A combination magnetic plus Si(Li)-Si(Li) sum-coincidence technique for in-beam studies of internal pair transitions

Abstract An intermediate-image magnetic plus Si(Li) combination pair spectrometer featuring an excellent energy resolution and a pair-line efficiency of 10 −3 , recently presented and demonstrated, has been made more universally applicable by reducing the background underlying the pair lines. The best background reduction is achieved by using two standard Si(Li) detectors and a sum-coincidence method. An experimental coincidence pair-line efficiency of 2.1 × 10 −4 for the 1911 keV E0 pair line in 64 Zn is achieved. In this typical case, the high-energy background (mainly caused by β + activity) is reduced by a factor of about 200 as compared with the direct spectrum of a single detector.

Structure of 106In nucleus

Abstract Single-γ, γγ-coincidence, and γ-ray angular distribution spectra of the 106Cd(p, nγ)106In reaction were measured with Ge(HP), Ge(Li), and Ge(LEPS) detectors at various bombarding proton energies between 8 and 11 MeV. Altogether 141 (among them 117 new) transitions have been assigned to 106In. The conversion electrons were studied with an intermediate-image magnetic spectrometer plus Si(Li) detector, as well as with a superconducting magnetic lens combined with a Si(Li) detector. Internal conversion coefficients have been determined for 22 transitions. A more complete level scheme of 106In, containing 49 levels below 1650 keV excitation energy, has been proposed. On the basis of the…

Decay of 0 2 + states in88,92,94Zr andE0 systematics of Zr isotopes

Branching ratios ofE0 andE2 transitions depopulating the 0 2 + states of88, 92, 94Zr have been determined using conversion-electron and γ-ray spectroscopy. Two different lifetime-measurement methods were applied in the remeasurement of the half-lives of the 0 2 + states in92, 94Zr, yielding consistent results ofT 1/2(0 2 + ,92Zr)=85(15) ps andT 1/2(0 2 + ,94Zr)=280(40) ps. The monopole strengths extracted areρ 2(92Zr)=8.4(17) ×10−3 andρ 2(94Zr)=11.9(20)×10−3. The proton configurations of the 0 2 + states are discussed in view of these values and proton transfer data.

A walk-free centroid method for lifetime measurements with pulsed beams

Abstract A delayed-coincidence lifetime measurement method based on a comparison of walk-free centroids of time spectra is presented. The time is measured between the cyclotron rf signal and the pulse from a plastic scintillation detector followed by a fixed energy selection. The events to be time-analyzed are selected from the associated charge-particle spectrum of a silicon detector which is operated in coincidence with the scintillator, i.e. independently of the formation of the signal containing the time information. With this technique, with the micropulse fwhm of typically 500 to 700 ps, half-lives down to the 10 ps region can be measured. The following half-lives are obtained with th…

A method for high-resolution in-beam studies of internal pair transitions

Abstract A combination intermediate-image magnetic plus Si(Li) electron spectrometer has been adapted to internal pair formation measurements of cyclotron-induced reactions. The system is especially intended for the study of E0 transitions in the energy range from 1.5 to 8.6 MeV and to measurements of coincidences between internal pairs and heavy particles. The method is based on the fact that the electron and the positron spiral from the target to the detector simultaneously, the sense of rotation being of opposite sign. The energies of the particles are summed in a high-resolution cooled Si(Li) detector. Calculations of the spectrometer pair-line efficiency for E0 transitions versus trans…

Systematic study of low-spin states in even Cd nuclei.

Low-lying low-spin collective states in even $^{106\mathrm{\ensuremath{-}}112}\mathrm{Cd}$ and $^{116}\mathrm{Cd}$ were investigated using in-beam and off-beam \ensuremath{\gamma}-ray and conversion-electron spectroscopy. New spin assignments and decay branching ratios for the levels in $^{106}\mathrm{Cd}$, $^{108}\mathrm{Cd}$, $^{110}\mathrm{Cd}$, and $^{112}\mathrm{Cd}$ were obtained. The present results essentially complement the level systematics from $^{106}\mathrm{Cd}$ to $^{120}\mathrm{Cd}$. From the new data, it is inferred that two sets of low-lying ${0}^{+}$ states having different excitation characteristics cross between $^{114}\mathrm{Cd}$ and $^{116}\mathrm{Cd}$. No correspondi…

AbsoluteE0 andE2 transition rates and collective states in116Sn

AbsoluteE0 andE2 transition rates in116Sn have been measured using several newly developed techniques. ManyE2 transitions are observed to have a collective character withB(E2) values of up to 60 W.u. The presence of deformed excited states in116Sn is discussed in view of the results obtained.

E0study of0+states near 5 MeV in208Pb

Strong E0 lines from the 4866 and 5237 keV ${0}^{+}$ states in $^{208}\mathrm{Pb}$ have been identified using a new high-energy conversion-electron spectrometry technique in the study of the $^{207}\mathrm{Pb}$(d,p${)}^{208}$Pb and $^{208}\mathrm{Pb}$(p,p'${)}^{208}$Pb reactions at ${E}_{\mathrm{d}=10}$ MeV and ${E}_{\mathrm{p}=17.3}$ MeV, respectively. No evidence for an E0 transition from the expected third ${0}^{+}$ state was found.

Structure ofIn112nucleus

The \ensuremath{\gamma}-ray spectra of the $^{112}\mathrm{Cd}$(p,n\ensuremath{\gamma}${)}^{112}$In and $^{109}\mathrm{Ag}$(\ensuremath{\alpha},n\ensuremath{\gamma}${)}^{112}$In reactions were measured with Ge(Li) spectrometers for bombarding energies of 4.8 MeV protons and 17.1 MeV \ensuremath{\alpha} particles. The energies and relative intensities of 79 $^{112}\mathrm{In}$ \ensuremath{\gamma}-ray transitions have been determined. The electron spectra were measured with combined magnet plus Si(Li) as well as superconducting magnetic lens plus Si(Li) spectrometers. Internal conversion coefficients of 40 $^{112}\mathrm{In}$ transitions have been determined, and the level scheme of $^{112}\ma…

New features in systematics of low-spin states in even106?120Cd

Low- spin states in even106–112Cd and116Cd were investigated by in-beam and off-beam γ-ray and conversion electron spectroscopy. New spin assignments and decay branching ratios for the levels in106Cd,108Cd and110Cd were obtained. From the new systematical data for the even106–120Cd, it is inferred that two sets of low-lying 0+ states cross between114Cd and116Cd. One of these sets appears to have features of both intruder and two-quadrupole-phonon states.

First measurement ofK-shell-electron to internal-pair conversion probability ratios forE0 transitions inf p shell region

Magnetic plus Si(Li) spectrometers designed for high-resolution conversion-electron and internal-pair measurements, are employed to obtainK-shell-electron to internal-pair conversion probability ratios forE0 transitions in54Fe,60Ni,64Zn and70Ge. The results are found to be in good agreement with theoretical predictions.

A semiconductor detector telescope electron spectrometer

Abstract A simple d E d x+E type semiconductor detector telescope electron spectrometer featuring high detection efficiency and effective discrimination against γ-rays and heavy particles is described. The line shape of the spectrometer is better than that of a single detector of corresponding size; at 1 MeV, the peak-to-total ratio is approximately 0.8. The device is suited to the study of beta-ray spectra and conversion electron lines at energies above about 0.4 MeV.

A combination intermediate-image magnetic plus Si(Li) electron spectrometer for in-beam experiments

Abstract A magnetic lens plus Si(Li) combination in-beam beta spectrometer with focusing properties and field shape similar to those of an intermediate-image spectrometer is described. A high transmission and a large momentum band-width are achieved by placing both the target and the detector in a high magnetic field inside the lens. The beam enters the lens axially, and the Faraday cup is placed inside the lens. The spectrometer is well suited to singles conversion-electron spectroscopy, to electron-heavy particle coincidence measurements, to lifetime measurements and to studies of internal-pair transitions.

A swept-current magnetic lens plus Si(Li) electron spectrometer with simultaneous momentum and energy selection

Abstract A combined swept-current magnetic lens plus Si(Li) electron spectrometer with simultaneous momentum and energy selection is presented. The spectrometer is intended for in-beam measurements of conversion electron lines up to several MeV in energy and for nanosecond lifetime determinations, as well as for off-beam studies of continuous beta-ray spectra and conversion lines from short-lived activities. The sweeping of the lens current is automatized and the energy selection, synchronously with the momentum, is performed using a simple digital window arrangement. The performance of the spectrometer is demonstrated in conversion electron and continuous spectrum measurements. Different v…

Collective states in 116Sn

Electromagnetic properties of low-spin states in102, 104Pd

Electromagnetic transitions from low-lying 0+, 2+, 4+ and 3− states in102, 104Pd have been studied using (p, 2n) and (p, p′) reactions and Coulomb excitation. TheE2 transition probabilities from the 0 3 + state in102Pd (13 W.u.) and from the 02/+ state in104Pd (14 W.u.) are somewhat low for two-phonon states. Generally, theE2 transition rates are reasonably well reproduced by the IBA-2 and by the boson-expansion description. The intruding 0 2 + state (t1/2=14.3 ns) in102Pd is connected to the 22/+ and 2 3 + states via strong E2 transitions: B(E2; 0 2 + → 2 2 + )=96±40 W.u.; B(E2; 2 3 + → 0 2 + =17±11 W.u.

Decay characteristics of 0 2 + and 0 3 + states in112Cd and114Cd

Absolute rates ofE0 andE2 transitions depopulating 0 2 + and 0 3 + states in112Cd and114Cd have been determined using conversion-electron andγ-ray spectroscopy, and double Coulomb excitation. The collectivity of these states is established and discussed.

New Features in the Systematics of Low‐Spin States in Even 106‐120Cd

Low‐spin states in even 106‐112Cd and 116Cd were investigated by in‐beam and off‐beam γ‐ray and conversion‐electron spectroscopy. New spin assignments and decay branching ratios for the levels in 106Cd,108Cd,110Cd and 112Cd were obtained. From the new systematical data for the even 106‐120Cd, it is inferred that two sets of low‐lying 0+ states cross between 114Cd and 116Cd. One of these sets appears to have features of both intruder and two‐quadrupole‐phonon states.

Single-Particle Excitations and Collective Vibrational Modes in 96Zr

New results from (n,n’γ) and (p,p’γ) reactions, as well as from β- decay confirm the double subshell closure in 96Zr and provide a detailed level scheme for this nucleus. The 1750 keV first 2+ state is described as a neutron particle-hole excitation, while the positive-parity band built on the 1582 keV excited 0+ state is characterised by quadrupole vibrational collectivity at low spins. Candidates for two-phonon octupole, quadrupole-octupole and higher multipole states are suggested on the basis of fast El and E2 decays to the 3- octupole state. The recently observed large octupole strength, its inverse relationship with the filling of the νlh11/2 orbital, and the onset of quadrupole defor…