Structural connections between 148Sm and 149Sm nuclei

The ^{146, 148}Nd(α, χn) and ^{148, 150}Nd(³He, χn) reactions at E_α = 20–43 MeV and E_3He = 19–27 MeV, are used to study excited states in the ¹⁴⁹Sm₈₆ and ¹⁴⁹Sm₈₇ nucleides and consequently the low-spin odd-parity excitation. The mixing ratios and multipolarities of the most prominent transitions are deduced from the combined evidence of angular distribution and electron conversion data. The spin-parity assignments for most of the levels observed are established. In ¹⁴⁸Sm the ground state band extending to I^π = 10⁺ is predominantly populated. A negative-parity odd-spin band extending from I^π = 3^?through 11^? is also observed. The bands in ¹⁴⁸Sm are interpreted within the framework of the interacting boson approximation model. In ¹⁴⁹Sm positive-parity levels with spin up to $\text{25}\text{2}$ and negative-parity levels with spins up to $\text{21}\text{2}$ are observed. The predominant γ-decay proceeds via transitions associated with $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$, $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$, $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ intrinsic configurations. The branching ratios B(E1)/B(E2) are calculated and compared in both ¹⁴⁸Sm and ¹⁴⁹Sm nucleides. The B(E1)/B(E2) dependence on the value of Z for some N = 86 (as well as 88 and 84) isotones showing a minimum of Z = 64 was noted. A 4 ns high-spin isomer mainly decaying into the positive-parity band based on the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ state in ¹⁴⁹Sm is found. Experimental evidence is presented to interprete the $\text{1}\text{2}{}^{\mathrm{+}}$, $\text{15}\text{2}{}^{\mathrm{+}}$, … and $\text{9}\text{2}{}^{\mathrm{?}}$, $\text{13}\text{2}{}^{\mathrm{?}}$, …, ΔI = 2, sequences in ¹⁴⁹Sm as arising from the coupling of an $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ neutron to the octupole and quadrupole modes of the ¹⁴⁸Sm core nucleus. The absolute reaction cross sections for the ^{146, 148, 150}Nd(³He, χn) reactions have been determined for different bombarding energies. The mixing of the $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ shells is discussed in the framework of an axial-particle-rotor model calculation.     

7 MeV dipole ground state transitions in 207Pb, 208Pb and 209Bi

The Doppler-broadened 7.117 MeV line from the ¹⁹F(p, αγ)¹⁶O reaction has been used to resonantly excite levels in ²⁰⁸Pb at 7071±2 and 7091±2 keV, in ²⁰⁷Pb at 7186±5 and 7206±5 keV and in ²⁰⁹Bi at 7179±5 and 7202±5 keV. On the basis of angular distribution measurements the 7071 and 7091 keV levels of ²⁰⁸Pb are assigned spins of 1 and assuming 100% ground state branching the widths are calculated to be 31±3 and 17±2 eV respectively. It is suggested that the states in ²⁰⁷Pb and ²⁰⁹Bi arise from the weak coupling of a $\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ neutron hole and an $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton respectively to one or the other of the ²⁰⁸Pb levels. The widths obtained in terms of _gΓ_o²/Γ are 15±4 and 25±5 eV for the 7186 and 7206 keV levels of ²⁰⁷Pb and 24±5 and 30±5 for the levels of ²⁰⁹Bi respectively. These values are consistent with the weak-coupling suggestion.     

12C(7Li,t)16O and stellar helium fusion

The reaction ¹²C(⁷Li, t)¹⁶O has been studied at $\text{E(}{}^7\text{Li}\text{) = 34}\text{MeV}$ with the LASL tandem accelerator and QDDD magnetic spectrometer. Angular distributions to levels with E_x < 11 MeV have been obtained from 0° to 90°, including 0°. The results have been analyzed with finite-range distorted-wave Born approximation theory. The α-particle spectroscopic factors and reduced widths obtained are compared with those calculated with group theory (SU(3)) and other models. The analysis of data for the 7.1 and 9.6 MeV J^π = 1^? levels, which are of great importance in stellar helium buring, yields a ratio, R, of dimensionless reduced α-widths $\text{θ}{}^2{}_{\mathrm{<mtext>a</mtext>}}\text{(7.1}\text{MeV}\text{)}\text{θ}{}^2{}_{\mathrm{<mtext>a</mtext>}}\text{(9.6}\text{MeV}\text{)}\text{= 0.35b ± 0.13}$. The observed line width of the 9.6 MeV level (Γ_c.m. = 390 ± 60 keV) is less than the accepted value (Γ_c.m. = 510 ± 60 keV) and implies θ²_a(9.6 MeV) ≈ 0.6. These results as well as data for the 6.92 MeV J^π = 2⁺ and 10.35 MeV J^π = 4⁺ “α-cluster” states indicate 0.09 < θ²_a(7.1 MeV) < 0.33 with a mean value θ²_a(7.1 MeV) = 0.14 ± 0.04. The implication for stellar helium burning is discussed.     

Internal bremsstrahlung in the electron capture decay of 145Sm

Internal bremsstrahlung (IB) emitted in the non-unique first-forbidden electron capture decay of the $\text{7}\text{2}{}^{\mathrm{?}}$ ground state of ¹⁴⁵Sm to the $\text{7}\text{2}{}^{\mathrm{+}}\text{61}\text{keV}$ first excited level of ¹⁴⁵Pm has been studied. The total IB spectrum and the IB spectrum for captures proceeding via the 1s shell were measured for photons in the energy range of 100–580 keV and the spectra were normalized to the non-radiative capture rate. The experimental data agree with theoretical predictions.     

Medium-spin levels and the character of the 20.4 ns 132+ isomer in 145Gd

Levels of the N = 81 nucleus ¹⁴⁵Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the ¹⁴⁴Sm(³He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin $\text{21}\text{2}{}^{\mathrm{+}}$, five other high-spin non-yrast states and a new 20.4 ns $\text{13}\text{2}$ isomer at 2200.2 keV in ¹⁴⁵Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the $\text{v}\text{h}{}^{\mathrm{?1}}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ state. We propose an octupole $\text{v}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{j}{}^{\mathrm{?2}}\text{× 3}{}^{\mathrm{?}}$ main configuration for the isomer, analogous to the 997 keV $\text{13}\text{2}{}^{\mathrm{+}}$ isomer in ¹⁴⁷Gd. The levels of ¹⁴⁵Gd are discussed on the basis of the spherical shell model.     

Ground-state α-decay of N = 128 isotones 216Ra, 217Ac and 218Th

The α-decay properties of very short-lived N = 128 isotones, ²¹⁶Ra, ²¹⁷Ac and ²¹⁸Th, were investigated by the pulsed-beam method. Alpha emitters of interest were produced in the bombardment of ²⁰⁸Pb or ²⁰⁹Bi with 65–96 MeV ¹²C or ¹⁴N ions and α-decays were measured between natural beam bursts of the cyclotron. The results obtained are _Eα = 9.349±0.008 MeVand $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 182±10}\text{ns for}{}^{216}\text{Ra}\text{, 9.650±0.010}\text{MeV}$ and $\text{111±7}\text{ns for}{}^{217}\text{Ac}\text{, 9.665±0.010}\text{MeV}$ and $\text{96±7}\text{ns for}{}^{218}\text{Th}$. The experimental reduced α-widths of N = 128 isotones from ²¹²Po to ²¹⁸Th are shown to agree well with the simple shell model calculation.     

Interference effects in 12C(p, γ)13N and direct capture to unbound states

Excitation functions of the capture reaction ¹²C(p, γ₀)¹³N have been obtained at θ_γ = 0° and 90° and E_p = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in ¹³N is included in the analysis in addition to the two well-known resonances in this beam energy range $\text{[E}{}_{\mathrm{p}}\text{= 457(}\text{1}\text{2}{}^{\mathrm{+}}\text{)}$ and 1699 $\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{) keV]}$. The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C²S(l = 1) = 0.49 ± 0.15 has been deduced for the $\text{1}\text{2}{}^{\mathrm{?}}$ ground state in ¹³N. Excitation functions for the reaction ${}^{12}\text{C(p,γ}{}_1\text{p}{}^1\text{)}{}^{12}\text{C}$ have been obtained at θ_γ = 0° and 90° and E_p = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. Above E_p = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below E_p = 1 MeV, i.e., E_p → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at $\text{E}{}_{\mathrm{p}}\text{? 1 MeV}$, a spectroscopic factor of C²S(l = 0) = 1.02 ± 0.15 has been found for the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. A search for direct capture transitions to the $\text{3512 (}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$and $\text{3547 (}\text{5}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound states resulted in upper limits of C²S(l = 1) ≦ 0.5 and C²S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the ¹²C(p, γ₀)¹³N reaction also is discussed.     

Recoil-distance lifetime measurements in 51Cr, 53Cr, 53Mn and 53Fe

Levels in ⁵¹Cr, ⁵³Cr, ⁵³Mn and ⁵³Fe were excited via (α, n) or (α, p) reactions. Using the recoil-distance method, mean-lives (in ps) have been obtained for excited states (keV) in the residual nuclei: ${}^{51}\text{Cr}\text{(2256) = 66±2,}{}^{53}\text{Cr}\text{(1536) = 21.5±3.5,}{}^{53}\text{Cr}\text{(2173) = 6.7±3.1,}{}^{53}\text{Mn}\text{(2564) = 20}{}^{\mathrm{+8}}{}_{\mathrm{?6}}\text{and}{}^{53}\text{Fe}\text{(1424) = 4.0±1.0}$. Reduced transition probabilities calculated from these values are compared with the available theoretical values.     

A study of some resonances in the 54Fe(p, γ)55Co reaction

Excitation functions for the ⁵⁴Fe(p, γ)⁵⁵Co reaction have been recorded in the energy region E_p = 1100–1760 keV. The decay schemes and branching ratios of ten resonances have been investigated. Angular distributions of primary γ-rays have been measured for three resonances to establish resonance spins. Resonance strengths for six resonances and gamma widths for three resonances have been determined. The isobaric analogues of the ground ($\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{?}}\text{)}\text{and}\text{1919}\text{keV}$$\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}$^?) states of the parent nucleus ⁵⁵Fe have been identified at 4722 and 6712 keV respectively in ⁵⁵Co. The Coulomb displacement energies of the observed analogue pairs (0–4722 keV) and (1919–6712 keV) have been obtained. The strengths of the possible analogue-antianalogue transitions for the proton capture state at E_p = 1679 keV have also been determined.     

The M1 strength distribution in the γ-decay of the gcase92 analogue state in 61Cu

The γ-decay of 26 resonances in the reaction ⁶⁰Ni(p, γ)⁶¹Cu in the range E_p = 3690–3790 keV has been investigated. The $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ isobaric analogue state (IAS) corresponding to the parent state at $\text{E}{}^1\text{= 2114}\text{keV}$ in ⁶¹Mi has been resolved into several fine structure components. The absolute strength for the transition to the antianalogue state is found to be Γ_γ = 0.24 ± 0.07 W.u. The measured M1 strength distribution for the decay of the $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$. IAS is compared to theoretical predictions.     

Alpha-decay widths in 20Ne

The α-decay of several unbound levels in ²⁰Ne has been studied by ¹⁶O(α, α) elastic and inelastic scattering. A narrow resonance, Γ_c.m. = 13±4 eV, with J^π = 5^? was found at $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{(}{}^{20}\text{Ne}\text{) = 8.451±0.005}\text{MeV}$ and is associated with the lowest K = 2^? quasirotational band. Several new, narrow resonances were found between E_x = 16.0?18.4 MeV. Reduced α-decay widths have been obtained for the lowest K = 0⁺, 2^? and 0^?bands. For states described predominantly by the (8, 2) representation of SU(3) we note a reduction of the reduced widths with increasing spin. Reduced widths of positive parity bands are reviewed.     

Parity non-conservation in the radiative capture of polarized neutrons by 35Cl

We report a measurement of the forward-backward asymmetry in the radiative capture of polarized cold neutrons in the reaction ³⁵Cl(n, γ)³⁶Cl where ³⁶Cl is in the ground state. The measured value of the asymmetry is a = (1.57 ± 0.531) × 10^?4. We deduce the mixing between the 2⁺ capture level and the neighboring 2^? levelto be $\text{〈2}{}^{\mathrm{?}}\text{¦H}{}_{\mathrm{<mtext>p.v.</mtext>}}\text{¦2}{}^{\mathrm{+}}\text{〉 = ?0.25 ± 0.08}\text{eV}$ before corrections. A measurement of the integral asymmetry of all γ-rays in the neutron capture by ³⁵Cl leads to agreement with measurements at Leningrad.     

Nuclear orientation study of the excited states of 129I populated in the decay of 129gTe and 129mTe

From the angular distributions of γ-rays emitted by oriented ^129gTe and ^129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of ¹²⁹I at 487.4 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$, 696.0 keV $\text{(}\text{11}\text{2}{}^{\mathrm{+}}\text{)}$, 729.6 keV $\text{(}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$, 768.9 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$, 1050.4 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$ and 1111.8 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$. In addition, E2/M1 amplitude ratios for the following ¹²⁹I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076^+0.037_?0.148); δ(487.4) = 0.50^+0.17_?0.10 or δ^? = 0.35^+0.15_?0.09; δ(556.7) = 0.06±0.02 or δ^? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ^? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ^?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ^?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ^?1 =0.20±0.03 if $\text{I}{}^{\mathrm{\pi }}\text{(845}\text{keV}\text{) =}\text{7}\text{2}{}^{\mathrm{+}}$; δ(1022.6) = ?(0.02 ±0.02) or δ^?1 = ?(0.23±0.02); $\text{δ(1084) = 0.56}{}^{\mathrm{+0.04}}{}_{\mathrm{?0.14}}$; δ(1111.8) = 0.06±0.05 or δ^?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes $\text{1}\text{2}{}^{\mathrm{+}}$ as a possible spin assignment for the 559.6 keV level, so that no $\text{1}\text{2}{}^{\mathrm{+}}$ level is fed in the decay from ¹²⁹Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model.     

Coulomb excitation of 85Rb and 87Rb

Energy levels of ⁸⁵Rb and ⁸⁷Rb have been studied via de-excitation γ-rays following Coulomb excitation with ³⁵Cl ions. In addition to the known negative-parity states at 151.2 keV and 868.2 keV in ⁸⁵Rb, two states at 281.0 keV and 731.8 keV have been found with fourγ-ray transitions of 129.8, 281.0, 450.8 and 731.8 keV. Only one Coulomb excited state at 402.6 keV in ⁸⁷Rb has been observed. The B(E2↑) values (in units e² · b²) have been determined as 0.0035±0.0004 (151.2 keV), 0.0016±0.0002 (281.0 keV), 0.0101 ±0.0010 (731.8 keV), and 0.036±0.004 (868.2 keV) for the states in ⁸⁵Rb, and as 0.0054±0.0006 (402.6 keV) for the state in ⁸⁷Rb. The mean lifetimes of the 731.8 keV and 868.2 keV states have been measured by the Doppler shift attenuation method as 6.4±0.7 psec and 4.2±0.5 psec respectively. Angular distribution measurements allow unique spin and parity assignments of $\text{1}\text{2}{}^{\mathrm{?}}$ and $\text{3}\text{2}{}^{\mathrm{?}}$ to the 281.0 keV and 731.8 keV levels respectively. The spin and parity of the 868.2 keV level has been restricted to $\text{5}\text{2}{}^{\mathrm{?}}$ or $\text{7}\text{2}{}^{\mathrm{?}}$.     

Negative-parity states in Pb isotopes: g-factor of the 480 ns,if Jπ = 9− isomer in 200Pb

The g-factor of the 480 ns, 9^? isomer at 2.237 MeV in ²⁰⁰Pb was measured by the time-differential perturbed angular distribution method. The result, g = ?0.0285±0.0011 confirms the rather pure $\text{(}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)}$ quasiparticle structure of this state. Half-lives of 480±20 ns, 43±3 ns and 42±4 ns have been measured for the 2237 keV 9^?, 2154 keV 7^? states in ²⁰⁰Pb and the 2208 keV state in ²⁰²Pb, respectively; E2 transitions and g-factors of negative-parity states in even, neutron-deficient Pb isotopes are discussed.     

The 153Sm nucleus: An experimental and theoretical study

The level structure of ¹⁵³Sm has been studied by means of the ¹⁵⁰Nd(α, n)¹⁵³Sm reaction. The experiment included measurements of the γ-γ coincidences and γ-ray yield as a function of projectile energy. The rotational band built on the $\text{11}\text{2}{}^{\mathrm{?}}$[505] Nilsson orbital was observed up to spin $\text{19}\text{2}$, and two ΔI = 2 bands of positive parity were identified with spins up to $\text{19}\text{2}\text{and}\text{21}\text{2}$, respectively. These bands are associated with the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ single-particle structure.The data obtained in the present work together with data available in the literature are compared to the result of a particle-rotor coupling calculation. The ¹⁵³Sm nucleus is found to be a wellbehaved rotor. An appropriate single-particle level scheme for ¹⁵³Sm is established.     

The (n, 2n) cross sections of 85Rb, 87Rb and 144Sm

The (n, 2n) cross sections at neutron energies between 14.9 and 17.0 MeV have been measured for ⁸⁵Rb, ⁸⁷Rb and ¹⁴⁴Sm by the mixed-powder method and γ-ray detection by a Ge(Li) spectrometer. Using the ²⁷Al(n, α)²⁴Na reaction for monitoring, the measured cross sections were (in mb): ${}^{85}\text{Rb}\text{(}\text{n}\text{, 2}\text{n}\text{)}{}^{\mathrm{<mtext>84(</mtext><mtext>m+g</mtext><mtext>)</mtext>}}\text{Rb}\text{, 1125±141, 1177±148}\text{and}\text{1235±162}\text{at}\text{15.0±0.4}\text{MeV}\text{, 16.2±0.7}\text{MeV and}\text{17.0±0.9}\text{MeV, respectively}\text{;}{}^{85}\text{Rb}\text{(}\text{n}\text{, 2}\text{n}\text{)}{}^{\mathrm{<mtext>84</mtext><mtext>m</mtext>}}\text{Rb}\text{, 662±83, 688±87}\text{and}\text{765±99}\text{at}\text{15.0±0.4}\text{MeV}\text{, 16.2±0.7}\text{MeV and}\text{17.0±0.9}\text{MeV}\text{,}\text{respectively}\text{;}{}^{87}\text{Rb}\text{(}\text{n}\text{, 2}\text{n}\text{)}{}^{\mathrm{<mtext>86(</mtext><mtext>m+g</mtext><mtext>)</mtext>}}\text{Rb}\text{, 1336±168}\text{and}\text{1301±162}\text{at}\text{15.0±0.4}\text{MeV and}\text{16.2±0.7}\text{MeV respectively}\text{;}{}^{144}\text{Sm}\text{(}\text{n}\text{, 2}\text{n}\text{)}{}^{\mathrm{<mtext>143(</mtext><mtext>m+g</mtext><mtext>)</mtext>}}\text{Sm}\text{, 1202±130, 1300±141, 1516±179}\text{and}\text{1514±179}\text{at}\text{14.9±0.3}\text{MeV}\text{, 15.5±0.3}\text{MeV}\text{, 16.4±0.5}\text{MeV and}\text{16.7±0.2}\text{MeV, respectively}$. The measured values are compared with the statistical model calculations of Pearlstein.     

Lifetime and g-factor results for the 132− 1985 keV level in 91Nb and the 152− 2288 keV level in 91Zr

Lifetime and g-factor measurements have been made with pulsed beam-γ time-differential techniques using the ⁸⁹Y(α, 2n)⁹¹Nb and ⁸⁸Sr(α, n)⁹¹Zr reactions. A mean lifetime τ = 14.4 ± 0.5 nsec and a g-factor of 1.26 ± 0.04 were obtained for the $\text{13}\text{2}{}^{\mathrm{?}}$ 1985 keV level in ⁹¹Nb and τ = 41.9 ± 1.2 nsec and g = 0.70 ± 0.01 were obtained for the $\text{15}\text{2}{}^{\mathrm{?}}$ 2288 keV level in ⁹¹Zr. These results are compared to theoretical calculations for $\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^2\text{(π}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ and $\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)(π}\text{p}\text{1}\text{2}\text{)(v}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ configurations in ⁹¹Nb and ⁹¹Zr, respectively.     

A study of 3He capture in light nuclei

Excitation functions at θ = 90° have been measured for ${}^{16}\text{O}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0?2,\; 3?5,\; 6}}\text{)}{}^{19}\text{Ne}$, ${}^{15}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1?4}}\text{)}{}^{18}\text{F}\text{,}{}^{14}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1,2,3}}\text{)}{}^{17}\text{F}$, and ${}^{20}\text{Ne}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^{23}\text{Mg}$, in the range E_{3He = 3–19 MeV}. The first reaction has also been studied at θ = 40°. Excitation functions at 90° have also been measured for and ${}^4\text{He}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^7\text{Be}$ for E_3He = 19–26 MeV. Angular distributions have been measured for the first four reactions.For the most excitation functions, a broad peak is observed, several MeV wide, centred at about E_x≈ 20 MeV. Superimposed on this, in some cases, are narrower peaks, with width ≈ 1 MeV. Energies and widths have been extracted for all resonances.Cluster-model calculations have been carried out, using methods similar to those which have proved successful for low-lying states in A= 18–19 nuclei. No satisfactory correspondence with the present results was found. The shell model has been used to calculate Γ_3He and Γ_γ for 1?ω excitations in the final nuclei. These generally show good agreement with the trends of the experimental data. The results are consistent with the excitation of the giant dipole resonance in ³He capture, but much more weakly than in proton capture.     

In-beam study of 144Gd

A level scheme of ¹⁴⁴Gd has been established using the ¹⁴⁴Sm(α, 4nγ) reaction and in-beam spectroscopy methods. Excitation functions, γ-ray angular distributions, γ-γ coincidence spectra, γ-spectra time related to the cyclotron beam bursts and conversion coefficients for the delayed transitions have been measured.The level scheme comprises 11 levels with spins up to I = 12. Two isomers, a 13 ± 2 ns, 7^? state at 2471.4 keV and a 145 ± 30 ns, 10⁺ state at 3433.0 keV have been observed. The former has similar excitation energy as the 7^? isomers in ¹⁴²Sm, ¹⁴⁰Nd and ¹³⁸Ce and it may arise from the $\text{{ν}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{× ν}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{}}$ configuration although its lifetime seems to indicate some degree of collectivity. The 10⁺ state has a similar excitation energy as the 10⁺ isomer found in ¹³⁸Ce and it may arise from the dominant $\text{ν}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}{}^{\mathrm{?2}}$ configuration. Below the 10⁺ isomer in ¹⁴⁴Gd only two excited states have positive parity; the hitherto known first 2⁺ and 4⁺ states. The 11⁺ and 12⁺ states must include four-particle configurations or they have to be of collective nature. The latter possibility is supported by the considerable E2/M1 mixture (≈ 20 %) observed for the 11⁺ to 10⁺ transition. An analysis of the systematics of ground band levels in the N = 80 isotones shows the same gradual behavior between the two VMI solutions previously found for the Te isotopes.