This year is the 100th anniversary of the discovery of the Compton effect marked by A. H. Compton’s 1923 Physical Review article. On this occasion, we reflect on the effect’s impact on Nuclear ...Physics and celebrate the event a century ago and the eminent scientist who made the discovery. Much of the historical comments rely on the article by R. H. Stuewer. A recent Physics Today article presents a historical perspective of Compton’s work and provides more details. The various applications of the Compton effect and its “derivatives” (e.g. inverse Compton scattering) impact many areas of Physics and Chemistry. Here, this short article is restricted to examples taken from the authors' surroundings: the focus is on nuclear-structure experiments with γ-spectroscopic methods and nuclear cross-section measurements relevant for astrophysics.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
A novel pathway for the formation of multiparticle-multihole excited states in rare isotopes is reported from highly energy- and momentum-dissipative inelastic-scattering events measured in reactions ...of an intermediate-energy beam of ^{38}Ca on a Be target. The negative-parity, complex-structure final states in ^{38}Ca are observed following the in-beam γ-ray spectroscopy of events in the ^{9}Be(^{38}Ca,^{38}Ca+γ)X reaction in which the scattered projectile loses longitudinal momentum of order Δp_{||}=700 MeV/c. The characteristics of the observed final states are discussed and found to be consistent with the formation of excited states involving the rearrangement of multiple nucleons in a single, highly energetic projectile-target collision. Unlike the far-less-dissipative, surface-grazing reactions usually exploited for the in-beam γ-ray spectroscopy of rare isotopes, these more energetic collisions appear to offer a practical pathway to nuclear-structure studies of more complex multiparticle configurations in rare isotopes-final states conventionally thought to be out of reach with high-luminosity fast-beam-induced reactions.
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We have performed a detailed γ-ray spectroscopy study of the nucleus, 49Mn, using the GRETINA tracking array and FMA recoil separator. With this powerful new setup, low-spin excited states, which are ...most relevant for astrophysical processes, have been identified for the first time, including four proton-unbound levels, corresponding to key astrophysical resonances in the 48Cr(p,γ)49Mn reaction. Of these four levels, two were found to dominate the 48Cr(p,γ)49Mn reaction for temperatures, T = 0.2 − 1.4 GK, and uncertainties in the rate have been reduced by more than 3 orders of magnitude. Specifically, γ decays were observed from 1/2+ and 3/2− excited states at Ex = 2570.9(26) keV and 2595.8(21) keV, corresponding to an ℓ = 0 and ℓ = 1 resonance in the 48Cr + p system at Er = 482.9(84) keV and 507.9(83) keV, respectively. Present simulations of Type-I X-ray burst nucleosynthesis indicate that the newly defined 48Cr(p,γ) reaction rate is sufficiently fast to drive the flow of material towards higher masses in such environments. Consequently, despite the relatively long half life of 48Cr, we now do not expect a strong waiting point in the rp process at A = 48.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The collective structure of 106Cd is elucidated by multi-step Coulomb excitation of a 3.849 MeV/A beam of 106Cd on a 1.1 mg/cm2208Pb target using GRETINA-CHICO2 at ATLAS. Fourteen E2 matrix elements ...were obtained. The nucleus 106Cd is a prime example of emergent collectivity that possesses a simple structure: it is free of complexity caused by shape coexistence and has a small, but collectively active number of valence nucleons. This work follows in a long and currently active quest to answer the fundamental question of the origin of nuclear collectivity and deformation, notably in the cadmium isotopes. The results are discussed in terms of phenomenological models, the shell model, and Kumar-Cline sums of E2 matrix elements. The 〈02+||E2||21+〉 matrix element is determined for the first time, providing a total, converged measure of the electric quadrupole strength, 〈Q2〉, of the first-excited 21+ level relative to the 01+ ground state, which does not show an increase as expected of harmonic and anharmonic vibrations. Strong evidence for triaxial shapes in weakly collective nuclei is indicated; collective vibrations are excluded. This is contrary to the only other cadmium result of this kind in 114Cd by C. Fahlander et al. (1988) 38, which is complicated by low-lying shape coexistence near midshell.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report on the first in-beam γ-ray spectroscopy of the proton-dripline nucleus 40Sc using two-nucleon pickup onto an intermediate-energy rare-isotope beam of 38Ca. The 9Be(38Ca,40Sc+γ)X reaction at ...60.9 MeV/nucleon mid-target energy selectively populates states in 40Sc for which the transferred proton and neutron couple to high orbital angular momentum. In turn, due to angular-momentum selection rules in proton emission and the nuclear structure and energetics of 39Ca, such states in 40Sc then exhibit γ-decay branches although they are well above the proton separation energy. This work uniquely complements results from particle spectroscopy following charge-exchange reactions on 40Ca as well as 40Ti EC/β+ decay which both display very different selectivities. The population and γ-ray decay of the previously known first (5−) state at 892 keV and the observation of a new level at 2744 keV are discussed in comparison to the mirror nucleus and shell-model calculations. On the experimental side, this work shows that high-resolution in-beam γ-ray spectroscopy is possible with new generation Ge arrays for reactions induced by rare-isotope beams on the level of a few μb of cross section.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Spectroscopy of 187Tl: shape coexistence Guo, C. Y.; Zhang, W. Q.; Huang, H. ...
The European physical journal. A, Hadrons and nuclei,
08/2024, Volume:
60, Issue:
8
Journal Article
Peer reviewed
The prompt and delayed
γ
-ray spectra of
187
Tl was studied via the
142
Nd(
50
Cr, 3
p
2
n
)
187
Tl fusion-evaporation reaction at a beam energy of 255 MeV. An enhanced level scheme of
187
Tl was ...established. The collective bands with one-quasiparticle configurations from the
2
f
7
/
2
,
1
h
9
/
2
,
1
h
11
/
2
and
1
i
13
/
2
orbitals and high-lying structures with possible three-quasiparticle configurations are investigated in terms of the tilted axis cranking covariant density functional theory. At low excitation energy, the rotational bands with one-quasiparticle configurations reflect coexistence of three shapes: prolate, triaxial, and oblate. The possible shapes of two microsecond isomers at high excitation energy are proposed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The decay of the 13/2+ isomeric state in 183Hg was observed for the first time following the a decay of the 13/2+ isomer in 187Pb produced in the 142Nd(50Cr, 2p3n) reaction. Using $\alpha - \gamma$ ...delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) μs. This isomer is proposed to deexcite by an unobserved low-energy M2 transition to the known 9/2- member of a strongly prolate-deformed 7/2-514 band, followed by a 105-keV M1 transition to the bandhead. A lower limit of B(M2) >= 0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2+ isomer in 181Hg, suggesting both are cases of shape isomers. The B(M2) systematics of neutron transitions across the nuclear chart is discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Prompt and delayed γ-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled ...Analyzer. A new 5.15(15)-μs isomeric state at only 308 keV above the spherical 3/2− ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2−514 Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2−)→3/2gs− transition with a deduced B(E2)=5.6(2)×10−4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous α-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The observation of γ rays from the decay of 44Ti in the remnants of core-collapse supernovae (CCSNe) provides crucial information regarding the nucleosynthesis occurring in these events, as 44Ti ...production is sensitive to CCSNe conditions. The final abundance of 44Ti is also sensitive to specific nuclear input parameters, one of which is the 57Ni(p,γ)58Cu reaction rate. A precise rate for 57Ni(p,γ)58Cu is thus critical if 44Ti production is to be an effective probe into CCSNe. To experimentally constrain the 57Ni(p,γ)58Cu rate, the structure properties of 58Cu were measured via the 58Ni(3He,t)58Cu*(γ) reaction using GODDESS (GRETINA ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory’s ATLAS facility. Details of the experiment, ongoing analysis, and plans are presented.
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