Electromagnetic properties of levels in 55Mn

Excited levels of ⁵⁵Mn were produced by the reaction ⁵²Cr(α, p) at 10.5 and 11.1 MeV beam energy. A series of γ-ray measurements was made, all in coincidence with protons detected near 180°. A Ge(Li) γ-ray detector was used at 4 angles, and extensive angular-correlation measurements were made with an array of NaI(Tl) detectors. Excitation energies of 25 levels up to 3161 keV were determined, including a new level at 2215 keV. Only the level at 2285 keV and the $\text{1}\text{2}{}^{\mathrm{?}}$ state near 1290 keV were not observed in this range. From Doppler-shift attenuations, the mean lifetimes of 14 levels up to 2565 keV were deduced. Branching ratios and multipole mixing ratios were obtained for most of these levels. The following spin assignments were determined: 1530 keV, $\text{J =}\text{3}\text{2}$; 1885 keV, $\text{J =}\text{7}\text{2}$ or $\text{5}\text{2}$; 2565 keV, $\text{J =}\text{3}\text{2}$. Reduced transition probabilities, B (M1) and B (E2), of many transitions were calculated from these experimental results and are compared with the available theoretical values.     

Gamma-ray spectroscopy of 66Zn and 67Zn and the role of the g92 orbital

Measurements of γ-ray yield functions, γ-γ coincidence spectra and y-ray angular distributions following the ⁶⁴Ni(α, n) and (α, 2n) reactions have been made. Beam energies of 17 to 25 MeV were used. Among the new levels observed, with their proposed spin-parity assignments, are: in ⁶⁶Zn, 3708 keV, (5)⁺; 3896 keV, 5^?; 4812 keV, (7^?); 5110 keV, (8^?); 6417 keV; (10^?); 7516 keV, (12⁺); and in ⁶⁷Zn, 2937 keV, $\text{13}\text{2}{}^{\mathrm{+}}$; 3491 keV, $\text{17}\text{2}$ or $\text{19}\text{2}$; 3492 keV, ($\text{13}\text{2}$(si+)); 4221 keV, ($\text{19}\text{2}$^?); 4631 keV, ($\text{21}\text{2}{}^{\mathrm{+}}$); 4685 keV, ($\text{21}\text{2}$^?). Comparison between the ground-state sequence, 0⁺ to 6⁺, in ⁶⁶Zn and the first $\text{9}\text{2}$⁺ to $\text{21}\text{2}$⁺ levels in ⁶⁷Zn strongly suggests that the latter be described as a g_{$\text{9}\text{1}$} neutron orbital weakly coupled to the ⁶⁶Zn core. Other sequences of high-spin ⁶⁶Zn states are proposed to be formed from two-quasiparticle states containing the g_{$\text{9}\text{2}$} excitation, coupled to the same ground-state sequence.     

Electromagnetic transitions in 51Mn

The nuclear structure of ⁵¹₂₅Mn was studied by γ-ray spectroscopy in the ⁵⁴Fe(p, α)⁵¹ Mn reaction (E_p = 9.0–13.2 MeV) and the ¹⁴N+³⁹K, ¹⁶O+⁴⁰Ca and ¹⁴N+⁴⁰Ca fusion-evaporation reactions (E_beam = 36 MeV). In the ⁵⁴Fe(p, αγ)⁵¹Mn reaction γ-rays were detected in coincidence with α-particles emitted near 180°; mean lifetimes and γ-ray mixing and branching ratios were deduced from Doppler shift attenuation and α-γ angular correlation measurements, respectively. Definite spin assignments are: 237 and 2416 keV, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{?}}$; 1140 keV, $\text{9}\text{2}$^?; 1488 keV, $\text{11}\text{2}$^?; 1825 and 2140 keV, $\text{3}\text{2}$^?. The results for other states below 3 MeV are consistent with the existence of rotational bands (/kh²/2/OI/t~ 95 keV) built on the ($\text{3}\text{2}$⁺) 1817 keV and $\text{1}\text{2}$⁺ 2276 keV hole states. The various measurements together with an earlier value for the lifetime of the first-excited state determine unambiguously the B(M1) and B(E2) values for all of the decay branches of the $\text{7}\text{2}$^?, $\text{9}\text{2}$^? and $\text{11}\text{2}$^? lowest three excited states. From the γ-singles and γ-γ coincidence observations with fusion-evaporation reactions, the yrast cascade proceeds through these three states and higher states at 2957, 3250,3680 and 4139 keV which are suggested to have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{?}}$, $\text{15}\text{2}$^?,$\text{15}\text{2}$^? and $\text{19}\text{2}$^?, respectively. The various experimental results for the $\text{5}\text{2}$^? → ($\text{19}\text{2}$^?) yrast states are in good overall agreement with shell-model calculations in the (f_{$\text{7}\text{2}$}¹ space.     

Low-lying levels in 120Sb studied with the 120Sn(p,nγ) reaction

Properties of the levels in ¹²⁰Sb have been studied with the reaction ¹²⁰Sn(p, nγ). The low-lying level scheme of ¹²⁰Sb below 450 keV was constructed from the γ-ray excitation functions and γ-γ coincidences. The spins and parities were assigned from comparisons of the measured angular distributions and linear polarizations of the deexciting γ-rays as well as the absolute excitation functions of the residual levels with the predictions of the statistical compound nucleus model. In addition, the half-life of an isomeric state at 78.15 keV was measured. The results are 8.37 keV, 2^?; 78.15 keV, 3⁺; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 241±3}\text{ns}$; 149.29 keV, 3⁺; 166.05 keV, 3^?; 192.64 keV, 2⁺; 233.06 keV, 2⁺; 243.80 keV, 4; 260.29 keV, 3^?; 261.68 keV, 4; 334.07 keV, 4; 341.14 keV, 5; 343.21 keV, 4; 390.31 keV, 2 or 3⁺; 437.68 keV, 1 or 2 and 447.68 keV, 1⁽⁺⁾.     

Beta decay studies in the vicinity of 13250Sn82: Excited states in 13051Sb, 13052Te and 13252Te

Using the OSIRIS on-line isotope separator facility, the decays of ¹³⁰Sn and ^{130, 132}Sb have been studied. On the basis of singles γ and γ-γ coincidence Ge(Li) spectra and conversion electron Si(Li) measurements, level schemes for ¹³⁰Sb, ¹³⁰Te and ¹³²Te have been constructed. The corresponding half-lives have been measured using multiscaling technique. The 3.8 min ground state of ¹³⁰Sn populates only positive parity states in the πν^?3 nucleus ¹³⁰Sb: the energetically lowest 5⁺ state with the $\text{(π1}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{, ν2}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ configuration assignment; the $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 3.6 ± 0.3}\text{ns}\text{4}{}^{\mathrm{+}}$ state at 70.0 keV; the 2⁺ state at 262.5 keV; the (0, 1)⁺ state at 697.2 keV; the 3⁺ state at 813.1 keV and the 1⁺ state at 1042.3 keV excitation energy. A 1.7 min isomeric state in ¹³⁰Sn, with the tentative spin assignment (7^?), populates several odd parity levels in ¹³⁰Sb. These arise from the $\text{(π1}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{, ν1}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}{}^{-1}\text{)}$ and/or $\text{(π2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{, ν1}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}{}^{-1}\text{)}$ configurations and are located 84.7 keV (6^?), 144.9 keV (7^?), 688.5 keV and 1044.0 keV above the 40 min 8^? β- decaying state. No transitions between odd and even parity states have been observed.The most important excited states in ¹³⁰Te found in the β^? decay of the 6.6 min ¹³⁰Sb 5⁺ state are: 839.4 keV, 2⁺; 1632.8 keV, 4⁺; 1815.1 keV, 6⁺; 2100.8 keV, 5^?.Levels in the π²ν^?2 nucleus ¹³²Te were observed in the β^? decays of the 2.8 min ¹³²Sb (4⁺) and the 4.2 min ¹³²Sb (8^?) states. Unique spin and parity assignments have been given to the following states: 973.9 keV, 2⁺; 1670.7 keV, 4⁺; 1774.1 keV, 6⁺; 1924.7 keV, 7^?; 2053.0 keV, 5^?.     

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.     

Level structure of 76Br from the 75As(α,3nγ) reaction

Hitherto unknown states of ⁷⁶Br were excited through the (α, 3nγ) reaction on ⁷⁵As at E_α = 30 to 55 MeV. Excitation functions, γ-ray angular distributions, γ-γ coincidences and the γ-ray emission time with respect to the beam bursts were determined. Levels above the 1^? ground state at energies (in keV) with the following spin-parity assignments are proposed: 141.8, 2; 253.7, 3^?; 491.8, 4; 584.9, 5^?; 1016.3, 6. These levels exhibit the energy spacings of a Coriolis-perturbed rotational band and the branching ratios show collective behavior. The comparison of these levels with those of the $\text{5}\text{2}$⁺ ground-state band recently reported in ⁷⁷Kr show that (a) the Coriolis effects are quite similar and (b) the first two excited levels lie very close in energy in both cases. The possibility that these two facts indicate the validity of the rotation aligned coupling scheme in a doubly odd system is discussed.     

Spectroscopic investigations of the decay 223Ra → 219Rn

Internal conversion electron spectra of the transitions 4.4 keV, 10.0 keV, 14.4 keV, and 324.1 keV in the decay ²²³Ra → ²¹⁹Rn were measured. E2/M1 mixing ratios of these γ-transitions were deduced from conversion electron intensity ratios: δ² = 3.8(4) · 10^?3, 2.35(18) · 10^?3, 12.85(36) · 10^?3, 0.23(3). The half-lives of the 4.4 keV and 14.4 keV levels were determined as $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 15.4(1.3)}$ nsec and 0.875(30) nsec. Reduced transition probabilities were calculated and compared to the Weisskopf estimates. αγ angular correlation measurements of the transitions 269.6 keV, 324.1 keV, and 338.6 keV and an αγ linear polarization measurement of the 269.6 keV transition were performed for spin determination. We assign $\text{I =}\text{7}\text{2}$ to the ²¹⁹Rn ground state and $\text{I =}\text{5}\text{2}$ or $\text{9}\text{2}$ to the 269.6 keV state. All other low excitations including the 338.6 keV level have spins $\text{I =}\text{5}\text{2}$, $\text{7}\text{2}$, or $\text{9}\text{2}$. The spins of the states 158.7 keV and 14.4 keV are equal. The ²²³Ra ground state spin is $\text{I =}\text{7}\text{2}$ or $\text{9}\text{2}$. The possibility of an interpretation of the transitional nucleus ²¹⁹Rn in the frame of the collective model is discussed.     

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.     

Magnetic rotation of levels of 53Mn and 54Mn following the 53, 54Cr(p,n) and 51V(α, n) reactions

The low-lying levels of ⁵³Mn and ⁵⁴Mn have been studied using the ^{53, 54}Cr(p, nγ) and ⁵¹V(α, nγ) reactions. Angular distributions of γ-rays have been measured and their integral rotations in iron alloy targets studied. The g-factor of the 377 keV, $\text{5}\text{2}{}^{\mathrm{?}}$ level of ⁵³Mn is g = + 1.15±0.17. Products gτ have been found for the 55, 156, 368, 408 and 1072 keV levels of ⁵⁴Mn to be 124±42, 360±60, 75±25, > 10 and 150±80 ps respectively. Using shell model estimates for the g-factors, the lifetimes of the levels have been deduced. An interpretation of the results in terms of shell model wave functions is given.     

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 $\text{7}\text{2}{}^{\mathrm{?}}$.     

Gamma transitions in 59Ni following the β+ decay of 59Cu

The γ-ray decay spectrum of 82 s ⁵⁹Cu produced by the ⁵⁸Ni(p, γ) ⁵⁹Cu reaction has been studied with a 40 cm³ Ge(Li) detector. The number of γ-rays now known for this decay has more than doubled. Additional direct β⁺ branches to the 1679.7($\text{5}\text{2}{}^{\mathrm{?}}$), 2414.8($\text{3}\text{2}{}^{\mathrm{?}}$) and 2681 keV states of ⁵⁹Ni have been identified with log ft values of 5.5, 5.5 and 6.0, respectively. A major change is the reassignment of the 1340.4 keV γ-ray to a 1679.7 → 339.3 keV transition. A limit of log $\text{ft ≧ 6.9}$ is given for the direct feeding of the 1337($\text{7}\text{2}{}^{\mathrm{?}}$) keV state, together with limits for direct population of other energetically available states. The new weak γ-ray branches found for the 878.0, 1301.5 and 1679.7 keV levels are in excellent agreement with the recent theoretical calculations of Glaudemans et al.     

Nuclear matrix elements in the first-forbidden β-decay of 125Sb

Nuclear matrix elements in the $\text{7}\text{2}$⁺(444 keV β^?)$\text{9}\text{2}$^?(177 keV γ)$\text{11}\text{2}$^? β-γ cascade in have been extracted from the available experimental data. A significant cancellation in the Coulomb-enhanced matrix element combination permits good limits of error to be placed on the individual matrix elements, even though there is not a large amount of experimental data available.     

The β-decay of 47V

The γ-rays emitted following the β-decay of ⁴⁷V have been studied with a 65 cm³ Ge(Li) detector. Direct β-branches were observed to the following levels in ⁴⁷Ti (log ft values in parentheses): ground state (4.9); 1550 keV (6.0); 1794 keV (5.1); 2163 keV (5.3); 2167 keV (6.2); 2526 keV (5.4); 2549 keV (5.7); 2793 keV (5.0). The branches to the last four levels have not been reported previously. In addition, a newγ-decay branch, 2163 → 160 keV, was observed. These results, together with information from reaction studies, permit the assignment of spin and parity $\text{3}\text{2}{}^{\mathrm{?}}$ to the 2163 keV level, and $\text{5}\text{2}{}^{\mathrm{?}}$ to the 2167 keV level. The half-life of the ⁴⁷V decay was measured to be 32.6±0.3 min.     

The magnetic dipole moment of 55Co

The ground state g-factor for ⁵⁵Co has been measured as $\text{¦g¦= 1.378±0.001}$ by the technique of nuclear magnetic resonance on oriented nuclei. The temperature dependence of γ-ray anisotropy in the ⁵⁵Fe daughter decay determines both the 1408 keV level spin and the ⁵⁵Co ground state spin to be $\text{7}\text{2}$, and yields values of mixing ratios in the 1037 keV β-transition and the 477 keV γ-transition. The configuration mixing model is used to discuss 1f_{$\text{7}\text{2}$} moment systematics.     

Spins of the levels and multipole mixing ratios of transitions in 125Sb determined from γ-γ directional correlation and polarization-directional correlation measurements

In order to resolve several discrepancies in spin assignments to levels in ¹²⁵Sb, directional correlations and polarization-directional correlations have been measured for several γ-γ cascades in ¹²⁵Sb populated from the decay of ¹²⁵Sn. Earlier results obtained from using NaI and Ge(Li) and NaI detectors were difficult to interpret due to the complex structure of the decay scheme. To improve the experimental situation, we have used two coaxial Ge(Li) detectors for the angular correlation measurements and a coaxial Ge(Li)-planar Ge(Li) combination for the polarization-directional correlations. Combination of the results of these measurements give unique spin assignments of $\text{11}\text{2}$^?, $\text{11}\text{2}$^?, $\text{9}\text{2}$⁺, $\text{11}\text{2}$⁺ and $\text{9}\text{2}$⁺ to the 1982 keV, 1890 keV, 1420 keV, 1089 keV and 1067 keV levels, respectively. The determined E2/M1 mixing ratios are : δ(470) = 0.010±0.027, δ(1067) = ?0.86±0.18, and δ(916) = ?0.02±0.01.     

Isomers in the N = 83 nucleus 149Dy

Energy levels in the N = 83 nucleus ¹⁴⁹Dy were studied by the reaction ¹⁵²Gd(α, 7n) at 106 MeV bombarding energy using in-beam γ-ray spectroscopy methods. The measurements identified three isomers in this nucleus, at 1073 keV (13 ± 3 ns), at 2700±150keV (5 μs < T_{$\text{1}\text{2}$} < 0.5 s), and above 3.5 MeV (50 ± 15 ns). The low-lying isomer is interpreted as i_{$\text{13}\text{2}$}. The configuration $\text{27}\text{2}$^?(πh_{$\text{11}\text{2}$}²)₁₀₊ ×vf_{$\text{7}\text{2}$} is suggested for the state at 2.7 MeV.     

Alpha-decay of 39.3 h 254mEs isomer

Mass-separated samples of ^254mEs were used to investigate its α-decay scheme. Twelve α-groups were identified in a spectrum measured with the Argonne magnetic α-spectrometer. The favored α-transition populates a 211.8 keV level in ²⁵⁰Bk and four members of its rotational band were observed. A three-parameter α-γ time coincidence experiment showed that the 211.8 keV level decayed by three routes: two were prompt and one was delayed. The delayed γ-rays (50.07, 71.30, 90.7, 104.0, 126.0 and 175.7 keV) decayed with a 42±2ns half-life. The energies of the prompt γ-rays were 79.90, 96.3, 177.3 and 211.8 keV. From an α-ce^? coincidence experiment the multipolarity of the 211.8 keV transition was deduced to be E1. The α-branching was determined from an α-singles spectrum and was found to be 0.33±0.01%. From the results of the present investigation and the known properties of ²⁵⁰Bk and ^254mEs, the 211.8 keV state in ²⁵⁰Bk and the ^254mEs ground state were given $\text{{}\text{n}\text{[622]}\text{3}\text{2}{}^{\mathrm{+}}\text{;}\text{p}\text{[633]}\text{7}\text{2}{}^{\mathrm{+}}\text{2}{}^{\mathrm{+}}$ assignment. Other levels in ²⁵⁰Bk were postulated at 104.0 (and its rotational member at 125.3), 131.9 and 175.3 keV and these were given tentative assignments of $\text{n}\text{[620]}\text{1}\text{2}{}^{\mathrm{+}}\text{;}\text{p}\text{[521]}\text{3}\text{2}{}^{\mathrm{?}}\text{1}{}^{\mathrm{?}}\text{,}\text{n}\text{[620]}\text{1}\text{2}{}^{\mathrm{+}}\text{;}\text{p}\text{[633]}\text{7}\text{2}{}^{\mathrm{+}}\text{3}{}^{\mathrm{+}}$ and $\text{n}\text{[613]}\text{7}\text{2}{}^{\mathrm{+}}\text{;}\text{p}\text{[633]}\text{7}\text{2}\text{O}{}^{\mathrm{+}}$ (with I = 1), respectively. The splitting energies between the parallel and antiparallel coupled states were calculated with a Gaussian potential for the residual neutron-proton interaction and were found to be in agreement with the experimental values. A precise measurement of the energies and intensities of γ-rays and K X-rays associated with the ^254mEs β^? decay was also made. The Fm K_α2 and K_α1 energies were found to be 115.280±0.015 and 121.065±0.015 keV, respectively.     

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.     

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.