The decays of 121g,mCd to 121In

The decay of isotope-separated activities of ¹²¹Cd produced in fission have been studied by γ-ray and conversion-electron spectroscopy. A level scheme of ¹²¹In has been constructed. Transition probabilities between some levels have been deduced from a lifetime measurement. The experimental results are compared to a recent theoretical study of ¹²¹In.     

Beta-delayed proton emission from 97Cd and 99Cd

Two new β-delayed proton precursors, ^97,99Cd, have been identified at the ISOLDE on-line isotope separator. The proton branching ratio for ⁹⁹Cd is (1.7^+1.1_?0.5) × 10^?3. The ⁹⁹Cd proton spectrum is discussed in terms of the statistical model with Porter-Thomas fluctuations. The half-life of ⁹⁹Cd was determined to be 16±3 sec. A search for ⁹⁸Cd was also performed and it was found to be a pure β-emitter with a probable half-life of ≈ 8 sec.     

Differential cross sections for radiative capture of energetic protons by 110Cd and 115In

Spectra of high-energy photons following the radiative capture of 8–22 MeV protons in ¹¹⁰Cd and ¹¹¹In are measured. The (p, γ) differential cross sections at 90° with respect to the beam axis is deduced from the integration of measured spectra. The photon angular distribution is measured for the ${}^{110}\text{Cd}\text{(}\text{p}\text{, γ}{}_0\text{)}$ reaction, too, at 13 MeV incident energy. Satisfactory agreement between theory and experiment is obtained by using the direct-semidirect model for dipole and quadrupole fast nucleon radiative capture.     

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.     

Levels and transition probabilities in 121Cd

The decay of isotope-separated ¹²¹Ag has been studied. A level scheme for ¹²¹Cd has been constructed. Information on lifetimes of excited states has been obtained by the method of delayed coincidences. Some low-lying energy levels of ¹²¹Cd show a considerable deviation from the systematics of similar levels in the lighter isotopes of Cd. This may be attributed to a different spatial symmetry of ¹²¹Cd.     

Nuclear orientation of 160Tb in Tb metal

The decay of ¹⁶⁰Tb oriented at low temperatures in Tb metal has been investigated, and angular distributions of 19 γ-rays have been determined. The reduction in anisotropy in polycrystalline metal samples is discussed. Multipole mixing ratios have been determined for many of the γ-rays. A critical discussion is given of the previously reported $\text{M2}\text{E1}$ mixing ratios, and previous nuclear orientation studies are re-analyzed in a consistent manner so that their results can be compared. It is shown that the nuclear orientation and angular correlation results for the 1178 keV transition are consistent only if E3/E1 mixing is present. The El branching ratios and $\text{M2}\text{E1}$ mixing ratios are analyzed on the basis of Coriolis-mixed K = 0, 1 and 2 character for the negative-parity levels of ¹⁶⁰Dy.     

Nuclear magnetic moment of the 9.7 h 12− isomer 196mAu

The magnetic hyperfine splitting v_M=|gμ_NB_HF/h| of ^196mAu (j^π=12^?; configuration ¦(π$\text{11}\text{2}$($\text{v}\text{13}\text{2}{}^{\mathrm{+}}\text{)〉}{}_{12}{}^{\mathrm{?}}$; $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 9.7}\text{h}\text{)}$ as dilute impurity in Ni has been determined with nuclear magnetic resonance on oriented nuclei as 96.0(2) MHz. With the known hyperfine field B_HF = ?264.4(3.9) kG corrected for hyperfine anomalies the g-factor and magnetic moment of ^196mAu are deduced to be |g| = 0.476(7) and |μ| = 5.72(8) μ_N. Taking into account the known magnetic properties of $\text{π}\text{1}\text{2}{}^{\mathrm{?}}$ and $\text{v}\text{13}\text{2}{}^{\mathrm{+}}$ isomeric states in the neighbouring odd Pt, Au and Hg nuclei the structure of the 12^? state is discussed.     

Selective site occupancy of 117Cd in beryllium

Radioactive ¹¹⁷Cd was implanted in beryllium single crystal along the (0001) and 〈0001〉 crystal directions. Two different quadrupole interaction frequencies for the ¹¹⁷In probe nuclei formed in the decay of ¹¹⁷Cd were observed. It is suggested that implantation along (0001) channels the probe nuclei to the tetrahedral interstitial site while implantation along the 〈0001〉 direction may force the impurity to occupy substitutional sites.     

The importance of intruder states in 114Cd

The origin and decay properties of levels in ¹¹⁴Cd, with special emphasis on the quintuplet of states around 1.2 MeV excitation energy, are invesigated both theoretically and experimentally. An almost complete set of reduced transition probabilities B(E0) and B(E2) is established by means of (n, γ) and (n, e^?) spectroscopy. Cofiguration mixing between vibrational-like and rotational-like states, extracted from proton two-particle-two-hole (2p-2h) core coupling calculations, is found to be crucial for explaining the peculiar level properties.     

Nuclear structure studies of 97Ru from the decay of 97g,mRh

The energy levels of ⁹⁷Ru have been studied through the decay of 31.1 min ^97gRh and 44.3 min ^97mRh using Ge(Li), Si(Li), Nal, plastic and anthracene detectors in singles and in coincidence experiments. A total of 139 γ-rays were observed. Ninety-eight γ-rays have been placed into the decay schemes involving 38 excited levels in ⁹⁷Ru. The level energy of ^97mRh was determined to be 258.6 keV. The spin and parity of ^97gRh and ^97mRh are assigned as $\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{1}\text{2}{}^{\mathrm{?}}$, respectively. The fraction of decay of the isomer by the isomeric transition was measured with the Si(Li) detector, and α_k values were determined for strong transitions. The half-life of the 188.6 keV, $\text{3}\text{2}{}^{\mathrm{+}}$ state in ⁹⁷Ru was determined as 0.23 ± 0.02 ns by delayed e-γ coincidence measurements. The nuclear structure of low-lying levels is compared with similar levels in other odd-mass nuclei (N = 53) isotones and Ru isotopes).     

Proton inelastic scattering from 110Cd and 112Cd at isobaric analog resonances and analysis with the quasiparticle random-phase approximation

Excitation functions for elastic and inelastic scattering of protons from ¹¹⁰Cd and ¹¹²Cd have been measured in the energy ranges of 5.8–8.1 MeV in ¹¹⁰Cd and 6.1–8.4 MeV in ¹¹²Cd. Elastic resonance data have been analyzed using the many-level formula of modified R-matrix theory. Angular distributions have been measured at four prominent inelastic resonances- The results are compared with spectroscopic predictions deduced from calculations using the quasiparticle randomphase approximation (QRPA). The contributions of two different modes arising from the 2p-1h character of the analog state and from the particle-core coupling nature of the parent state were deduced in a microscopic picture. The interference between the resonance and direct scattering has a marked effect on the inelastic angular distributions.     

Measurement of compound-nucleus lifetime by X-ray spectroscopy in the 106Cd(p,p')106Cd reaction

A new method for measuring compound-nucleus lifetimes in the range of 10^?18–10^?16 s is presented. The method is based on the comparison between the known lifetime of an atomic excited state used as a reference and the nuclear delay time to be measured. On-line coincidences performed between the nuclear reaction products and the emitted X-rays enable the selection of the atomic vacancies decaying during the compound stage of the nuclear interaction. The main characteristics of this technique are illustrated by measurements of lifetimes of the ¹⁰⁷In compound nucleus excited at 13.6 and 15.6 MeV in the ¹⁰⁶Cd(p, p')¹⁰⁶Cd reaction. They are found in agreement with statistical model calculations. The spurious effect associated with decay by internal conversion of final states populated by the competitive (p, n) reaction is emphasized.     

Nuclear orientation study of the decay of 171Lu

The levels and γ-ray transitions in ¹⁷¹Yb have been studied by radioactive decay of oriented ¹⁷¹ Lu. The orientation was produced using the hyperfine field in ferromagnetic gadolinium to polarize an ensemble of ¹⁷¹Lu nuclei at a temperature of 14mK. The directional distribution of the γ-rays was measured using high-resolution Ge(Li) detectors. Anisotropies of 30 γ-rays in ¹⁷¹Yb were measured. Multipole mixing ratios were deduced for most of the mixed γ-ray transitions and unambiguous spin assignments were made for several levels.The energy and structure of the rotational band levels, reduced E2 and M1 transition probabilities and E2/M1 mixing ratios were calculated using the semi-microscopic quasiparticle-phonon model with a Coriolis interaction. In general, good agreement is obtained between the theoretical predictions and experimental results.     

Nuclear orientation of negative parity states of 131Xe

The anisotropies of the 177, 326, and 503 keV γ-transitions between negative parity states of ¹³¹Xe have been remeasured in the decay of oriented ¹³¹I nuclei. In addition the linear polarization of the 503 keV radiation has been determined with a Compton polarimeter consisting of two Ge(Li) detectors. A combined analysis of the reported experiment and earlier internal conversion and angular distribution data yields the unique assignments $\text{9}\text{2}{}^{\mathrm{?}}\text{and}\text{7}\text{2}{}^{\mathrm{?}}$ for the levels at 341 and 667 keV. The $\text{E2}\text{M1}$ mixing ratios of the 177 and 326 keV transitions are δ(177) = ?4.5 ± 1.5 and δ(326) = ?4.4 ± 1.6. The intensity of the L = 2 component in the first forbidden β-decay to the 667 keV level is at most 60 %.     

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 $\text{[π(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?2}}{}_{\mathrm{8+}}\text{ν(}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^1\text{]}{}_{\mathrm{<mtext>21</mtext><mtext>2</mtext>}}{}^{\mathrm{+}}$.     

Levels and transition probabilities in 124In as observed in the decay of 124Cd

The levels of ¹²⁴In, which are populated in the decay of ¹²⁴Cd, have been investigated at the OSIRIS on-line facility by means of conversion electron and γ-ray spectroscopy. A γ-γ coincidence measurement combined with the deduced transition intensities permitted construction of a unique level scheme. The half-life of the 243 keV level of ¹²⁴In has been determined to be 50 ± 6 ns by the method of delayed coincidences.     

Hole-vibration states in 115In

The hole-vibration coupling in the Z = 50 region is investigated by calculating the level structure of ¹¹⁵In. Four proton-hole states are coupled with quadrupole and octupole core vibrations. The phonon energies and the amplitudes of the vibrational motions are taken from experiment, while the single-hole energies are treated as free parameters. Most of the observed features of a quintet of states with $\text{I}{}^{\mathrm{\pi }}\text{=}\text{5}\text{2}{}^{\mathrm{+}}\text{,}\text{7}\text{2}{}^{\mathrm{+}}\text{,}\text{9}\text{2}{}^{\mathrm{+}}\text{,}\text{11}\text{2}{}^{\mathrm{+}}\text{,}\text{13}\text{2}{}^{\mathrm{+}}$, which have enhanced E2 transition strengths to the ground state, are well reproduced by the theory. The hole-vibration coupling produces a strong fragmentation of the single-hole strengths. This is quite in agreement with the results of (d, ³He) experiments on ¹¹⁶Sn.     

Coulomb excitation of 115Sn

Coulomb excitation of the nucleus ¹¹⁵Sn was studied with beams of ⁴He and ¹⁶O. Level energies, spins, mean-lives and B(E2) and B(M1) transition probabilities were obtained. Spin $\text{3}\text{2}$⁺ states were observed at 497.35 and 1280.08 keV and spin $\text{5}\text{2}$⁺ states were observed at 986.54 and 1416.78 keV. A state of 612.79 keV was observed to be indirectly excited by decay of the Coulomb excited states. Eleven B(E2) values and nine B(M1) values were obtained for the transitions between the low-lying states. In contrast to previous particle transfer results which suggested a clear distinction between shell-model and collective $\text{3}\text{2}$⁺ and $\text{5}\text{2}$⁺ states, our results suggest the collective strength is shared by the two $\text{3}\text{2}$⁺ and two $\text{5}\text{2}$⁺ states.     

Cross sections for 197Au(n, γ)198Au and 115In(n, γ)116mIn in the neutron energy region 2.0–7.7 MeV

The cross sections for the reactions ¹⁹⁷Au(n, γ)¹⁹⁸Au and ¹¹⁵In(n, γ)^116mIn have been measured with the activation method in the neutron energy region 2.0–7.7 MeV. The influence of background neutrons on the results was studied in considerable detail. The main problems are caused by low-energy neutrons produced by charged-particle reactions in the target material and secondary neutrons from nonelastic reactions in the sample and surrounding materials.The measured capture cross sections are generally lower than previous results and the deviation tends to increase with increasing neutron energy. The data are also compared with calculations based on the compound-nucleus model and quite good agreement is obtained.