-472 ◽  
Author(s):  
D. G. Burke ◽  
I. Nowikow ◽  
Y. K. Peng ◽  
J. C. Yanch
Keyword(s):  
Residual Nucleus ◽  
Neutron Number ◽  
Quantitative Agreement ◽  
Angular Distributions ◽  
Published Data ◽  
Reaction Products ◽  
Structure Information ◽  
Boson Model ◽  
Subshell Closure ◽  
Photographic Emulsions

Angular distributions of protons from the 170, 174, 176Yb(t, p)172, 176, 178Yb and 178,180Hf(t, p)180, 182Hf reactions have been studied using beams of 15 MeV tritons from the McMaster University tandem Van de Graaff accelerator. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Levels up to ~2.5 MeV excitation were studied in each nuclide, with a typical overall resolution of ~15 keV (full-width half-maximum). Measurements were also made with targets of natural Yb and natural Hf, to improve the accuracy of relative strengths in each chain of isotopes, and with a target of 172Yb to facilitate the normalization of previously published data to the present results. One of the most notable features of the data is the large amount of L = 0 strength to excited Iπ = 0+ states for all cases where the residual nucleus has a neutron number N ≤ 108. The populations of these states are not explained by either the pairing rotational or vibrational models. The SU(3) limit of the interacting boson model yields qualitative but not quantitative agreement. For two of the residual nuclides studied, 178Yb and 182Hf, there was little or no nuclear structure information previously available. The (t, p) experiments have located a number of excited states in each of these cases, and also give the first measurements of two-neutron separation energies; S(n) = 12 333 ± 6 keV for 178Yb and 12 413 ± 6 keV for 182Hf.

Odd Proton States in 165Tm, 167Tm, 169Tm, and 171Tm

1974 ◽  
Vol 52 (21) ◽  
pp. 2108-2126 ◽  
Author(s):  
H. C. Cheung ◽  
D. G. Burke ◽  
G. Løvhøiden
Keyword(s):  
Proton Transfer ◽  
Nuclear Structure ◽  
Cross Sections ◽  
Quadrupole Deformation ◽  
Angular Distributions ◽  
Coriolis Coupling ◽  
Reaction Products ◽  
Structure Factors ◽  
Nilsson Model ◽  
Photographic Emulsions

Proton states in the odd mass isotopes 165Tm, 167Tm, 169Tm, and 171Tm have been studied using (3He, d) and (α, t) reactions with 24 MeV 3He and 27 MeV 4He beams. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions, giving a resolution (FWHM) of 16–18 keV. The proton transfer l values were determined from (3He, d) angular distributions and from the ratios of (3He, d) and (α, t) cross sections. Nuclear structure factors, extracted using DWBA cross sections, were compared to those predicted by the Nilsson model with pairing corrections and Coriolis coupling included. Most of the previous assignments for low lying proton states have been confirmed, and several new ones were made. It is shown that the energy systematics of the intrinsic proton states cannot be attributed to variations in the quadrupole deformation, ε2, but can be explained by a small monotonic variation in the hexadecapole deformation, ε4.

A study of levels in 155Dy using the (d,t) and (3He,α) reactions

1976 ◽  
Vol 54 (12) ◽  
pp. 1258-1273 ◽  
Author(s):  
O. Straume ◽  
D. G. Burke ◽  
T. F. Thorsteinsen
Keyword(s):  
Nuclear Structure ◽  
Cross Sections ◽  
Negative Parity ◽  
Positive Parity ◽  
Angular Distributions ◽  
Coriolis Coupling ◽  
Reaction Products ◽  
Nilsson Model ◽  
Photographic Emulsions ◽  
Peak Widths

The (d,t) and (3He, α) reactions on a target of 156Dy have been used to study the nuclear structure of 155Dy. Beams of 15 MeV deuterons and 24 MeV 3He were obtained from the McMaster University FN tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected in photographic emulsions. The (d,t) reaction was studied at 15 angles with typical peak widths (FWHM) of ~ 6 keV and (3He,α) exposures were made at 5 angles with peak widths of ~ 18 keV. The (d,t) angular distributions and ratios of the (3He,α) and (d,t) cross sections were used to determine l values for a number of transitions. It is found that the positive parity states can be described in terms of the Nilsson model when Coriolis coupling is included while for the negative parity states only the gross features are well-described this way.

States in the N = 87 Nuclei 149Sm and 151Gd Populated by the (d, t) and (3He,α) Reactions

1975 ◽  
Vol 53 (12) ◽  
pp. 1182-1192 ◽  
Author(s):  
G. Løvhøiden ◽  
D. G. Burke
Keyword(s):  
Spherical Shell ◽  
Shell Model ◽  
High Spin ◽  
Cross Sections ◽  
Striking Feature ◽  
Angular Distributions ◽  
Spin States ◽  
Reaction Products ◽  
Photographic Emulsions

The (d, t) and (3He, α) reactions on targets of 150Sm and 152Gd have been studied using a magnetic spectrograph and photographic emulsions to analyze and detect the reaction products. The (3He, α) spectra were measured at two angles for each target using 24 MeV beams of 3He. The 150Sm(d, t)149Sm reaction was studied at 13 angles with 12 MeV deuterons. The 152Gd(d, t)151Gd spectra were recorded at 4 angles with 15 MeV deuterons. The l values for a number of low spin states were determined from the (d, t) angular distributions. The ratios of (3He, α) and (d, t) cross sections were used to obtain l values for several other states. It is possible to explain the observed strength in terms of the spherical shell model although there is fragmentation of the spherical states. One striking feature is the similarity in the structures of the two nuclei. In both 149Sm and 151Gd there are high spin i13/2 states at ~0.85 MeV and h11/2 states at ~1.25 MeV.

A study of levels in 147Nd using the (d,t) reaction

1977 ◽  
Vol 55 (19) ◽  
pp. 1687-1696 ◽  
Author(s):  
O. Straume ◽  
D. G. Burke
Keyword(s):  
Ground State ◽  
State Transition ◽  
Energy Levels ◽  
Striking Similarity ◽  
Angular Distributions ◽  
Reaction Products ◽  
Proton Group ◽  
Energy Proton ◽  
Photographic Emulsions ◽  
Peak Widths

The 148Nd(d,t)147Nd reaction has been studied using 12 MeV deuterons. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected with photographic emulsions, giving peak widths (FWHM) of approximately 8 keV. The present results confirm previous indications that the highest energy proton group found in an early 146Nd(d,p) investigation does not correspond to the ground state transition, but to the level at an excitation energy of 50 keV. The (d,t) angular distributions were used to determine l-values for a number of transitions. A striking similarity is noted with the energy levels and spectroscopic strengths previously found in the isotones 149Sm and 151Gd. With the exception of the h11/2 state, it is possible to explain the observed strengths in terms of the spherical shell model, although there is fragmentation of the spherical states.

Single proton states in odd holmium isotopes

1977 ◽  
Vol 55 (19) ◽  
pp. 1657-1686 ◽  
Author(s):  
J. D. Panar ◽  
O. Straume ◽  
D. G. Burke
Keyword(s):  
Nuclear Structure ◽  
Cross Sections ◽  
Gamma Ray ◽  
Reaction Products ◽  
Excitation Energies ◽  
Light Reaction ◽  
Structure Information ◽  
Structure Factors ◽  
Nilsson Model ◽  
Photographic Emulsions

The (3He,d) and (α,t) reactions have been used to study odd proton states in 157,159,161,163Ho. The beams were provided by tandem Van de Graaff accelerators and the light reaction products were analyzed with magnetic spectrographs and detected with photographic emulsions. Spectra were studied up to excitation energies of ~1.5 MeV for each nuclide with resolutions (FWHM) of ~14 keV for the (3He,d) reaction and ~12 keV for the (α,t) reaction. Information on the l-values was obtained from the ratios of (3He,d) and (α,t) cross sections and from (3He,d) angular distributions. The results are interpreted in terms of the Nilsson model with pairing and Coriolis mixing included. Nuclear structure factors were extracted from the experimental data with the aid of DWBA calculations. Nilsson assignments from previous gamma-ray studies have been confirmed for many low-lying rotational bands. In addition, many new assignments have been made, particularly in the lighter isotopes for which very little nuclear structure information existed previously. A relatively strong l = 0 transition is found in each nuclide and arguments are made to suggest these Iπ = 1/2+ states are gamma vibrations based on the 5/2+[402] states. Similarly, strong l = 2 transitions populate states which may be Iπ = 3/2+ gamma vibrations based on the 7/2+[404] orbitals. Some interesting systematics of the behaviour of single particle states in this region are presented and some anomalies in the populations of the 1/2+[411] and 3/2+[411] states are pointed out.

Direct evidence for mixing of two-quasiproton and two-quasineutron configurations in 172Yb

1982 ◽  
Vol 60 (12) ◽  
pp. 1751-1758 ◽  
Author(s):  
D. G. Burke ◽  
J. W. Blezius
Keyword(s):  
Alpha Particle ◽  
Magnetic Moment ◽  
Direct Evidence ◽  
Angular Distributions ◽  
Reaction Products ◽  
Mixing Ratios ◽  
Absolute Intensities ◽  
Photographic Emulsions ◽  
Quantitative Explanation ◽  
Mev Protons

The 175Lu(p,α)172Yb reaction has been studied using beams of 17 MeV protons from the McMaster University tandem Van de Graaff accelerator. The alpha particle reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Levels up to an excitation energy of 2.8 MeV were studied with a resolution of 20 keV FWHM. The spin 3, 4, 5, and 6 members of the Kπ = 3+ band at 1172 keV were populated appreciably, indicating the existence of a significant two-quasiproton admixture in this band. The measured angular distributions and relative intensities within the band are consistent only with a Kπ = 3+, {7/2+ [404] − 1/2+ [411]} configuration for this admixture, and the absolute intensities indicate that it makes up (27 ± 10)% of the state. This observation provides a quantitative explanation for the observed magnetic moment of the 1172 keV level and also for the observed E2–M1 mixing ratios within the band. It may also be important in the explanation of other anomalous properties of this band. The present measurements also show large Kπ = 3+, {7/2+ [404] − 1/2+ [411]} admixtures in the previously assigned Kπ = 2+ band at 1609 keV and the Kπ = 3+ band at 1663 keV. In addition, the assignment of the 2073 and 2192 keV levels as Iπ = 4+ and 5+ members of a Kπ = 4+, {7/2+ [404] + 1/2+[411]} band has been confirmed.

Nuclear Reaction Studies of 151Sm

1973 ◽  
Vol 51 (18) ◽  
pp. 2000-2022 ◽  
Author(s):  
D. E. Nelson ◽  
D. G. Burke ◽  
J. C. Waddington ◽  
W. B. Cook
Keyword(s):  
Cross Sections ◽  
Coulomb Excitation ◽  
Negative Parity ◽  
Angular Distributions ◽  
Neutron Transfer ◽  
Reaction Products ◽  
Single Neutron ◽  
Nilsson Model ◽  
Nuclear Levels ◽  
Photographic Emulsions

Properties of nuclear levels in 151Sm have been studied by measuring angular distributions for the 152Sm(d,t)151Sm reaction and spectra at several angles for the 152Sm(3He,α)151Sm and 150Sm(d,p)151Sm reactions. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Transfer l values were deduced from the (d,t) angular distributions and from the ratios of (3He,α) and (d,t) cross sections. The (d,t), (d,p), and (3He,α) reactions on targets of 151Sm were also studied in order to learn more about the wave function of the 151Sm ground state. The low-lying positive parity levels can be described by the Nilsson model with Coriolis and ΔN = 2 interactions included. However, the properties of the low energy negative parity states could not be explained as easily. No mixture of Nilsson states was found which could simultaneously explain the single neutron transfer intensities and the Coulomb excitation probabilities from previous measurements.

The nuclear structure of 166Er

1979 ◽  
Vol 57 (11) ◽  
pp. 1999-2025 ◽  
Author(s):  
J. D. Panar ◽  
D. G. Burke
Keyword(s):  
Proton Transfer ◽  
Excitation Energy ◽  
Ground State ◽  
Transfer Reactions ◽  
Angular Distributions ◽  
Neutron Transfer ◽  
Reaction Products ◽  
Proton Transfer Reactions ◽  
Photographic Emulsions ◽  
Transfer Study

Two-quasiparticle states in 166Er have been studied using the 167Er(d,t)166Er, 167Er(3He.α)166Er, 165Ho(3He,d)166Er, and 165Ho(α,t)166Er reactions. Beams of 15 MeV deuterons, 24 MeV 3He2+, and 27 MeV 4He2+ particles were produced by the McMaster University tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge split-pole magnetic spectrograph and detected with photographic emulsions. Angular distributions were obtained for the (d,t) and (3He,d) reactions for levels up to ~2700 keV in excitation energy, although selected peaks were investigated at somewhat higher energies. The interpretation of the data was performed within the framework of the Unified model, incorporating pairing effects. In the neutron transfer study, two-quasiparticle states formed by removing a particle from the predominantly 7/2+[633] 167Er ground state were investigated, whereas the proton transfer study dealt with two-quasiparticle states formed by adding a particle to the 7/2−[523] ground state of 165Ho. Several previous assignments have been supported and many new ones are proposed. Several other assignments proposed in an earlier proton transfer study have been found to be incorrect. Earlier observations that some levels were populated in both the neutron transfer and proton transfer reactions have been confirmed and extended. In addition, the observation in the (d,t) reaction of several states populated by l = 0 neutron transfers has been interpreted in terms of a complex mixing scheme involving the 7/2+[633] ± 1/2+[400] configurations.

A Study of Levels in 149Nd using the (d, t) and (3He, α) Reactions

1973 ◽  
Vol 51 (4) ◽  
pp. 455-464 ◽  
Author(s):  
D. G. Burke ◽  
J. C. Waddington ◽  
D. E. Nelson ◽  
J. Buckley
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
State Transition ◽  
Angular Distributions ◽  
Ground State Transition ◽  
Reaction Products ◽  
Q Value ◽  
Nilsson Model ◽  
Photographic Emulsions ◽  
Peak Widths

Triton spectra from the 150Nd(d, t)149Nd reaction have been measured at 15 angles using beams of 12 MeV deuterons. The 150Nd(3He, α)149Nd reaction was studied at four angles with 24 MeV 3He beams. In all cases the reaction products were analyzed with an Enge-type magnetic spectrograph and detected with photographic emulsions. The peak widths (FWHM) were approximately 8 keV for the (d, t) studies and 25 keV for the (3He, α) spectra. It is now evident that the highest energy triton group ascribed to the 150Nd(d, t)149Nd reaction in previous works does not correspond to the ground state transition. According to the current interpretation the ground state transition has a Q value of −1.122 ± 0.010 MeV. The (d, t) angular distributions and the ratios of (3He, α) and (d, t) cross sections at selected angles were used to determine l values for a number of the transitions. Three states in 149Nd at 481, 813, and 986 keV are definitely populated by l = 0 transitions and thus have Iπ = 1/2+. A strongly perturbed band consisting of a mixture of Nilsson states from the i13/2 shell has been found, with properties similar to the corresponding bands in the isotones 151Sm and 153Gd. The total observed intensity for each of the l values 0, 1, 2, and 6 cannot be explained by the extreme single-particle shell model but is consistent with that predicted by the Nilsson model. However, the splitting of the strength among the observed states cannot be explained by the basic Nilsson model.

A Study of Levels in 153Gd Using the (d,t) and (3He,α) Reactions

1973 ◽  
Vol 51 (22) ◽  
pp. 2354-2368 ◽  
Author(s):  
G. Løvhøiden ◽  
D. G. Burke
Keyword(s):  
Cross Sections ◽  
Negative Parity ◽  
Positive Parity ◽  
Angular Distributions ◽  
Reaction Products ◽  
Ground State Band ◽  
Intensity Pattern ◽  
Nilsson Model ◽  
State Band ◽  
Photographic Emulsions

Triton spectra from the 154Gd(d,t)153Gd reaction have been measured at 15 angles using a beam of 15 MeV deuterons. The 154Gd(3He,α)153Gd reaction was studied at 4 angles with a 24 MeV 3He beam. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected with photographic emulsions. The (d,t) angular distributions and ratios of the (3He,α) and (d,t) cross sections were used to determine l values for a number of transitions. Members of the strongly perturbed band consisting of a mixture of Nilsson states from the i13/2 shell have been populated. An attempt has been made to describe some of the positive parity states in terms of the Nilsson model with Coriolis and ΔN = 2 mixings included. As spin assignments are now available for a large number of positive parity levels, it is possible to see a better developed pattern for this mixing than was presented previously. Although the observed intensity pattern for the 3/2−[521] ground-state band agrees with expectations, the remaining negative parity states cannot be easily explained in terms of the basic Nilsson model.

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