keV Excitation Energy Research Articles

Core excitation in 98Cd

Using a 58Ni(46Ti, α2n) reaction, a total of 24 different residual nuclei were identified. Among them were 98Cd and 97Ag. The level scheme of 98Cd was extended to Jπ=(15+). An isomeric state at 6634 keV excitation energy was confirmed. This state decays by a 4207 keV transition feeding the known 8+ state. The level scheme of 97Ag was also extended to Jπ=(33/2+) and the half-lives of two isomeric states were measured. Experimental energies of the excited states were compared with the results of ab initio shell-model calculations based on a realistic two-nucleon interaction. The Gammasphere Ge array, coupled with the Microball and the Neutron Shell ancillary particle detectors, was used at the 88 inch cyclotron at Lawrence Berkeley National Laboratory, USA.

X-ray photoelectron spectroscopy and diffraction in the hard X-ray regime: Fundamental considerations and future possibilities

The prospects for extending X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD) measurements into the hard X-ray regime of 5–15 keV excitation energies are discussed from a fundamental point of view, in some cases using prior results obtained in the 1–2 keV range as starting points of discussion, together with theoretical estimates of behavior at higher energies. Subjects treated are: the instrumentation improvements needed to optimize peak intensities; the tuning of experimental conditions to achieve bulk or surface sensitivity; the use of grazing incidence to suppress spectral backgrounds; the use of standing waves created by Bragg reflection from crystal planes or synthetic multilayers to achieve position-sensitive densities of states, compositions, and magnetizations; photoelectron diffraction and Kikuchi-band effects as element-specific local structure probes; and valence-level measurements, including the role of non-dipole effects and mechanisms leading to complete Brillouin zone averaging and density-of-states like spectra. Several distinct advantages are found for such high-energy extensions of the XPS and XPD techniques.

A study on the decay of 72 As

The excited states of the 72Ge nucleus were investigated in radioactive decay of 72As. Three new transitions with 1996.58, 2125.59 and 2255.49keV have been found for the first time. One γ-ray with 912.09keV has been placed in the decay scheme for the first time and the placement of 1938.88, 2116.79, 2785.59, 2833.03, 2950.69 and 3338.00keV γ-rays are confirmed again in the present work. One new level at 2027.72keV excitation energy is proposed. The level scheme was established and for a number of levels spin-parity assignments are suggested on the basis of logft values and γ-branching ratios.

LIFETIME MEASUREMENTS OF EXCITED STATES IN 73As

The excited states of 73 As have been investigated via the 73 Ge ( p , n γ)73 As reaction with proton beam energies from 2.5–4.3 MeV. The lifetimes of the levels at 769.6, 860.5, 1177.8, 1188.7, 1274.9, 1344.1, 1557.1 and 1975.2 keV excitation energies have been measured for the first time using the Doppler shift attenuation method. The angular distributions have been used to assign the spins and the multipole mixing ratios using statistical theory for compound nuclear reactions. The ambiguity in the spin values for the various levels has been removed. The multipole mixing ratios for eight γ-transitions have been newly measured.

Isomerism in 96Ag and non-yrast levels in 96Pd and 95Rh, studied in β decay

The β decay of 96Ag ( Z=47, N=49) was investigated by measuring positrons, X rays as well as β-delayed protons and γ rays. The γ radiation was studied by means of germanium detectors and a NaI total-absorption spectrometer. Two β-decaying isomers in 96Ag were established with half-lives of 4.40(6) and 6.9(6) s and tentative spin–parity assignments of (8 +) and (2 +), respectively. For both isomers, the intensities of β transitions to low-lying levels of 96Pd ( Z=46, N=50) and β-delayed proton decays to levels in 95Rh ( Z=45, N=50) were measured. Several new 96Pd levels were firmly established. The level energies, their γ decays and the Gamow–Teller decay of 96Ag are compared to shell-model predictions. A new low-lying level in 95Rh was found at 680 keV excitation energy. Through a comparison with low-lying states of N=50 isotones, this level is interpreted as the first excited 7/2 + state built on the proton 9/2 + ground state. The assignments of further excited states in 95Rh are discussed.

Measurement of X-ray production cross-sections of Ti, V, Cr, Mn, Fe, Co, Ni and Cu molecules

K shell X-ray production cross-sections in the Ti, V, Cr, Mn, Fe, Co, Ni, and Cu in the molecules were studied at 59.5 keV excitation energy by using a Si(Li) detector ( FWHM = 155 eV at 5.96 keV). The present results are compared with other theoretical values.

LIFETIMES OF LEVELS IN 71Ge

The low-lying states of 71Ge have been studied the via the 71Ga (p,n γ)71Ge reaction using proton beam energies of 2.5–4.3 MeV. The angular distributions have been used to assign the spins and the multipole mixing ratios using statistical theory for compound nuclear reactions. The ambiguity in the spin values for the various levels has been removed. The multipole mixing ratios for a few γ-transitions have been newly measured. The lifetimes of the levels at 747.0, 808.0, 831.1, 1377.8, 1406.6, 1414.4, 1422.1, 1558.8 and 1566.1 keV excitation energies have been measured for the first time using the Doppler shift attenuation method.

A decay study of 70As

The excited states of the 70Ge nucleus in radioactive decay of 70As were investigated. Four new transitions with 1036.99, 1196.66, 1539.29 and 2531.7 keV have been found. The placement of 2219.34 keV transition has been reassigned, three γ-rays with 496.74, 1295.24 and 1417.24 keV have been placed in the decay scheme for the first time, and the placements of 1881.67, 2325.42 and 2424.41 keV γ-rays are confirmed in the present work. Two new levels at 4243.10 and 5265.81 keV excitation energy, respectively, are proposed. The level scheme was established and for a number of levels spin-parity assignments are suggested on the basis of log ft values and γ-branching ratios.

Measurement of L x-ray Production Cross-sections at 5.96 keV and Average L and M Shell Fluorescence Yields of Elements in the Atomic Number Range 40 ≤ Z ≤ 55

L x-ray production cross-sections for 12 elements were measured at 5.96 keV excitation energy in the atomic number range 40 ≤ Z ≤ 55. The average L shell fluorescence yields of these elements have been evaluated by using the presently measured cross-section values and the theoretical L shell photoionisation cross-section values at the same energy. The average M shell fluorescence yields were evaluated using the line widths of L x-ray and level widths of L and M shells.

Determination of Coster–Kronig transition probabilities (L1 → L2, L1 → L3 and L2 → L3) for Hg and Bi in molecules

AbstractThe f12, f13 and f23 Coster–Kronig (CK) transitions (that is L1 → L2, L1 → L3 and L2 → L3 transitions) in Hg and Bi in molecules were studied at 59.5 keV excitation energy using an Si(Li) detector. A change in the CK transition probabilities was observed for different molecules. The change in the values for Hg compounds were greater than those for Bi compounds. Because we did not have pure Bi in the laboratory and also were not able to have specimen preparation conditions for pure Hg, we did not obtain experimental values for elemental Bi and Hg. Copyright © 2002 John Wiley & Sons, Ltd.

Energy levels in [formula omitted] from the decay of [formula omitted

The γ-ray spectrum of 139La following the β− decay of 139Ba has been studied using both singles and γγ coincidence spectroscopy techniques. The energies and intensities of 30 γ-transitions have been determined, which include three new transitions placed in the level scheme. Two new levels at 1524.6 and 1900.3keV excitation energies are proposed and a number of γ-transitions have been confirmed. On the basis of these results a precise decay scheme is proposed.

Isomeric state of 80Y and its role in the astrophysical rp-process

A careful investigation of the isomeric transition of the long-lived state at 228.5 keV excitation energy in 80Y has been done. The HIGISOL facility at the Jyvaskyla isochronous cyclotron has been used. We used the electron magnetic transporter to prepare an appropriate source and to measure the electron spectra in clean background conditions. The measured internal conversion coefficient αK = 0.50±0.07 allows unambiguous 1- identification for the 228.5 keV first excited isomeric state in 80Y. With a “bare" half-life of 6.8±0.5 s found in this work, this state is strongly populated in the rp-process during X-ray bursts and has therefore to be taken into account in X-ray burst model calculations. However, because of the similarity of the β-decay half-lives of isomeric and ground states, we find a maximum reduction in the effective β-decay lifetime of 80Y of only 17±2%. Our results pave the way for a future investigation of the impact of the isomeric state on the “effective" 80Y proton capture rate.

Observation of the Molecular Quenching of μp(2S) Atoms

Kinetic energy distributions of muonic hydrogen atoms μp(1S) have been obtained by means of a time-of-flight technique for hydrogen gas pressures between 4 and 64 hPa. A high energy component of ∼900 eV observed in the data is interpreted as the signature of long-lived μp(2S) atoms, which are quenched in a non-radiative process leading to the observed high energy: the collision of a thermalized μp(2S) atom with a hydrogen molecule H2 results in the resonant formation of a {[(ppμ)+]*pee}* molecule. Then the (ppμ)+ complex undergoes Coulomb de-excitation and the ∼1.9 keV excitation energy is shared between a μp(1S) atom and one proton. The preliminary analysis of the time spectra gives a long-lived μp(2S) population of ∼1% of all stopped muons, and a quenching rate of ∼4⋅1011 s−1.

Signature inversion and the first observation of a magnetic dipole band in odd-odd rubidium isotopes:82Rb

High-spin states in ${}^{82}\mathrm{Rb}$ were studied through the ${}^{68}\mathrm{Zn}{(}^{18}\mathrm{O},p3n)$ reaction at 56 MeV beam energy via a thin target coincidence measurement. The known sequence of positive-parity states built on the ${6}^{+}$ state at 191.3 keV was extended up to spin 14, and signature inversion was observed around spin 11. Above spin 8 the observed properties of this band indicate a rotationlike structure. A new high-lying level sequence connected by $\ensuremath{\Delta}I=1$ transitions was identified. This magnetic dipole sequence is built on a new ${(11}^{\ensuremath{-}})$ level at 2617.3 keV excitation energy which is interpreted as a $\ensuremath{\pi}{(g}_{9/2}{)}^{2}\ensuremath{\bigotimes}\ensuremath{\pi}{(p}_{3/2}{,f}_{5/2})\ensuremath{\bigotimes}\ensuremath{\nu}{g}_{9/2}$ four-quasiparticle state at small quadrupole deformation.

Decay of 76As

The level structure of 76Se has been investigated by studying the γ-rays emitted following the β − decay of 76As. The energies and relative intensities of 45 γ-rays have been determined with a better overall precision than previously. Two new transitions with 528.2 and 1232.4 keV have been found and placed in the level scheme. A new level, at 1791.5 keV excitation energy, is proposed. Seven transitions and three levels previously attributed to this decay scheme were not confirmed.

Development of multichannel time scaling technique to analyse the half-life of 75mAs using correlation analysis

We report on the use of a multichannel time scaling technique suitable for determining the half-life of long-lived intermediate states by means of correlation counting. Use of the method is demonstrated by studying the decay of an isomer of at 304 keV excitation energy using a pressurized proportional counter and NaI(Tl) detection set-up. The measurement time was 9000 s. Eighteen values for electron capture detection efficiencies were obtained in the energy region 1.4-12 keV. We obtained eighteen sets of data for determining the fraction of correlation events, each set consisting of 52 counting distributions determined by scanning the clock-time of electron capture events with dwell times varying from 5 ms to 1500 ms. There are four sets acceptable for this work according to our criteria. The half-life of the 304 keV level was determined to be and is compared with earlier results.

Decay of 129Nd to low-lying states in 129Pr

The 129Nd activities were produced by bombarding 92,94Mo targets with 210 or 255 MeV 40Ca beams. Mass identification was made using the IGISOL technique. A measured β-decay half-life of 7(1)s was assigned to 129Nd. A new low-lying level scheme has been built for 129Pr. The 11/2− state is proposed to be isomeric at 383 keV excitation energy.

First observation of a strongly-coupled band in even-even A ≈ 80 nuclei: 76Kr

A new ΔI = 1 band has been discovered in 76Kr, the first to be observed in an even-even A ≈ 80 nucleus. The rotational band is built upon a K π = 4 (+) state at 2844 keV excitation energy which is interpreted as a strongly-coupled two-quasineutron configuration ( [301] 3 2 − ⊗ [303] 5 2 − ) 4 + at a prolate deformation of π 2 ≈ 0.34.

The structure of28Si above 10 MeV excitation energy II: Assignments of quantum numbers

New assignments of quantum numbers have been obtained for more than 50 levels in28Si between 8953 and 15915 keV excitation energy. They are based on the measurement of γ-ray angular distributions or anisotropies on 29 resonances of the27Al(p, γ) reaction and on the24Mg(a, γ) resonance atEα=3355 keV. A total of 15 high-spin states withI=5–7 has been obtained and the spectrum ofT=1 states has been identified up to 15915 keV excitation energy and a maximum spinI=6.

The nuclear structure of 194Ir studied with the 193Ir(d,p) 194Ir reaction

The nuclear structure of 194Ir was investigated via the 193Ir(d,p) reaction using a 16 MeV deuteron beam. The reaction products were analyzed with a magnetic spectograph and detected with photographic plates. The energy resolutions (FWHM) of the detected particles were typically ≅ 8.9keV. Spectra were recorded at 16 angles. The angular distributions of cross sections were fitted with theoretical curves from DWBA calculations, and the spectroscopic strengths were obtained. Level energies, parities, spectroscopic strengths and possible spin values were determined up to approximately 500 keV excitation energy. The experimental results were compared with the IBFFM and the Nilsson model. It was found that the IBFFM can approximately reproduce the structure of 194Ir, although there is a serious discrepancy with the level observed at 148.7 keV which has a large amount of l = 3 strength. Predictions with the Nilsson model, made for fixed oblate and prolate deformations, did not reproduce the spectroscopic strengths. When spin-parity information for more levels becomes available it may become feasible to improve the description by considering different deformation values, Coriolis mixing and the effects of the mixed target ground state, but at present an unambiguous set of assignments cannot be made.