Structure of positive parity states in 29P and two-step processes in (p,t) reactions

From a study of (p,t) reactions on ³¹P and ³⁰Si it is suggested that in ²⁹P the states with $\text{J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}_1{}^{\mathrm{+}}$ and $\text{1}\text{2}{}_2{}^{\mathrm{+}}$, the pair $\text{3}\text{2}{}_2{}^{\mathrm{+}}$, $\text{5}\text{2}{}_1{}^{\mathrm{+}}$, and the pair $\text{7}\text{2}{}_3{}^{\mathrm{+}}$, $\text{9}\text{2}{}_1{}^{\mathrm{+}}$ are related by weak coupling of a s${}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ proton with the states 0₁⁺, 0₂⁺, 2₁⁺ and 4₁⁺ respectively of ²⁸Si. Completely atypical L = 2 angular distributions have been obtained for the $\text{3}\text{2}{}_1{}^{\mathrm{+}}$ and $\text{5}\text{2}{}_2{}^{\mathrm{+}}$ states in ²⁹P and it is suggested that this is due to contribution by two-step processes.     

The 152,154Eu(t, α) reactions: Studies of the 112[505] bands in 151Sm and 153Sm

Radioactive targets of ¹⁵²Eu(13 y) and ¹⁵⁴Eu(8.5 y) have been used to study the ^152,154 Eu(t, α)^151,153Sm reactions at an incident triton energy of 16 MeV. In these studies, we have identified the bandhead and three excited rotational states of the $\text{11}\text{2}\text{[505]}$ neutron orbital in both the ^151,153Sm nuclei The angular distributions and relative intensities for states in this band in both ^151,153Sm are reproduced reasonably well by using DWBA calculations and by assuming strongly deformed single-particle wave functions. We have used our results and the results of other studies to determine the equilibrium prolate shapes of both ^151,153Sm when the odd-neutron quasiparticle occupies the $\text{11}\text{2}\text{[505]}$ orbital. We estimate $\text{β}{}_2\text{~ 0.26}\text{for}{}^{151}\text{Sm and}\text{β}{}_2\text{~ 0.3}\text{for}{}^{153}\text{Sm}$.     

Partial-wave analysis of the low-mass (π+π−p) system produced in K−p interactions at 4.2 GeV/c

A partial-wave analysis of the low-mass (π⁺π^?p) system produced in the reaction K^?p → K^?(π⁺π^?p) at 4.2 GeV/c incident momentum is performed in order to study the two (π⁺π^?p) enhancements around 1500 and 1700 MeV. It is found that the low-mass (π⁺π^?p) system can be described using the spin-parity states $\text{J}{}^{\mathrm{P}}\text{=}\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}$ and $\text{5}\text{2}{}^{\mathrm{+}}$ only. In the 1500 MeV region contributions are observed from the $\text{1}\text{2}{}^{\mathrm{+}}$ wave decaying into p? and the $\text{3}\text{2}{}^{\mathrm{?}}$ wave decaying into Δ⁺⁺π^?; in the 1700 MeV region contributions are found from the $\text{1}\text{2}{}^{\mathrm{+}}$ wave decaying into Δ⁺⁺π^?, the $\text{3}\text{2}{}^{\mathrm{?}}$ wave decaying into p?, and the $\text{5}\text{2}{}^{\mathrm{+}}$ wave decaying into p?.     

Evidence for a strongly deformed prolate shape at N = 87 from 154Eu and 152Eu(p,t) reactions

The (p, t) reaction on radioactive targets of ^152,154Eu has been used to study rotational states associated with the configuration in the transitional odd-odd ¹⁵²Eu and ¹⁵⁰Eu nuclei. Our studies yieldcompelling evidence that this configuration in ¹⁵⁰Eu has a prolate structure which is strongly deformed and occurs at excitation energy of 1224 keV.     

Single-proton states in 151Pm

The ${}^{152}\text{Sm}\text{(}\text{t}\text{, α)}{}^{151}\text{Pm}$ reaction was studied using 17 MeV polarized tritons from the tandem Van de Graaff accelerator at the Los Alamos Scientific Laboratory. The α-particles were analyzed using a Q3D magnetic spectrometer and detected with a helical-cathode position-sensitive counter. The overall resolution was ～ 18 keV FWHM. Measurements of the ¹⁵⁰Nd(³He, d)¹⁵¹Pm reaction were made using 24 MeV ³He beams from the McMaster University tandem accelerator. The deuteron spectra were analyzed with a magnetic spectrograph using photographic emulsions for detectors, yielding a resolution of ～ 13 keV FWHM. By comparing the measured angular distributions of ($\text{t}\text{, α}$) and (³He, d) cross sections and ($\text{t}\text{, α}$) analyzing powers with DWBA predictions it was possible to assign spins and parities to many levels. The present results confirm earlier assignments of rotational bands based on the low-lying $\text{5}\text{2}{}^{\mathrm{+}}\text{[413],}\text{5}\text{2}{}^{\mathrm{?}}\text{[532],}\text{3}\text{2}{}^{\mathrm{+}}\text{[411]}\text{and}\text{1}\text{2}{}^{\mathrm{+}}\text{[420]}$ orbitals. In addition, states at higher excitation have now been assigned to the $\text{1}\text{2}{}^{\mathrm{+}}\text{[411]}\text{and}\text{7}\text{2}{}^{\mathrm{+}}\text{[404]}$ orbitals, and members of the $\text{3}\text{2}{}^{\mathrm{+}}\text{[422],}\text{5}\text{2}{}^{\mathrm{+}}\text{[402],}\text{3}\text{2}{}^{\mathrm{?}}\text{[541]}\text{and}\text{7}\text{2}{}^{\mathrm{?}}\text{[523]}$ bands are tentatively proposed. The spectroscopic strengths can be explained reasonably well by the Nilsson model when pairing and Coriolis mixing effects are included.     

E0 transitions in 114,116,118Sn

Low-lying 0⁺ states have been excited in the (p, p′) reaction via the$\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ isobaric analog resonance in ^114,116Sn and in radioactive decay in ¹¹⁸Sn. From conversion electron measurements, values of $\text{X =}\text{B(}\text{EO}\text{;0}{}^{\mathrm{+}}\text{→ 0}{}_1{}^{\mathrm{+}}\text{)}\text{B(}\text{E}\text{2; 0}{}^{\mathrm{+}}\text{→2}{}_1{}^{\mathrm{+}}\text{)}$ are obtained from the 1953 keV state in ¹¹⁴Sn, 1757 and 2027 keV states in ¹¹⁶Sn and 1758 and 2056 keV states in ¹¹⁸Sn.     

(p,t) Reactions on odd-a nuclei and the weak-coupling core-excitation model

Excited $\text{7}\text{2}{}^{\mathrm{?}}$ states to which enhanced L = 0 (p, t) transitions are observed have been identified in ⁴¹Ca at 2958 keV and in ⁵⁷Co at 2611 keV. A comparison of these (p, t) transitions with those to the 0⁺ states in ⁴⁰Ca at 3353 keV and in ⁵⁸Ni at 2940 keV leads to the conclusion that these states are obtained by weak-coupling of a $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ particle and hole, respectively, to the excited 0⁺ states of the doubly even cores. It is suggested that these cases are examples of a rather general weak-coupling phenomenon.     

The five-nucleon system above the three-particle threshold

Compound nucleus states in ${}^5\text{Li}$ and ${}^5\text{He}$ have been investigated with the ${}^3\text{He(d,p)pt}$ and ${}^3\text{H(d,n)pt}$ three-particle reactions. The observed $\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}$ states (E_X≈20 MeV) can be understood, in analogy to the ground states of the A=5 system, by coupling a $\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ nucleon to the first 0⁺ excited state of ${}^4\text{He}$.     

High-resolution measurements of analogue states in 53Mn

Using a high-resolution proton beam, differential cross sections were measured for the ⁵²Cr(p, p) and ⁵²Cr(p, p') reactions at incident energies between 3.20 and 4.76 MeV. Spins, parities and partial widths were determined for all resonances observed. Two p-wave and two d-wave analogue states were identified in this energy region. Spectroscopic factors and Coulomb displacement energies were extracted for the analogue states. The width distributions were analyzed for $\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{1}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{and}\text{5}\text{2}{}^{\mathrm{+}}$ resonances. Proton strength functions were also deduced for each J^π value, and their proton energy dependence was discussed.     

The 154Eu(t,p) reaction: Some new systematics in the N = 90 spherical-deformed transition region

A radioactive target of ¹⁵⁴Eu(8.3y) has been used to study the ¹⁵⁴Eu(t, p)¹⁵⁶Eu reaction at an incident energy of 17 MeV. The bandhead and one rotational state of the configuration have been identified in ¹⁵⁶Eu. The excitation energy of the 3^? bandhead is determined to be 448 ± 15 keV. The angular distribution of the first excited rotational state is anamolous and may indicate evidence for a strong two-step component in the reaction mechanism. The energy systematics of the Eu-Sm transition region are also investigated. We find that the systematics of $\text{h}\text{?}{}^2\text{2}\text{I}$ suggest that at N = 87 the ¹⁵⁰Eu excited configurations has a significantly more stable deformed structure than the corresponding $\text{11}\text{2}\text{[505]}$ one-quasiparticle structure in ¹⁴⁹Sm.     

Gamma decay of particle-core states in 209Pb

A γ-decay scheme for levels in ²⁰⁹Pb up to 4.13 MeV of excitation has been established by means of the reaction ²⁰⁸Pb(d, pγ)²⁰⁹Pb. In high efficiency p-γ coincidence measurements γ-cascades have been observed from the single-particle states and from core-excited states with very small single-particle strength. Assuming a qualitative validity of the weak-coupling model spins and main configurations of particle-core states can be deduced from their γ-decay. The $\text{J}{}^{\mathrm{\pi }}\text{= (}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{5}\text{2}{}^{\mathrm{?}}\text{or}\text{7}\text{2}{}^{\mathrm{?}}\text{,}\text{11}\text{2}{}^{\mathrm{?}}\text{,}\text{15}\text{2}{}^{\mathrm{?}}\text{)}$ members of the $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{?3}{}^{\mathrm{?}}$ multiplet could be located. A systematic manner of doublet splitting is found for the lowest states with main configuration $\text{(}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?1}}\text{?3}{}^{210}\text{Pb}\text{(0}{}^{\mathrm{+}}\text{, 2}{}^{\mathrm{+}}\text{, 4}{}^{\mathrm{+}}\text{, 6}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{)}$. A new decay branch of the $\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ single-particle state is attributed to an admixture of quadrupole core vibration.     

High spin states in 93mo populated in the (p,n) reaction

High spin states in the $\text{ν}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}{}^2$) multiplet in ⁹³Mo were investigated with the ⁹³Nb(p, n) ⁹³Mo reaction. A new isomeric state at 2430 keV with a half-life of 3.53±0.18 ns is interpreted as the lower $\text{17}\text{2}{}^{\mathrm{+}}$ member of the multiplet. A number of further states have been identified. The results are compared to previous experiments and shell model calculations.     

Investigation of level energies and B(E2) values for rotation-aligned bands in Hg isotopes

High spin states in ^{191, 192, 193, 195, 197, 199}Hg were investigated by observing γ-rays and conversion electrons in the compound reactions ${}^{\mathrm{192,\; 194,\; 198}}\text{Pt(α, x}\text{n}\text{)}\text{and}{}^{192}\text{Pt}\text{(}{}^3\text{He}\text{, 4}\text{n}\text{)}$. In ¹⁹⁷Hg the decoupled band built on the $\text{13}\text{2}{}^{\mathrm{+}}$ state and the semi-decoupled negative-parity band are observed up to $\text{I}{}^{\mathrm{\pi }}\text{=}\text{41}\text{2}{}^{\mathrm{+}}\text{and}\text{33}\text{2}{}^{\mathrm{?}}$, respectively. A careful investigation of ¹⁹⁹Hg revealed no new high spin states above the previously known levels with $\text{I}{}^{\mathrm{\pi }}\text{=}\text{25}\text{2}{}^{\mathrm{+}}\text{and}\text{31}\text{2}$^?. Half-lives were determined for the 10⁺, 7^?, 8^? and 16^? states in ¹⁹²Hg, the if$\text{33}\text{2}{}^{\mathrm{+}}$$\text{states in}{}^{\mathrm{191,193}}\text{Hg and the}$ (frc states in ^{191, 193, 195, 197}Hg. The systematics of the level energies and B(E2) values for the positive-parity ground and $\text{13}\text{2}{}^{\mathrm{+}}$ bands and the negative-parity semi-decoupled bands in ^190–200Hg is discussed.     

Nuclear reaction studies of 168Tm

The intrinsic structure of ¹⁶⁸Tm has been studied using the (³He, d) and (α, t) proton stripping reactions as well as the (d, t) and (³He, α) neutron pick-up reactions. The beams of 24 MeV ³He particles, 25 MeV α-particles and 12 MeV deuterons were obtained from the McMaster tandem Van de Graaff accelerator. The reaction products were analyzed with an Enge-type magnetic spectrograph and detected with photographic emulsions. The spectra have been interpreted in terms of the coupling of an odd proton and an odd neutron, each moving independently in a spheroidal potential, which gives rise to intrinsic two-quasiparticle states with $\text{K = ¦Ω}{}_1\text{±Ω}{}_2\text{¦}$. The identification of the intrinsic states was made by comparing the experimental cross-section patterns with those predicted with the aid of Coriolis coupling and distorted-wave Born approximation (DWBA) calculations. Rotational bands superimposed on the K^π = 3⁺ and $\text{K}{}^{\mathrm{\pi }}\text{= 4}{}^{\mathrm{+}}\text{, {}\text{7}\text{2}{}^{\mathrm{+}}\text{[633]}{}_{\mathrm{n}}\text{±}\text{1}\text{2}{}^{\mathrm{+}}\text{[411]}{}_{\mathrm{p}}\text{}}$ configurations, the first of which is the ground state, ha been observed in the spectra of all four reactions. New assignments have been made for configurations resulting from coupling the $\text{1}\text{2}$^? [541], $\text{7}\text{2}$⁺ [404], $\text{5}\text{4}$⁺ [402] and $\text{1}\text{2}$^? [530] p to the $\text{7}\text{2}$⁺ [633] neutron state. The neutron pick-up measurements confirmed the earlier assignments based on (d, t) reaction studies and suggested tentative assignments for the {$\text{1}\text{2}$⁺ [400]_n±$\text{1}\text{2}$⁺ [411]_p} and {$\text{3}\text{2}$⁺ [402]_n±$\text{1}\text{2}$⁺ [411]_p}     

The phase anomaly for elastic and inelastic scattering of the 19F + 12C system

The elastic and inelastic scattering of ¹²C from ¹⁹F leading to the $\text{1}\text{2}{}^{\mathrm{+}}\text{(}\text{gs}\text{),}\text{5}\text{2}{}^{\mathrm{+}}\text{(197}\text{keV}\text{),}\text{3}\text{2}{}^{\mathrm{+}}\text{(1.554}\text{MeV}\text{)}$ and $\text{9}\text{2}{}^{\mathrm{+}}\text{(2.780}\text{MeV}$) states has been studied at $\text{E(}{}^{12}\text{C}\text{)=30?60}\text{MeV}$. The angular distributions for the $\text{5}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}$ transitions are almost in phase with those of the elastic scattering and cannot be reproduced with the DWBA and CC caculation using collective form factors.     

High spin states in 57Co

High spin states of ⁵⁷Co have been studied via prompt γ-ray spectroscopy in the reactions ⁴⁸Ti(¹²C, p2n) and ⁵⁴Fe(α, p) at 26–48 MeV and 12–24 MeV, respectively. The energies and decay modes of these levels were determined from the analysis of γ-ray singles and γ-γ coincidence spectra, excitation functions, angular distributions and correlations. The relevant lifetimes were measured by the Doppler-shift attenuation method. The new levels established in this work are at 4037, 4814 and 5918 keV with the most probable J^π assignment of $\text{15}\text{2}{}^{\mathrm{?}}$, if $\text{17}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$, respectively. The previously known level at 2524 keV was assigned to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$. These together with the known $\text{9}\text{2}{}^{\mathrm{?}}$(1224 keV) and $\text{11}\text{2}{}^{\mathrm{?}}$(1690 keV) levels constitute the yrast states of ⁵⁷Co. The measured lifetimes of the above six levels are (in order of increasing energies) 0.085±0.030, 0.32±0.10, 0.16±0.06, 0.10_?0.07^+0.06, 1.5_?0.5⁴ and 0.17_?0.07^+0.08 ps, respectively. Comparisons with some theoretical calculations are presented.     

Spin assignments in 59Ni from the 58Ni(d, p)59Ni reaction

Angular distributions of the vector analyzing power and the absolute cross section were measured for the ⁵⁸Ni(d, p)⁵⁹Ni reaction at a deuteron energy of 10 MeV. The observed j-dependence of the vector analyzing power allowed unambiguous spin assignments for the following states in ⁵⁹Ni with excitation energies in $\text{MeV}\text{: 0.0,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 0.341,}\text{5}\text{2}{}^{\mathrm{?}}$; $\text{0.465,}\text{1}\text{2}{}^{\mathrm{?}}\text{; 0.879,}\text{3}\text{2}{}^{\mathrm{?}}$; $\text{1.303,}\text{1}\text{2}{}^{\mathrm{?}}\text{; 1.686,}\text{5}\text{2}{}^{\mathrm{?}}\text{; 3.454,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 3.858,}\text{3}\text{2}{}^{\mathrm{?}}\text{; 4.495,}\text{5}\text{2}{}^{\mathrm{+}}$. The data are well reproduced by DWBA calculations employing deuteron and proton optical model parameters obtained from analyses of elastic scattering cross sections and polarizations. A tentative spin assignment of $\text{9}\text{2}{}^{\mathrm{+}}$ is made for the level at 3.061 MeV. A $\text{5}\text{2}{}^{\mathrm{+}}$ assignment to the level at 3.538 MeV is suggested on the basis of the empirical behavior of the j-dependence of the vector analyzing power for l = 2 transitions. Measurements of the vector analyzing power for the four low-lying ⁵⁹Ni states formed by l = 1 transfer were made for angles from 2.5° to 15° using a magnetic spectrograph. A very strong j-dependence was observed for these far-forward-angle measurements in agreement with DWBA predictions.     

Study of stripping to levels of 21Ne

Angular distributions of the cross section and vector analyzing power have been measured for 8 levels in ²¹Ne using the ²⁰Ne($\text{d}$, p)²¹Ne reaction. New spin assignments are made to the 4.52 MeV level ($\text{J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}$) and the 5.69 MeV level ($\text{J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{?}}$). Our results support a $\text{J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}$ assignment to the 5.33 MeV level and disagree with the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}$ assignment to the 3.73 MeV level.     

Low-lying states in 95Tc studied with the 93Nb(α, 2nγ)95Tc reaction

Low-lying states in ⁹⁵Tc were studied with the ⁹³Nb(α, 2nγ)⁹⁵Tc reaction. The level scheme was obtained from the γ-γ coincidence measurement. The spin assignment was made on the basis of the observed γ-ray angular distributions and the excitation functions. The $\text{337}\text{keV}\text{7}\text{2}{}^{\mathrm{+}}\text{, 627}\text{keV}\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{), 882}\text{keV}\text{13}\text{2}{}^{\mathrm{+}}\text{and}\text{957}\text{keV}\text{11}\text{2}{}^{\mathrm{+}}$ states, and possibly state, are found to be strong candidates for the core multiplet states $\text{[(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>p</mtext>}}\text{?2}{}^{\mathrm{+}}\text{]}{}_{\mathrm{J}}$. These states are discussed in term of a weak coupling model and the dressed three-quasiparticle model. The observed γ-ray angular distributions are compared with expectations based on a simple deexcitation model of the (α, 2nγ) reaction.