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.     

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.     

Lifetimes of the low-lying 72− states in 113, 115Cd

The half-lives of the $\text{7}\text{2}{}^{\mathrm{?}}$ states at 522.6 and 393.9 keV in ¹¹³Cd and ¹¹⁵Cd have been determined to be 0.322±0.012 and 0.75± 0.03 ns, respectively. Values of the $\text{B(}\text{E}\text{2,}\text{7}\text{2}{}^{\mathrm{?}}\text{→}\text{11}\text{2}{}^{\mathrm{?}}$) and the energy difference in odd Cd (A = 113–119) are compared with those in neighbouring even Cd. The level properties are interpreted in the framework of the triaxial rotor model.     

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.     

Magnetic moments at backbending and spectroscopy of 134Ce

Employing the static hyperfine fields at cerium nuclei in magnetized Fe and Gd hosts, the g-factor of the ¹³⁴Ce(10⁺) state at backbending (E_{x = 3719.3 keV}) has been determined as g = ? 0.30 (25). The coexistence of this neutron-dominated state with the ($\text{v}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{n}}\text{10}{}^{\mathrm{+}}$ isomer (E_x = 3208.5 keV, g = ?0.19(1)) is unexpected. A comprehensive spectroscopic study following the ¹²²Sn(¹⁶O, 4n) reaction, including γ-angular distributions, prompt and delayed γ coincidence and recoil-distance measurements has yielded new information on quasi-collective bands of both parities. The properties of the low-lying positive-parity states are well described by the interacting boson model.     

Study of the photon spectrum in the decay KS0→π+π−γ

The branching ratio $\text{Λ(}\text{K}{}_{\mathrm{<mtext>S</mtext>}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{γ)}\text{Λ(}\text{K}{}_{\mathrm{<mtext>S</mtext>}}{}^0\text{→π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ has been determined to be (2.68±0.15)×10^?3 for photon energies $\text{E}{}_{\mathrm{\gamma }}{}^1$ greater than 50 MeV in the K_S⁰ rest frame. The decay K_S⁰→π⁺π^?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10^?3 at 90% confidence level for $\text{E}{}_{\mathrm{\gamma }}{}^1\text{> 50}\text{MeV}$.     

Polarization spectroscopy of the E0g+-B0u+ band system of Br2

The E-B (0_g⁺-0_u⁺) band system of Br₂ has been investigated at Doppler-limited resolution using polarization labeling spectroscopy. Merged E state data for the three naturally occurring isotopes in the range v_E = 0–16, expressed in terms of the constants for ⁷⁹Br₂, are (in cm^?1) Y_0,0 = 49 777.962(54), Y_1,0 = 150.834(22), Y_2,0 = ?0.4182(28), Y_3,0 = 6.6(11) × 10^?4, Y_0,1 = 4.1876(28) × 10^?2, Y_1,1 = ?1.607(16) × 10^?4, and Y_0,2 = 1.39(39) × 10^?8. The bond distance is $\text{r}{}_{\mathrm{<mtext>e</mtext>}}\text{= 3.194}\text{A}\text{?}$, and the diabatic dissociation energy to $\text{Br}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_2\text{) +}\text{Br}{}^{\mathrm{?}}\text{(}{}^1\text{S}{}_0\text{)}\text{is 34 700 cm}{}^{\mathrm{?1}}$.     

The 5T2g → 5Eg absorption in MgO: Fe2+

At helium temperatures two sharp lines at 9350 and 9510 cm^?1 have been observed for the first tune on the low-energy side of the broad double-peaked absorption corresponding to the ${}^5\text{T}{}_{\mathrm{2g}}\text{→}{}^5\text{E}{}_{\mathrm{g}}$ transition in Fe²⁺ at the octahedral site in MgO. The lower energy line has a half width of 4 cm^?1; Zeeman measurements show that it is of magnetic dipole origin. The Zeeman spectra are consistent with those expected for a pure electronic transition from the (⁵T_2g)T_2g ground state to the ⁵E_g excited state. The second line, with a halfwidth of ~ 35 cm^?1, a vibrational sideband.     

The γ-decay of the g92 analogue state in 59Cu

An investigation of the γ-decay of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ analogue state in ⁵⁹Cu has been performed using the ⁵⁸Ni(p, γ)⁵⁹Cu reaction. The (p, γ) excitation function has been taken in the range E_p = 3450–3650 keV. The decay schemes of the (p, γ) resonances at E_p = 3483, 3532 and 3547 keV, measured with Ge(Li) detectors, lead to eight new levels in ⁵⁹Cu with excitation energies between 1.8 and 4.7 MeV and to spin assignments of several states. The spins of the first two resonances are found to be ($\text{1}\text{2}$, $\text{3}\text{2}$) and ($\text{5}\text{2}$). The spin of the E_p = 3547 keV resonan is, from angular distributions, uniquely determined to be $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ and this state is found to be the unfragmented analogue state of the $\text{E}{}^1\text{= 3.062}\text{MeV}$, $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{+}}$ parent state in ⁵⁹Ni. The measured complete decay scheme of this resonance shows that its isovector M1 decay is in disagreement with all existing theoretical predictions.     

Model calculation of the electronic structure and spectroscopy of Hg2

Energy curves and transition moments of the excited valence states of Hg₂ were obtained in a model calculation based on calculated Mg₂ energy levels and the assumption that the asymptotic spin-orbit matrix elements for the Hg atom are applicable to the molecular states. The spin-orbit and orbital-rotational interaction of the excited states of Hg₂ is analyzed in both a Hund's case (c) and (a) representation. The intermediate (a) → (c) transition moments are obtained as a function of the internuclear distance. The effect of the orbital-rotational interaction which introduces Hund's case (b) and (e) couplings is found to be small for transitions among excited states under the conditions normally encountered for populating excimer states.Using the energy level positions and transition moments, the observed spectra and predicted spectra are compared for both radiative transitions including the ground state and among the excited states. The lifetime of the $\text{1}{}_{\mathrm{u}}\text{(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ excimer state is calculated to be 1.4 μsec with the 335 nm band assigned to the $\text{1}{}_{\mathrm{u}}\text{→ X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transition. The 485 nm bands cannot be assigned to any Hg₂ transitions. Strong bound-continuum absorptions are predicted for the 485 nm bands. On the other hand, the 335 nm emission is predicted to be absorbed by bound-bound transitions only.     

Radiative decay of lithium-like ions following charge exchange collisions of 60 keV O6+ ions with H2

The distribution of captured electrons in the 60 keV $\text{O}{}^{\mathrm{6+}}\text{+}\text{H}{}_2\text{→}\text{O}{}^{\mathrm{5+1}}\text{(nl) +}\text{H}{}_2{}^{\mathrm{+}}$ collision is studied by detection of the subsequent far UV radiation. Strong lines corresponding to the 4f → 3d → 2p cascade have been observed. Assuming that capture to the n = 4 manifold dominates at this energy, a relative population of the l sublevels which increases with l-value is obtained.     

High-spin states in 38K

High-spin states in ³⁸K are investigated with the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction at $\text{E(}{}^{16}\text{O}\text{) = 36–44}\text{MeV}$. A recently developed Compton-suppression spectrometer with 120 msr solid angle and a pulsed beam are employed to study their γ-decay. For the E4 transition from the isomeric level at E_x = 3458 keV to the ground state a branching ratio of (0.15 ± 0.02)% is found. On the basis of angular distribution and polarization measurements, in which the delayed feeding component is eliminated, spin-parity assignments are obtained of J^π(2646 keV) = (2, 4)^?, J^π(3420 keV) = (4, 6)^? and J^π(3458 keV) = (5, 7)⁺. Prompt-delayed and prompt γγ coincidence experiments are performed to locate high-spin levels above the isomer. Hitherto unobserved levels of high spin are found at E_x = 5254, 7397, 8693, 8747 and 10980 keV and assignments of J^π = (9⁺), (10^?), (12^?), (11^?) and (13^?) respectively, are suggested by weak-coupling considerations. The experimental results are compared with a large-scale shell-model calculation performed in a configuration space with a ²⁸Si core and ten active particles distributed over the ($\text{2}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, 1}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 1}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{, 2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}$ shells. The high-spin states appear to have a rather simple shell-model structure.     

Measurement of the 2S12−2P12 splitting in the (μ−4He)+ muonic ion

The measurement of the $\text{2S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{→ 2P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ energy transition in muonic helium is presented. The energy difference S¹ is found to be S_exp¹ = 1381.3±0.5 meV. This result agrees with the expected value $\text{S}\text{?}{}^1\text{= 1381.2±0.3}\text{meV}$ obtained assuming the previously measured value for the $\text{2S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{→ 2P}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ energy difference.     

Absolute E1, ΔK = 1 transition probabilities between multi-quasiparticle high-spin states in 176Hf and 178Hf

Applying the generalized centroid shift method in (α, 2n) reactions, the half-lives of the 3080 keV 15⁺ state in ¹⁷⁶Hf and of the 1637 keV 5^? state in ¹⁷⁸Hf have been measured as $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.20}{}^{\mathrm{+0.12}}{}_{\mathrm{?0.08}}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.40 ± 0.10}\text{ns}$, respectively. B(El) values of K-allowed E1 transitions $\text{n}\text{9}\text{2}{}^{\mathrm{+}}\text{[624]→}\text{7}\text{2}{}^{\mathrm{?}}\text{[514]}$ are derived, and together with other data on similar transitions in odd-A nuclei, compared with predictions of the Nilsson plus pairing model. In ¹⁷⁶Hf, the 15⁺ and 14^? states at 3080 and 2866 keV, respectively, appear as quite pure deformed 4QP configurations. In the 2QP state at 1637 keV in ¹⁷⁸Hf, possible strong mixing of vibrational components is discussed coupled via 2QP K-admixtures arising from the partial alignment of the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutron.     

Angular distributions of the 2h(d, γ)4he reaction

Angular distributions of γ-rays from the ²H(d, γ)⁴He reaction have been measured at the deuteron energies E_d = 6.05, 8.96 and 11.67 MeV with a 12.7 cm × 15.2 cm NaI(Tl) crystal enclosed in a Cerenkov anticoincidence shield. A least-square fit of the angular distributions indicates that the differential cross section is proportional to sin²θ cos²θ and that the process proceeds through an E2 transition of the type ${}^1\text{D}{}_2\text{→}{}^1\text{S}{}_0$.     

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.     

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.     

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^?.     

Spectrum and structure of the He2 molecule: Characterization of the triplet states associated with (1σg)2(1σu)nsσ, ndσ, ndπ, and ndδ (n = 5–12)

Emission spectra for the electronic transitions $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 2pπ b}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 5–12)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 2pπ b}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 5–12)}$, $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 3pσ c}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 5–10)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 3pσ c}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 5–11)}$, $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}\text{) → 3pπ e}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 6–11)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 3pπ e}{}^3\text{Π}{}_{\mathrm{g}}\text{(n = 6–11)}$, $\text{nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{→ 4pσ g}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{(n = 9–11)}$, and $\text{10dδ}{}^3\text{Δ}{}_{\mathrm{u}}\text{→ 4pσ g}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ of ⁴He₂ are reported and the electronic structure of the triplet states associated with v = 0 of (1σ_g)²(1σ_u) nsσ and ndλ characterized. The energy levels comprising the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ and the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)ndλ(}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{)}$ manifolds exhibit strong channel mixing, while the mixing of the $\text{(1σ}{}_{\mathrm{<mtext>g</mtext>}}\text{)}{}^2\text{(1σ}{}_{\mathrm{<mtext>u</mtext>}}\text{)nsσ}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ with the $\text{nd(}{}^3\text{λ}\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ channel structure is relatively minor. Models based on multichannel quantum defect theory are used to aid in the spectral assignments and to correlate the observed level structures. We show that three-limit and two-limit models adequately represent the bulk of the observed $\text{ndλ(}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{+}}\text{)}$ and $\text{ndλ(}{}^3\text{Π}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{,}{}^3\text{Δ}{}_{\mathrm{u}}{}^{\mathrm{?}}\text{)}$ channel structures, respectively.     

The (g92)2 residual interaction from 87Sr(d,t)86Sr

Differential cross sections for ⁸⁷Sr(d, t)⁸⁶Sr transitions to the $\text{(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ states of ⁸⁶Sr were obtained with the Pittsburgh 18 MeV deuteron beam and the Enge split-pole spectrograph. States of ⁸⁶Sr up to 3.82 MeV in excitation were studied with a total resolution of 12 keV. Successful distorted-wave Born approximation (DWBA) predictions for ⁸⁷Sr(d, t) ⁸⁶Sr angular distributions permitted the extraction of l-values and spectroscopic strengths. The sum-rule value agrees with the observed value for the $\text{(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ configuration. The observed $\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ strength is spread over 13 states. Contrary to an earlier interpretation, the 0⁺ ground state is found to contain only 65% of the strength. Similarly, the full 4⁺ strength is not located in a single state. The new data change the interpretation of the $\text{(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}$ spectrum of ⁸⁶Sr. They significantly alter the deduced low-spin matrix elements and bring them into much closer agreement with those derived from ⁸⁸Y. Several new negative-parity states dominated by l = 1 orbital angular momentum transfer have also been identified.