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.     

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 $\text{E}{}_{\mathrm{\gamma }}{}^1\text{> 50}\text{MeV}$.     

Investigation of high-spin states in 47Ca through double-step processes in the 48Ca(τ, α)47Ca reaction

In the ⁴⁸Ca (τ,α)⁴⁷Ca reaction at 25 MeV, some angular distributions are well reproduced by CCBA calculations, assumping double-step excitation of $\text{[}{}^{48}\text{Ca}{}^1\text{?}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{]}$ states. Unambigous J^π assignments are extracted from the analysis.     

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.     

The 2425 keV state in 21Na as a subtreshold resonance in 20Ne (p,γ)21 Na

The high-energy tail of the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$, 2425 keV state in ²¹Na, bound by 7 keV against proton decay, has been observed in the ²⁰Ne (p,γ)²¹Na reaction at E_p=0.5?1.5 MeV. The observed excitation function is consistent with a single-level Breit-Wigner shape with Γ_γ=0.31±0.07 eV at E_x = 2425 keV.     

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.     

Competition cusps in (α, γ) reactions

Absolute cross sections are presented for the reactions ³⁷Cl(α, γ)⁴¹K for 2.90 MeV ≦ E^lab_α ≦ 5.23 MeV, ${}^{62}\text{Ni}\text{(α, γ)}{}^{66}\text{Zn}\text{for}\text{5.07}\text{MeV}\text{≦ E}{}_{\mathrm{\alpha }}{}^{\mathrm{?2}}\text{lab}\text{≦ 8.64}\text{MeV}\text{,}{}^{62}\text{Ni}\text{(α,}\text{n}\text{)}{}^{65}\text{Zn}$ for energies near the (α, n₀) threshold at $\text{E}{}_{\mathrm{\alpha }}{}^{\mathrm{<mtext>lab</mtext>}}\text{= 6.90}\text{MeV up to}\text{8.76}\text{MeV}\text{,}{}^{64}\text{Ni}\text{(α, γ)}{}^{68}\text{Zn for}\text{4.50 ≦ E}{}_{\mathrm{\alpha }}{}^{\mathrm{<mtext>lab</mtext>}}\text{≦ 7.45}\text{MeV}$, and for ⁶⁴Ni(α, n)⁶⁷N from E_α^lab = 5.30 MeV up to E_α = 7.45 MeV. Substantial competition cusps were observed in the excitation function for all three (α, γ) reactions. The data were found to be in reasonable agreement with the predictions of the current versions of global Hauser-Feshbach models used in nucleosynthesis calculations. Including width fluctuation corrections and realistic neutron strength functions generally improves the ability of the models to predict the depth of the (α, γ) competition cusps; the depths of the predicted (α,γ) cusps are insensitive to the degree of isospin mixing. Taken together with studies of competition effects in proton-induced reactions, the present data confirm the importance of width fluctuation and strength function effects, and indicate essentially complete isospin mixing between T^< and T^> states in the compound nucleus.     

Resonances in the reaction 56Fe(p, γ)57Co

Resonances in the reaction ⁵⁶Fe(p, γ)⁵⁷Co have been surveyed over the energy range 1.2 ? E_p ? 1.5 MeV wherein the analogues of the ground state $\text{(J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{?}}\text{, 0.014}\text{MeV}$ state $\text{(J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$ and 0.136 MeV state $\text{(J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{?}}\text{)}$ of ⁵⁷Fe are expected to occur. Gamma-ray angular distributions have been used to establish resonance and bound-state spins, and decay schemes have been determined. The analogue resonances appear to be severely fragmented, however the density of resonances of a given spin correlates quite well with (³He, d) results and with the expected analogue-state positions.     

Das Niveauschema von 47V aus dem γ-zerfall von Analogresonanzen

A high-accuracy investigation of the level scheme of ⁴⁷V has been performed using the ⁴⁶Ti(p, γ)⁴⁷V reaction. The γ-decay schemes of the strong (p, γ) resonances at E_p = 1546, 1549, 1565 and 1572 keV lead to 17 new energy levels in ⁴⁷V with excitation energies between 2.7 and 5.1 MeV. From the (p,γ) angular distributions mixing ratios of the primary γ-transitions and J^π values of the resonances and of many states populated in the γ-decay have been determined. The total width of the E_p = 1549, 1565 and 1572 keV resonances for γ-decay are found to be Γ_γ = 0.12, 0.15 and 0.03 eV, respectively. The Q-value of the ⁴⁶Ti(p,γ)⁴⁷V reaction is found to be 5168.6 keV. The two resonances at E_p = 1549 and 1565 keV, which have $\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}$, are interpreted as fine structure components of the analogue state of the $\text{E}{}^1\text{= 2.545}\text{MeV}\text{J}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{?}}$ level in ⁴⁷Ti while the ($\text{7}\text{2}$) resonance at E_p = 1546 keV might correspond to the $\text{E}{}^1\text{= 2.615}\text{MeV}\text{7}\text{2}{}^{\mathrm{?}}$ parent state in ⁴⁷Ti. The analogue-antianalogue M1 transition strength of the split $\text{3}\text{2}{}^{\mathrm{?}}$ analogue state is 0.01 single-particle units and fits well into our systematics of IAS → AIAS transitions in fp-shell nuclei.     

A comment on the phenomenology of the SU(3) Skymre model

We find that the realistic baryon mass spectrum in the SU(3) Skyrme model with massive 0^? mesons can be obtained only for F_π < 70 MeV. We fit m_Λ and and obtain baryon masses within the limits of ± 16% of the experimental val ues, but at the expense of very low ifF_π=46.32 MeV.     

Evidence for two narrow pp resonances at 2020 MeV and 2200 MeV

From the study of the reaction $\text{π}{}^{\mathrm{?}}\text{p→p}{}_{\mathrm{F}}\text{p}\text{p}\text{π}{}^{\mathrm{?}}$ using a fast proton (p_F) trigger device in the CERN Omega spectrometer, we find evidence for two narrow $\text{p}\text{p}$ states produced mainly in association with a Δ° (1232) and a N° (1520). The statistical significance of each peak is greater than 6 standard deviations. Masses and natural widths of these resonances are respectively M = 2020 ± 3 MeV, Λ₁ = 24 ± 12 MeV and M₂ = 2204 ± 5 MeV, Λ₂ = 16_?16⁺²⁰ MeV. Our data are consistent with a small production of the narrow ～ 1935 MeV resonance already reported. Production cross sections for these new $\text{p}\text{p}$ resonances are given.     

Spin determination of states with stretched configurations in 16N and 32P via the (d, α) reaction at 52 MeV

The reactions ${}^{12}\text{C}\text{(}\text{d}\text{, α)}{}^{10}\text{B}\text{,}{}^{18}\text{O}\text{(}\text{d}\text{, α)}{}^{16}\text{N and}{}^{34}\text{S}\text{(}\text{d}\text{, α)}{}^{32}\text{P}$ have been investigated at E_d = 52 MeV. Vector analyzing powers as large as $\text{¦iT}{}_{11}\text{¦=0.85}$ are observed. They exhibit patterns characteristic for final spins I = |L?1|, L or L + 1 and provide spin determinations at least for states of unique L-transfer. Local, zero-range DWBA calculations assuming deuteron-cluster pick-up reproduce qualitatively the observed effects. The method has been tested for states of known spin, and then has been applied to determine spins of states with stretched coupling in ¹⁶N: J^π = 3⁺(3.96 MeV), 4^?(6.17 MeV) and in ³²P: J^π = 5⁺(4.75 MeV). There is strong evidence for further 5⁺ states in ³²P at 6.43, 7.96, 8.09 and 8.54 MeV.     

Generalization of multiperipheral model with long range correlations; Van Der Waals approximation

Three enhancements are observed in the final state ω^°π⁺π⁺π⁺⁺π^?π^? selected from the channel $\text{p}\text{p → 3π}{}^{\mathrm{+}}\text{3π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{°}}$ at 715 MeV/c: one in ω^°π^± at 1040 MeV (～ ≈ 55MeV) ω^°π⁺π^?, respectively near 1315 MeV (～ ≈ 100 MeV) and 1405 MeV (～ ≈ 40 MeV). The first two effects are strongly correlated and are interpreted in terms of a sequential decay A^°₂ through a new object, the B₁. The second (ωππ) enhancement seems to be an ?^°?^° effect below threshold and is attributed to a pionic decay of the $\text{K}\text{K}\text{)}{}_{\mathrm{I}}\text{=1}$ effect seen around the same mass in other reactions.     

Ground-state properties of 3h 184Ir and 14h 185Ir

The ground-state spectroscopic quadrupole moments of ${}^{184}\text{Ir [J}{}^{\mathrm{\pi }}\text{=(5}{}^{\mathrm{\pm }}\text{);t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{=3.00]}$ and ${}^{185}\text{Ir (J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{?}}\text{;t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 14}\text{h}\text{)}$ have been determined by nuclear orientation as +2.2(4) b and ?2.03(3) b, respectively. The negative QM of ¹⁸⁵Ir can be explained only by a $\text{J}{}^{\mathrm{\pi }}\text{K=}\text{5}\text{2}{}^{\mathrm{?}}\text{1}\text{2}$ ground-state configuration. The positive QM of ¹⁸⁴Ir implies K ? 4 in contradiction to expectations of K=0, 1 in analogy to ¹⁸⁶Ir.     

Spectroscopy of states in 33S by means of neutron-gamma angular correlation measurements

Levels of ³³S for E_x < 5 MeV have been studied with the ³⁰Si(α, nγ)³³S reaction at bombarding energies of E_α = 7.5 and 10.2 MeV. Neutron-gamma angular correlation experiments lead to three unambiguous spin and parity assignments: $\text{J}{}^{\mathrm{\pi }}\text{(3.83) =}\text{5}\text{2}{}^{\mathrm{+}}\text{, J}{}^{\mathrm{\pi }}\text{(4.048) =}\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{J}{}^{\mathrm{\pi }}\text{(4.09) =}\text{7}\text{2}{}^{\mathrm{+}}$. The measured branching and mixing ratios yield transition strengths for dipole and quadrupole transitions.     

15N(p,po)15N and the levels of 16O for Ex = 14.8–18.6 MeV

Angular distributions of cross section and analyzing power for elastic scattering of protons from ¹⁵N have been measured for E_p = 2.7–7.0 MeV. A phase-shift analysis of the data yields spin-parity assignments and level parameters for seventeen states of ¹⁶O in the excitation energy region 14.8–18.6MeV. Three of the resonances have not previously been identified, among them being a broad J^π = 2^? level at E_p = 6.1 MeV which is almost certainly the analog of the 2^? 1p1h state with configuration ($\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{,}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$) at E_x ∽ 5.0 MeV in ¹⁶N. The broad level previously reported near E_p = 5.0 MeV has been observed and its parameters determined. A resonance analysis of the phase shifts yielded values of E_r, Γ and Γ_p for all of the levels. The J^π assignments are in agreement with previously reported values. For resonances having J = l, the data can usually be fit with a resonant phase shift corresponding to either J = l + 1 or J = l ? 1, in addition to the phase shift for J = l. Which of the two spurious-J solutions occurs seems to depend on whether the partial wave through which the resonant state is formed is $\text{J = l +}\text{1}\text{2}\text{or}\text{J = l ?}\text{1}\text{2}$.     

Measurement of charge distributions for 229Th(nth,f) and 232U(nth,f)

A gas ΔE ? E_R telescope has been used to measure charge yields and their correlations with kinetic energies for ²²⁹Th and ²³²U. Even-charge yields are enhanced compared with odd-charge yields for both fissioning systems; this enhancement increases for events with higher kinetic energy. The mean odd-even effect $\text{δ}{}_{\mathrm{<mtext>p</mtext>}}\text{is}\text{= (40±4)\%}\text{for}{}^{229}\text{Th}$; it is $\text{(21 ± 3)\%}\text{for}{}^{232}\text{U-the same as for}{}^{233}\text{U}\text{((22.1±2.1)\%)}\text{and}{}^{235}\text{U}\text{((23.7±0.7)\%)}$. The energy-integrated δ_p and δ_p for different energy windows, vary strongly as a function of charge (Z) due to the underlying shells. The δ_p averaged over Z increases fast with kinetic energy, contrary to the existing results for ²³³U and ²³⁵U, where δ_p flattens off at low energies. For both systems, the most probable kinetic energy ē shows a strong odd-even stagger; the mean odd-even effect on energy, $\text{δE}{}_{\mathrm{<mtext>K</mtext>}}{}^{\mathrm{<mtext>o?e</mtext>}}\text{,}\text{is}\text{1.4 ± 0.3}\text{MeV for}{}^{229}\text{Th, and}\text{1.7±0.4}\text{MeV for}{}^{232}\text{U}\text{—}$ the latter is about twice the value for ${}^{233}\text{U}\text{(0.95 ± 0.09}\text{MeV}\text{)}\text{and}{}^{235}\text{U}\text{(0.7}\text{MeV}\text{)}$. These results are discussed in terms of the existing models.     

Study of isovector charge-exchange excitations and their decay via the 16O(3He,tp) reaction

The nucleus ¹⁶F was studied via the ¹⁶O(³He, t) reaction at 81 MeV. Differential cross sections for many states were obtained and interpreted with DWBA calculations, using microscopic wave functions and an effective projectile-nucleon interaction. Proton decay to several states in ¹⁵O was observed and angular correlations for protons in coincidence with tritons detected at θ = 0° were measured. Several spin-parity assignments have been made. The distribution of isovector ΔL = 1 strength could be deduced. The analog of the giant dipole resonance ($\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{? 9.5}\text{MeV}\text{)}$ is strongly excited. The magnetic quadrupole strength has two strong components, one low, at E_x = 0.424 MeV, and one high, at $\text{E}{}_{\mathrm{<mtext>x</mtext>}}\text{? 7.5}\text{MeV}$. Evidence is given for a proportionality between cross section and M2 strength for transitions to J^π = 2^? states, which possibly make the (³He, t) reaction a suitable tool for determining quantitatively isovector M2 (or B_ij) strengths.