A useful spectroscopic tool: The (7Li, 6He) reaction

Angular distribution measurements for the reactions ²⁴Mg(⁷Li, ⁶He)²⁵ Al and ⁵²Cr(⁷Li, ⁶He)⁵³ Mn at$\text{E(}{}^7\text{Li) = 34}$ MeV show that for angles less than 15°, the shapes of the measured angular distributions allow $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ or $\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$, and $\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ or $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ final-state configurations to be distinguished when compared with finite-range DWBA calculations.     

Nucleon-exchange type charge-exchange process and the spin-forbidden (6Li, 6He) transitions

The second order DWBA formalism for the nucleon pick-up and stripping type two-step process is presented for the cases of exact finite-range interaction, no-recoil approximation and zero-range approximation. The several first-order “spin-forbidden” charge-exchange (⁶Li, ⁶He) transitions are investigated by such direct nucleon-exchange mechanisms. They are the analog transitions: ${}^{26}\text{Mg}\text{(0}{}^{\mathrm{+}}\text{) →}{}^{26}\text{Al}\text{(0.226}\text{MeV}\text{0}{}^{\mathrm{+}}\text{)}$ and ${}^{42}\text{Ca}\text{(0}{}^{\mathrm{+}}\text{→}{}^{42}\text{Sc}\text{(}\text{g.s.}\text{0}{}^{\mathrm{+}}\text{)}$, and the natural parity state excitations: ${}^{48}\text{Ca}\text{(0}{}^{\mathrm{+}}\text{) →}{}^{48}\text{Sc(g.s.}\text{6}{}^{\mathrm{+}}$ and 0.253 MeV 4⁺). The spin-flip mechanisms using a spin-independent force through the direct nucleon-exchange process are discussed. This type of two-step approach can provide a satisfactory interpretation for these transitions. It may also indicate a strong nucleon-exchange type charge-exchange mechanism for allowed transitions.     

High-spin states in 40K investigated with the 26MG + 16O reaction

Yrast levels in ⁴⁰K and ⁴⁰Ar have been investigated with the ²⁶Mg(¹⁶O, pnγ)⁴⁰K and ²⁶Mg(¹⁶O, 2pγ)⁴⁰Ar reactions at a beam energy of 34 MeV. Gamma-ray angular distribution and γ-γ coincidence measurements have been performed with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. Gamma-ray linear polarizations have been measured with a three-crystal Ge(Li) Compton polarimeter. The ⁴⁰K decay scheme involves new high-spin levels at E_tx = 4365.6±0.3, 4875.6±0.4 and 6227.0±0.5 keV with lifetime limits of < 1, < 1 and < 2ps, respectively. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{= 5}{}^{\mathrm{?}}\text{, 6}{}^{\mathrm{+}}\text{, 8}{}^{\mathrm{+}}\text{, 9}{}^{\mathrm{+}}\text{and}\text{(8, 10)}{}^{\mathrm{?}}$ to the ⁴⁰K levels at E_x = 0.89, 2.88, 4.37, 4.88 and 6.23 and of $\text{J}{}^{\mathrm{\pi }}\text{= 4}{}^{\mathrm{+}}\text{and}\text{6}{}^{\mathrm{+}}\text{to the}{}^{40}\text{Ar}$ levels at E_x = 2.89 and 3.46 MeV, respectively, have been obtained. Branching ratios and multipole mixing ratios are reported.     

Spin-parity assignments to high-spin states of 41K and 41Ca

Yrast states of ⁴¹K and ⁴¹Ca have been investigated with the ²⁶Mg(¹⁸O, p2nγ)⁴¹K and ²⁶Mg(¹⁸O, 3nγ)⁴¹Ca reactions at a beam energy of 34 MeV. Gamma-gamma coincidence, γ-ray angular distribution and linear polarization measurements were performed with a Ge(Li)-NaI(Tl) Compton suppression spectrometer and a three-crystal Ge(Li) Compton polarimeter. Unambiguous spin-parity assignments of $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{+}}$, $\text{11}\text{2}{}^{\mathrm{?}}$, $\text{13}\text{2}{}^{\mathrm{+}}$, $\text{15}\text{2}{}^{\mathrm{?}}$ and $\text{19}\text{2}{}^{\mathrm{?}}$ to the ⁴¹K levels at E_x = 1.68, 2.53, 2.76, 2.77, 4.27 and 4.98 MeV and of $\text{9}\text{2}{}^{\mathrm{+}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{and}\text{15}\text{2}{}^{\mathrm{+}}$to the ⁴¹Ca levels at E_x = 3.20, 3.37 and 3.83 MeV, respectively, have been obtained. Excitation energies, branching ratios, multipole mixing ratios and transition strengths are reported. The main features of the ⁴¹K and ⁴¹Ca level and decay schemes are reproduced in a 2p-1h and 3p-2h shell-model calculation.     

The excited states of 27Al

The γ-decay of 60 and the strengths of 51 ²⁶Mg(p, γ)²⁷Al resonances were studied for E_p < 2.20 MeV. The energies of 32 and the γ-decay of 54 bound levels were determined. Spin and parity assignments $\text{J}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}\text{,}\text{5}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}$ were made to the bound states at E_x = 4.81, 5.44, 6.61, 6.78, 7.68 and 7.86 MeV, respectively. Spin assignments $\text{J =}\text{5}\text{2}$and $\text{3}\text{2}$ were made to the bound levels at Einx = 5.55 and 6.08 MeV, respectively. For other levels spin and parity limitations were set. Lifetimes or lifetime upper limits of 19 bound levels were measured by means of the DSA technique. The spins and/or parities of 15 resonances were unambiguously determined from γ-ray angular distributions and strengths.     

The electric quadrupole moment of the 6+ state of 112Sn

The spectroscopic quadrupole moment of the isomeric 6⁺' (2552 keV) state of ¹¹⁷Sn has been derived from TDPAD measurements in a Cd metal host target at 500 K as $\text{Q}{}_{\mathrm{<mtext>I</mtext>}}\text{(6}{}^{\mathrm{+}}\text{,}{}^{112}\text{Sn}\text{) = ± 0.29(6)}\text{b}$. The calibration of the effective field gradient for Sn in Cd at 500 K, given by Herrlander et al. has been used. A comparison of the results with shell model estimates makes a mixed configuration of $\text{|(}\text{g}\text{7}\text{2}\text{)}{}^{\mathrm{?2}}\text{6}{}^{\mathrm{+}}\text{〉)}\text{and}\text{(}\text{g}\text{7}\text{2}{}^{\mathrm{?1}}\text{d}\text{5}\text{2}{}^{\mathrm{?1}}\text{)6}{}^{\mathrm{+}}\text{〉)}$ for the 6⁺ state most likely.     

Two theorems on the level order in potential models

We study the potentials of the form U(r)=?r^?1+λV(r), $\text{(}\text{d}\text{d}\text{r}\text{)(}\text{r}{}^2\text{d}\text{V}\text{d}\text{r}\text{)?0}$, and show that the energy levels satisfy the inequalities $\text{E(N}{}_{\mathrm{c}}\text{, l)?E(N}{}_{\mathrm{c}}\text{, l+1)}$ to first order in λ, where N_c denotes the coulombic principal quantum number and l the angular momentum. Similarly for potentials $\text{U(r)=r}{}^2\text{+λV(r), (}\text{d}\text{d}\text{r}{}^2\text{)}{}^2\text{V(r)?0}$, we prove to first order in λ that $\text{E}\text{?}\text{(N}{}_{\mathrm{H}}\text{,}\text{l}\text{)?}\text{E}\text{?}\text{(N}{}_{\mathrm{H}}\text{,}\text{l}\text{+2)}$, where NH denotes the harmonic oscillator quantum number. In the latter case, we give also quantitative restrictions on the relative positions at the lth and (l+1)th states.     

The interaction of 33 MeV polarised helions with 30Si

Distributions of cross sections and analysing powers have been measured over the range ～ 14°–100° c.m. for the $\text{(}{}^3\text{H}\text{,}{}^3\text{He), (}{}^3\text{H}\text{,}{}^4\text{He), (}{}^{\mathrm{<mtext>3</mtext><mtext>H</mtext>}}\text{,}{}^2\text{H)}$ reactions at 33.4 MeV incident e using a ～ 95 % enriched ³⁰Si target. Phenomenological optical-model analyses of the elastic-scattering data have been carried out. A DWBA analysis of the inelastic-scattering data for the 2.24 MeV (2⁺) and 5.49 MeV (3^?) states of ³⁰Si has yielded values of the deformation β₂ and β₃. The j-dependence of the analysing powers for the (³He, ⁴He) and (³He, ²H) reactions has identified the 6.71 MeV level of ²⁹Si as a $\text{5}\text{2}{}^{\mathrm{+}}$ state, and a level near 9.5 MeV in ³¹P as a possible $\text{7}\text{2}{}^{\mathrm{?}}$ state. Spectroscopic factors for ten states in ²⁹Si and seven states in ³¹P have been deduced and are compared with other work. The extent to which the data defines the ³He spin-orbit potential is discussed.     

An unambiguous Jπ assignment from γ-rays produced in heavy-ion reactions; The lowest Jπ=6+, 38Ar level

Angular correlation measurements with a Compton-suppression spectrometer in combination with polarization measurements with a three-crystal Ge(Li) Compton polarimeter of γ-rays produced in the ${}^{24}\text{Mg(}{}^{16}\text{O, 2pγ)}{}^{38}\text{Ar}$ reaction result in an unambiguous J^π = 6⁺ assignment to the 6408.3 ± level. It is exclusive decay to the 5^?, 4.59 MeV level is discussed.     

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?.     

The (6Li, 6He) spin-isospin-flip reaction

A formulation of the (⁶Li, ⁶He) spin-isospin-flip scattering problem is presented. The method is applicable to quasielastic collisions between⁶Li described in pureLS coupling scheme and any target nucleus which can be described in a shell model or an adiabatic deformed-nucleus model picture. The effective interaction responsible for the (⁶Li, ⁶He) reaction involves an integration of the (σ₁ · σ₂) (ρ₁ · ρ₂) compo nent of the central part and the (τ₁· τ₂) tensor part of the nucleon-nucleon interaction over the internal wave function of the projectile. The ⁴⁸Ca(⁶Li,⁶He)⁴⁸Sc reaction populating the ($\text{πf}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{νf}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$) multiplet in ⁴⁸Sc is analysed. It that the tensor force makes some contribution to the transitions to high spin states.     

SU(6) × SL(3, R) color quark model

A nonrelativistic color quark model based on the spectrum generating group SU(6)×SL(3, R) is presented. The model unifies SU(6) and the Regge classification with linear L vs m² mass spectrum. Baryons are predicted to belong to the ($\text{56}\text{, L}{}^{\mathrm{P}}\text{= (}\text{even}{}^{\mathrm{+}}\text{)}\text{and}\text{(}\text{70}\text{, L}{}^{\mathrm{P}}\text{= (}\text{odd}{}^{\mathrm{?}}\text{)}$ multiplets of the SU (6) × O(3) group.     

Multi-step processes in the interpretation of the 28Si(d, 3He)27Al reaction

Results from a CCBA analysis of the ²⁸Si(d, ³He)²⁷Al reaction are reported. The transfers are assumed to occur between dominant components of (λμ) symmetry (0, 12) and (2, 10) in the initial and final nuclear eigenstates respectively. The results show that cross sections to four of the six levels observed below 3 MeV can be fairly well reproduced within a pure K_(J) band framework. However, consistent with electromagnetic results, all six levels can be fit if the K_(J) band purity of the analysis, SU(3) model. $\text{5}\text{2}{}^{\mathrm{+}}\text{(}\text{ground and}\text{2.73}\text{MeV}\text{)}$ states and $\text{9}\text{2}{}^{\mathrm{+}}\text{(3.00}\text{MeV}\text{)}$ state is abandoned.     

Two-step processes in the 40Ca(α, 3He)41Ca reaction

The ⁴⁰Ca(α, ³He) reaction has been studied at 36 MeV incident energy. About fifty levels have been observed up to 7.1 MeV excitation energy and angular distributions were measured from 6–60° using a split-pole spectrometer. A local zero-range DWBA analysis has been carried out, and the deduced l-assignments and spectroscopic factors are compared with those obtained from previous neutron stripping experiments. Core-excited states in ⁴¹Ca with a [3^? ? f_7,2], [2⁺ ? f_7,2] and [5^? ? f_7,2] component previously observed in inelastic scattering experiments, are selectively excited by the (α, ³He) reaction. Their angular distributions are compared with coupled-reaction-channel calculations, assuming a pure two-step reaction mechanism. The agreement between theory and experiment may be considered as rather satisfactory for a number of levels. In particular the $\text{1}\text{2}{}^{\mathrm{+}}\text{and}\text{3}\text{2}{}^{\mathrm{+}}$ levels and the high-spin states with $\text{J}{}^{\mathrm{\pi }}\text{=}\text{9}\text{2}{}^{\mathrm{?}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{,}\text{15}\text{2}{}^{\mathrm{+}}\text{and}\text{17}\text{2}{}^{\mathrm{+}}$ are successfully described within the framework of the weak-coupling model.     

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.     

Rotation-vibration analysis of the Coriolis-coupled ν5g, ν6g, ν8g and ν9 bands of H2CCO

Medium resolution infrared grating spectra of gaseous ketene, H₂CCO were recorded between 1000 and 400 cm^?1, both at instrument temperature (40°C) and with cooling (?40°C). Interferometric Fourier spectra were also measured at ?70°C with resolution 0.22 cm^?1 between 450 and 330 cm^?1. The K structure of the fundamentals ν₅, ν₆, ν₈, and ν₉ was assigned. These fundamentals are coupled by a-axis Coriolis interactions. These couplings were analysed on the symmetric top basis for setting up the perturbation matrix and by utilizing the K-dependent Coriolis shifts of levels. A preliminary analysis of the Coriolis intensity anomalies was also undertaken.Band center values from combination differences are $\text{ν}{}_5{}^0\text{= 587.30 (27)}$ and $\text{ν}{}_6{}^0\text{= 528.36 (39)}\text{cm}{}^{\mathrm{?1}}$. Synthetic spectra indicate the band origins of ν₈ and ν₉ to be close to 977.8 and 439.0 cm^?1, respectively. Estimates of Coriolis coupling constants obtained from synthetic spectra are $\text{ζ}{}_{58}{}^{\mathrm{a}}\text{= + 0.33 (5)}$, $\text{ζ}{}_{68}{}^{\mathrm{a}}\text{= + 0.714 (20)}$, $\text{ζ}{}_{59}{}^{\mathrm{a}}\text{= ? 0.774 (20)}$, and $\text{ζ}{}_{69}{}^{\mathrm{a}}\text{= ? 0.30 (2)}$. Approximate ratios of unperturbed vibrational transition moments obtained from spectral simulations are $\text{M}{}_8{}^0\text{:±iM}{}_5{}^0\text{:±iM}{}_6{}^0\text{:M}{}_9{}^0\text{≈ +2:?9:+10:+0.5}$.     

High spin collective excitations in 101Ru

The energy level structure of ¹⁰¹Ru was studied using the reactions ¹⁰⁰Mo(α, 3n)¹⁰¹Ru and ¹⁰⁰Mo(³He, 2n)¹⁰¹Ru. Excitation functions, γγ coincidences and γ-ray angular distributions were measured. Three ΔI = 2 cascades proceeding to a $\text{5}\text{2}{}^{\mathrm{+}}$, $\text{7}\text{2}{}^{\mathrm{+}}$ and $\text{11}\text{2}{}^{\mathrm{?}}$ state were observed. A decay scheme is presented showing energies up to 5849 keV and spins up to $\text{35}\text{2}$. The bands are discussed within the framework of the Nilsson model with Coriolis coupling in which the recoil effect has been properly introduced.     

Coherent pion production in 3He3He collisions

A model is proposed to describe the near-threshold production of pions in the ${}^3\text{He}\text{(}{}^3\text{He}\text{, π}{}^{\mathrm{+}}\text{)}{}^6\text{Li}$ reaction. Taking experimental data on the ${}^3\text{He}\text{(p, π}{}^{\mathrm{+}}\text{)}{}^4$He process as input the cross sections for the first three levels of ⁶Li are reproduced semi-quantitatively.