Transitions,with change in parity,produced in 107,109Ag by coulomb excitation

Some of the low-lying energy levels of ¹⁰⁷Ag and ¹⁰⁹Ag were excited by Coulomb excitation using α-particles from 4.8 to 7.2 MeV. Transitions to the isomeric state ($\text{7}\text{2}{}^{\mathrm{+}}$), involving a parity change, were observed both directly in the singles spectra and indirectly by the decay of the isomer. The isomer in both silver isotopes was populated by transitions from the $\text{5}\text{2}{}^{\mathrm{?}}$ level, which was strongly excited. The observed branching ratio in ¹⁰⁹Ag for the $\text{5}\text{2}{}^{\mathrm{?}}\text{→}\text{7}\text{2}{}^{\mathrm{+}}$ transition was (0.315 ± 0.09) % and for the $\text{5}\text{2}{}^{\mathrm{?}}\text{→}\text{9}\text{2}{}^{\mathrm{+}}$ transition was (0.055±0.03) %. The total rate of populating the $\text{7}\text{2}{}^{\mathrm{+}}$ level from the $\text{5}\text{2}{}^{\mathrm{?}}$ level was (0.215±0.04) % in ¹⁰⁷Ag. The level schemes have been discussed on the weak-coupling model, allowing admixtures of singleparticle wave functions to account for the weaker transitions.     

Magnetic moment and half-life of the isomeric 112− state in 107Cd

An isomeric level in ¹⁰⁷Cd at 845 keV populated by the reactions ¹⁰⁷Ag(p, n), ¹⁰⁶Cd(d, p) and ¹⁰⁴Pd(α, n) has been observed. The half-life of this state is $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 77(7)}\text{ns}$, and the spin and parity are $\text{I}{}^{\mathrm{\pi }}\text{=}\text{11}\text{2}{}^{\mathrm{?}}$. The magnetic moment has been determined by the pulsed beam time-differential perturbed angular distribution method (DPAD) to be μ = ?1.012(12) n.m.     

Spectroscopic study of 15N states with the reaction 14C(d,n)

Energy and angular distributions of neutrons from the reaction ¹⁴C(d, n)¹⁵N have been measured at 6.5 MeV deuteron energy. The DWBA analysis yielded l-values and absolute spectroscopic factors for fifteen states in ¹⁵N below 10 MeV excitation energy. For the 9.23 MeV level J^π is determined to be $\text{3}\text{2}$⁺ or $\text{5}\text{2}$⁺, for the 9.93 MeV level the data suggest $\text{J}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$. The spectroscopic factors are in qualitative agreement with pure jj coupling and in semi-quantitative agreement with shell-model calculations.     

Level structure in 117Sb investigated in the decay of the isomeric three-quasiparticle state

The level structure of ¹¹⁷Sb was investigated in the reactions ¹¹⁵In(α, 2nγ)^117mSb, ¹¹⁷Sn(d, 2nγ)^117mSb and ¹¹⁷Sn(p, nγ)^117mSb. In order to confirm level sequences and to assign spins and parities to levels populated in the decay of the isomeric three-particle state $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ = 340 μs), prompt and delayed γ-ray spectra, lifetimes, γ-γ coincidences, γ-ray angular distributions, conversion electrons and excitation functions were measured. The spin $\text{25}\text{2}$⁺ of the isomeric state can be explained by the three-particle configuration [$\text{π(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{); v(}\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}\text{)}{}^2\text{10}{}^{\mathrm{+}}\text{]}\text{25}\text{2}{}^{\mathrm{+}}$. This is supported by the experimentally determined g-factor of g = O.115 ± 0.006. Other levels in ¹¹⁷Sb can be interpreted as particle states coupled to anharmonic vibrations of the core. The existence of an excited $\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$ quasirotational band is experimentally proved and is supported by calculations of the equilibrium deformation.     

Observation of isomeric states and band structures in 107Cd

The odd-mass nucleus ¹⁰⁷Cd was investigated in the reactions ${}^{105}\text{Pd}\text{(α, 2}\text{n}\text{)}{}^{107}\text{Cd}\text{,}{}^{107}\text{Ag}\text{(d, 2}\text{n}\text{)}{}^{107}\text{Cd and}{}^{107}\text{Ag}\text{(}\text{p, n}\text{)}{}^{107}\text{Cd}$. The constructed level scheme is based on results, obtained from singles γ-ray spectra and excitation functions, from the measurements of delayed γ-rays, of γ-γ coincidences, of internal conversion electrons and of γ-ray angular distributions. Two new isomers were observed. The first one, interpreted as the $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ neutron state at 845.6 keV has a half-life of 67 ± 6 ns. This isomeric state is populated by a strong E2 cascade. Bands built on the other intrinsic states with spins and parities $\text{5}\text{2}{}^{\mathrm{+}}$ and $\text{7}\text{2}{}^{\mathrm{+}}$ are not strongly populated. For the second isomeric state at an excitation energy of 2679 keV a half-life of 55±4 ns was determined. This isomer is probably a three-quasiparticle state. Its configuration can be proposed as $\text{[π(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}{}_{\mathrm{8+}}\text{ν(}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^1\text{]}{}_{\mathrm{<mtext>21</mtext><mtext>2</mtext>}}{}^{\mathrm{+}}$.     

Photoproduction of charged π mesons from protons and neutrons in the energy range between 250 and 790 MeV

The differential cross sections for γp→π⁺n from hydrogen and the $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ ratios from deuterium were measured at nine c.m. angles between 30° and 150° for laboratory photon energies between 260 and 800 MeV. A magnetic spectrometer with three layers of scintillation hodoscope was used to detect charged π mesons. The cross section for γn→π^?p was obtained as a product of $\text{d}\text{σ}\text{d}\text{Ω}\text{(γ}\text{p}\text{→π}{}^{\mathrm{+}}\text{n}\text{)}$ and the $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$ ratio. The overall features in the cross sections of the two reactions, γp→π⁺n and γn→π^?p, and in the ratios, $\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}$, agree with predictions by Moorhouse, Oberlack and Rosenfeld, and Metcalf and Walker. An investigation of the possible existence of an isotensor current was made and a negative result was found. In detailed balance comparison with the new results on the inverse reaction π^?p→γn, no apparent violation of time-reversal invariance was observed.     

Gamma decay of positive-parity levels in 45Ti from the 42Ca(α, nγ)45Ti reaction

Gamma-ray angular distributions, nγ angular correlations, γγ coincidences and Doppler-shift attenuations have been measured in the ⁴²Ca(α, nγ)⁴⁵Ti reaction. In addition to the known positive-parity levels forming the $\text{K}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{+}}\text{band, the}\text{K}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{+}}$ band members are identified in ⁴⁵Ti. They are the $\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{3}\text{2}{}^{\mathrm{+}}\text{,}\text{5}\text{2}{}^{\mathrm{+}}\text{and}\text{7}\text{2}{}^{\mathrm{+}}$ levels at 1565 keV, 1958 keV, 2258 Reduced transition probabilities are obtained for the γ-decays of these levels as well as for those of the $\text{K}{}^{\mathrm{\pi }}\text{=}\text{3}\text{2}{}^{\mathrm{+}}$ band members. The excitation energies and transition probabilities are well reproduced by a rotation-particle-coupling model calculation with deformation parameter β = 0.30–0.35.     

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.     

Three-body calculation of the 2H(α, αp)n reaction

The ²H(α, αp)n reaction at 15–42 MeV is analysed by solving the Amado-Lovelace equations. Rank-one separable potentials with the Yamaguchi-type form factor are assumed in ${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$s, ${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$$\text{p and}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{p}$ waves for the N-α subsystem and in the triplet s-wave for the n-p subsystem. The agreement with experiment is quite good in this energy region. The role of multiple-scattering terms is discussed. Interesting features of the reaction mechanism, such as the decay process through the 1⁺ resonance of ⁶Li, are found in this energy region. The triton transfer process at 15 MeV predicted by the modified impulse approximation is not found. The numerical method is discussed. It is shown that the rotated contour method causes no difficulties even when it is applied to breakup amplitudes.     

Wide angle electron-positron bremsstrahlung at adone a new limit for the existence of a heavy electron

The cross section for the reaction e⁺+e^?→e⁺+e^?+γ has been measured at the Adone storage ring. The results in agreement with the QED predictions, establish a new limit for the mass and the coupling constant $\text{e}{}^1\text{e}\text{γ}$ of a heavy electron e¹.     

Gyromagnetic ratios of excited states in 107, 109Ag

The gyromagnetic ratios of the lowest excited $\text{3}\text{2}{}^{\mathrm{?}}\text{and}\text{5}\text{2}{}^{\mathrm{?}}$ states in ^{107, 109}Ag were simultaneously measured relative to that of the 2₁⁺ level in ¹⁰⁸Pd. The thin-foil, perturbed γ-ray angular distribution technique was employed utilizing the transient hyperfine magnetic field present at the nuclei of these ions as they swiftly recoiled through a thin magnetized Co foil. The states of interest were Coulomb-excited using beams of 100 MeV ³²S ions. The present measurements yielded $\text{g(}\text{3}\text{2}{}^{\mathrm{?}}\text{;}{}^{107}\text{Ag}\text{) = +0.63 ± 0.09, g(}\text{5}\text{2}{}^{\mathrm{?}}\text{;}{}^{107}\text{Ag}\text{) = + 0.37±0.06, g(}\text{3}\text{2}{}^{\mathrm{?}}\text{;}{}^{109}\text{Ag}\text{) = +0.77 ± 0.10,}\text{and}\text{g(}\text{5}\text{2}{}^{\mathrm{?}}\text{;}{}^{109}\text{Ag}\text{) = +0.36 ± 0.05}$. These findings are compared with weak-coupling and other appropriate model calculations.     

Simultaneous production of K1o (892) and Δ++(1236) in the reaction K+p→K+π+π−p from 4.3 to 5.0 GeV/c

The reaction $\text{K}{}^{\mathrm{+}}\text{d}\text{→}\text{K}{}^{\mathrm{1o}}\text{(892) Δ}{}^{\mathrm{++}}\text{(1236)}\text{n}{}_{\mathrm{s}}$ from a K⁺d experiment with the CERN 2 m bubble chamber at 4.6 GeV/c is compared with the reaction $\text{K}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^{\mathrm{1o}}\text{(892)Δ}{}^{\mathrm{++}}\text{(1236)}$ from a K⁺p experiment at the same energy. In addition, predictions of an absorption model, a Regge pole model and a quark model for the production and decay characteristics of the reaction $\text{K}{}^{\mathrm{+}}\text{p}\text{→}\text{K}{}^{\mathrm{1o}}\text{(892)Δ}{}^{\mathrm{++}}\text{(1236)}$ are tested with the combined statistics of the K⁺d experiment and three K⁺p experiments between 4.3 and 5.0 GeV/c.     

Low-lying states in 95Tc studied with the 93Nb(α, 2nγ)95Tc reaction

Low-lying states in ⁹⁵Tc were studied with the ⁹³Nb(α, 2nγ)⁹⁵Tc reaction. The level scheme was obtained from the γ-γ coincidence measurement. The spin assignment was made on the basis of the observed γ-ray angular distributions and the excitation functions. The $\text{337}\text{keV}\text{7}\text{2}{}^{\mathrm{+}}\text{, 627}\text{keV}\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{), 882}\text{keV}\text{13}\text{2}{}^{\mathrm{+}}\text{and}\text{957}\text{keV}\text{11}\text{2}{}^{\mathrm{+}}$ states, and possibly state, are found to be strong candidates for the core multiplet states $\text{[(1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>p</mtext>}}\text{?2}{}^{\mathrm{+}}\text{]}{}_{\mathrm{J}}$. These states are discussed in term of a weak coupling model and the dressed three-quasiparticle model. The observed γ-ray angular distributions are compared with expectations based on a simple deexcitation model of the (α, 2nγ) reaction.     

Measured lifetimes of states in 197Au and a critical comparison with the weak-coupling core-excitation model

The lifetimes of five excited states in ¹⁹⁷Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV ²⁰Ne and 120 MeV ³⁵Cl ion beams. The experimentally determined spectroscopy of the low-lying levels $\text{3}\text{2}{}^{\mathrm{+}}$ (ground state) and $\text{1}\text{2}{}^{\mathrm{+}}$, $\text{3}\text{2}{}_2{}^{\mathrm{+}}$, $\text{5}\text{2}{}^{\mathrm{+}}$, and $\text{7}\text{2}{}^{\mathrm{+}}$ at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a $\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ proton hole coupled to a ¹⁹⁸Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates.     

Lifetimes in 103Rh, 107Ag and 109Ag measured by the recoil-distance technique

The lifetimes of the lowest $\text{3}\text{2}{}^{\mathrm{?}}\text{and}\text{5}\text{2}{}^{\mathrm{?}}$ levels in ¹⁰³Rh, ¹⁰⁷Ag and ¹⁰⁹Ag have been measured with the Doppler-shift version of the recoil-distance technique. A beam of ³⁵Cl ions of energy 64 MeV was used to Coulomb excite the target nuclei and eject them from the target. The following lifetimes were obtained: $\text{τ(}{}^{103}\text{Rh}\text{,}\text{3}\text{2}{}^{\mathrm{?}}\text{, 295}\text{keV}\text{) = 14.5 ± 1.5}\text{ps}\text{, ρ}{}^{103}\text{Rh}$, $\text{5}\text{2}{}^{\mathrm{?}}\text{, 357}\text{keV}\text{) = 112 ± 10}\text{ps}\text{; τ(}{}^{107}\text{Ag}$, $\text{3}\text{2}{}^{\mathrm{?}}\text{, 325}\text{keV}\text{) = 7.2 ± 1.3}\text{ps}\text{, τ(}{}^{107}\text{Ag}$, $\text{5}\text{2}{}^{\mathrm{?}}\text{, 423}\text{keV}\text{) = 43 ± 3}\text{ps}\text{; τ(}{}^{109}\text{Ag}$, $\text{3}\text{2}{}^{\mathrm{?}}\text{, 311}\text{keV}\text{) = 8.5 ± 1.0}\text{ps}\text{, τ(}{}^{109}\text{Ag}$, $\text{5}\text{2}{}^{\mathrm{?}}\text{, 415}\text{keV}\text{) = 50 ± 3}\text{ps}$. Of t correction factors taken into account the perturbation of the γ-ray angular distribution by the magnetic hyperfine interaction during recoil through vacuum was found to give the largest correction to the measured lifetimes. These lifetimes lead to reduced transition probabilities B_d(E2) for the silver nuclei in reasonable agreement with the predictions of the core-excitation theory.     

High-spin states in 103Ag and particle-core coupling at intermediate deformation

The ¹⁰³Ag nucleus has been studied using the ¹⁰³Rh(α, 4nγ)¹⁰³Ag and ¹⁰³Rh(³He, 3nγ)¹⁰³Ag reactions. A set of standard in-beam measurements involving relative excitation function measurements of γ-rays, γ-γ-Δt coincidences, conversion electron measurements and angular distribution and linear polarization measurements of emitted γ-rays have been performed. Excited states with spin values up to $\text{27}\text{2}$ are populated in this nucleus. Among these excitations a positive-parity band built on the $\text{J}{}^{\mathrm{\pi }}\text{=}\text{7}\text{2}{}^{\mathrm{+}}\text{or}\text{9}\text{2}{}^{\mathrm{+}}$ state can be distinguished. This band has similar properties as the band observed in ¹⁰⁵Ag. The experimental data on the band in ^{103, 105}Ag are compared to the prediction of the Nilsson model with Coriolis coupling at intermediate deformation ε = 0.10?0.15. Energy levels of the positive-parity bands are reproduced satisfactorily by the calculations assuming either a $\text{K =}\text{7}\text{2}{}^{\mathrm{+}}\text{[413]}\text{or}\text{K =}\text{9}\text{2}{}^{\mathrm{+}}\text{[404]}$ band head. However, electromagnetic properties of the levels, branching and mixing ratios, are better reproduced when assuming the $\text{K =}\text{7}\text{2}{}^{\mathrm{+}}$ band head. Attenuation of the Coriolis interaction was introduced in order to improve the fit of the calculated energies of the levels to the experimental values.     

Core polarization for M2 transitions in odd-A tin isotopes

The reduced M2 transition probabilities $\text{11}\text{2}{}^{\mathrm{?}}{}_1\text{→}\text{7}\text{2}{}^{\mathrm{+}}{}_1$ in the odd-A isotopes ^109–121Sn are found to reveal a specific behaviour. B(M2) values are calculated in the framework of the quasiparticlephonon model. The coupling of a quasineutron with the 2⁺, 3^? and 2^? one-phonon core excitation is taken into account. Inclusion of all one-phonon 2^? states up to 24 MeV in the wave functions of the excited states $\text{11}\text{2}{}^{\mathrm{?}}{}_1\text{and}\text{7}\text{2}{}^{\mathrm{+}}{}_1$ reduces the theoretical B(M2) values by 3–4 times as compared to the single-particle values. The specific B(M2) dependence on the mass number appears to be due to the pairing effect.     

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.