P. Fallon's research while affiliated with Lawrence Berkeley National Laboratory and other places
What is this page?
This page lists the scientific contributions of an author, who either does not have a ResearchGate profile, or has not yet added these contributions to their profile.
It was automatically created by ResearchGate to create a record of this author's body of work. We create such pages to advance our goal of creating and maintaining the most comprehensive scientific repository possible. In doing so, we process publicly available (personal) data relating to the author as a member of the scientific community.
If you're a ResearchGate member, you can follow this page to keep up with this author's work.
If you are this author, and you don't want us to display this page anymore, please let us know.
It was automatically created by ResearchGate to create a record of this author's body of work. We create such pages to advance our goal of creating and maintaining the most comprehensive scientific repository possible. In doing so, we process publicly available (personal) data relating to the author as a member of the scientific community.
If you're a ResearchGate member, you can follow this page to keep up with this author's work.
If you are this author, and you don't want us to display this page anymore, please let us know.
Publications (878)
The level structure of Al36 has been studied via β decay of Mg36 at the Facility for Rare Isotope Beams (FRIB) and the National Superconducting Cyclotron Laboratory (NSCL). A long-lived isomer in Al36 was identified which decays by β to an excited state of Si36. The ground state and the isomeric state of Al36 were found to populate different energy...
Detailed $\gamma$-ray spectroscopy of the exotic neon isotope $^{28}$Ne has been performed for the first time using the one-neutron removal reaction from $^{29}$Ne on a liquid hydrogen target at 240~MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $^{28}$Ne an...
Excited-state spectroscopy from the first experiment at the Facility for Rare Isotope Beams (FRIB) is reported. A 24(2)−μs isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV γ rays in coincidence with Na32 nuclei. This is the only known microsecond isomer (1 μs≤T1/2<1 ms) in the region. This nucle...
Detailed γ-ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for 28Ne and the negative-parity...
The level structure of Er158 has been studied using the Gammasphere spectrometer via the Cd114(Ca48,4n) reaction at 215 MeV with both thin (self-supporting) and thick (backed) targets. The level scheme has been considerably extended with more than 200 new transitions and six new rotational structures, including two strongly coupled high-K bands. Co...
The deformation properties of the low-lying states in Ge76 have been investigated following a safe-energy Coulomb excitation measurement with the GRETINA tracking array and CHICO2 heavy-ion counter at the ATLAS accelerator facility at Argonne National Laboratory. A comprehensive set of transition and static E2 matrix elements were extracted from th...
Excited-state spectroscopy from the first Facility for Rare Isotope Beams (FRIB) experiment is reported. A 24(2)-$\mu$s isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV $\gamma$ rays in coincidence with $^{32}\textrm{Na}$ nuclei. This is the only known microsecond isomer ($1{\text{ }\mu\text{s}}...
DOI:https://doi.org/10.1103/PhysRevC.107.029902
The Be9(BeF25(5/2+),BeO24)X proton-removal reaction was studied at the NSCL using the S800 spectrometer. The experimental spectroscopic factor for the ground-state to ground-state transition indicates a substantial depletion of the proton d5/2 strength compared to shell-model expectations, similar to the findings of an inverse-kinematics (p,2p) mea...
DOI:https://doi.org/10.1103/PhysRevC.106.059901
New half-lives for exotic isotopes approaching the neutron drip-line in the vicinity of N∼28 for Z=12–15 were measured at the Facility for Rare Isotope Beams (FRIB) with the FRIB decay station initiator. The first experimental results are compared to the latest quasiparticle random phase approximation and shell-model calculations. Overall, the meas...
DOI:https://doi.org/10.1103/PhysRevC.106.049904
DOI:https://doi.org/10.1103/PhysRevC.106.049905
DOI:https://doi.org/10.1103/PhysRevC.106.049902
The collective structure of $^{106}$Cd is elucidated by multi-step Coulomb excitation of a 3.849 MeV/$A$ beam of $^{106}$Cd on a 1.1 mg/cm$^2$ $^{208}$Pb target using GRETINA-CHICO2 at ATLAS. Fourteen $E2$ matrix elements were obtained. The nucleus $^{106}$Cd is a prime example of emergent collectivity that possesses a simple structure: it is free...
![FIG. 2: The experimental level scheme of 25 F from Ref. [28] and the...](publication/363331714/figure/fig2/AS:11431281083314451@1662520469625/The-experimental-level-scheme-of-25-F-from-Ref-28-and-the-results-of-the-PVC-model_Q320.jpg)
The $^{25}$F($5/2^+) (-1p) ^{24}$O reaction was studied at the NSCL using the S800 spectrometer. The experimental spectroscopic factor for the ground-state to ground-state transition indicates a substantial depletion of the proton $d_{5/2}$ strength compared to shell-model expectations. Our result supports the findings reported by Tang \textit{et a...
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/cm² ²⁰⁸Pb 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 sha...
We discuss a phenomenological shell model analysis of the structure of 48,49,50Ca. Based on simple arguments, we propose wavefunctions fit to the available data on spectroscopic factors derived from direct one neutron addition and removal reactions. These empirical wavefunctions are then used to calculate properties of low-lying states in 49,50,51C...
While the phenomenon of one- and two-neutron ground-state halo nuclei is well established, the effects of weak binding on nuclear excitation properties remain largely unexplored. Motivated by this question and by recent data in 40Mg we investigate the coupling of weakly bound (halo) valence neutrons to a core using the known properties of 40Mg to e...
![FIG. 13. Partial level scheme of 29 Ne. The scheme from Ref. [13] has...](publication/358953676/figure/fig4/AS:1170121955520512@1655990222160/Partial-level-scheme-of-29-Ne-The-scheme-from-Ref-13-has-been-extended-to-states_Q320.jpg)
The nucleus Ne29 is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder f7/2 state, which would place Ne29 firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of Ne29 is reported. The states were populated in Ne30(p,pn) and Na30(p,2p) r...
The nucleus $^{29}$Ne is situated at the border of the island of inversion. Despite significant efforts, no bound low-lying intruder $f_{7/2}$-state, which would place $^{29}$Ne firmly inside the island of inversion, has yet been observed. Here, the first investigation of unbound states of $^{29}$Ne is reported. The states were populated in $^{30}\...
Exclusive cross sections for the P43(−1p)Si42 reaction to the lowest 0+ and 2+ states, measured at NSCL with GRETINA and the S800, are interpreted in terms of a two-level mixing (collective) model of oblate and prolate coexisting shapes. Using the formalism developed for deformed nuclei, we calculate the spectroscopic amplitudes and exclusive cross...
While the phenomenon of one- and two-neutron ground-state halo nuclei is well established, the effects of weak binding on nuclear excitation properties remain largely unexplored. Motivated by this question and by recent data in $^{40}$Mg we investigate the coupling of weakly bound (halo) valence neutrons to a core using the known properties of $^{4...
DOI:https://doi.org/10.1103/PhysRevC.104.069902
Compton polarimeters have played an important role in the study of nuclear structure physics, but have often been limited in their applications because of relatively low γ-ray detection efficiency. With the advent of γ-ray tracking detector arrays, which feature nearly 4π solid angle coverage and the ability to identify the location of Compton-scat...
The fusion-evaporation reaction S32+Si28 at 125-MeV beam energy was used to populate excited states in Fe55. Combining the Gammasphere spectrometer with ancillary devices including the Microball CsI(Tl) array and a shell of neutron detectors, a comprehensive level scheme could be derived. The experimental results are compared with theoretical resul...
Exclusive cross sections for the $^{43}$P$(-1p)^{42}$Si reaction to the lowest $0^+$ and $2^+$ states, measured at NSCL with GRETINA and the S800, are interpreted in terms of a two-level mixing (collective) model of oblate and prolate co-existing shapes. Using the formalism developed for deformed nuclei we calculate the spectroscopic amplitudes and...
We have studied the Mg26(t,p)Mg28 reaction. The nucleus Mg28 lies between Mg24 and Mg32, the latter of which is central to the “island of inversion” characterized by low-lying neutron fp-shell configurations. The present results show that the second-excited 0+ state in Mg28 contains large fp-shell occupation for the neutrons. The experiment was per...
The structure of Mg33 was investigated by means of two knockout reactions, one-neutron removal from Mg34 and one-proton removal from Al34. Using comparative analysis of the population of observed excited states in the residual Mg33, the nature of these states can be deciphered. In addition, the long-standing controversy about the parity of the Mg33...
UCGretina, a GEANT4 simulation of the GRETINA gamma-ray tracking array of highly-segmented high-purity germanium detectors is described. We have developed a model of the array, in particular of the Quad Module and the capsules, that gives good agreement between simulated and measured photopeak efficiencies over a broad range of gamma-ray energies a...
UCGretina, a geant4 simulation of the GRETINA gamma-ray tracking array of highly-segmented high-purity germanium detectors is described. We have developed a model of the array, in particular of the Quad Module and the capsules, that gives good agreement between simulated and measured photopeak efficiencies over a broad range of gamma-ray energies a...
High-spin states of the odd-odd nucleus Lu168 were populated in the Sb123(Ca48,3n)Lu168 reaction at a beam energy of 203 MeV and decay γ rays measured using the Gammasphere spectrometer array. The level scheme has been extended from spin 27 to 50 ℏ, and three new rotational bands have been added. A number of interband linking transitions were revea...
Spectroscopic factors to low-lying negative-parity states in Be11 extracted from the B12(d,He3)Be11 proton-removal reaction are interpreted within the rotational model. Earlier predictions of the p-wave proton-removal strengths in the strong-coupling limit of the Nilsson model underestimated the spectroscopic factors to the 3/21− and 5/21− states a...
The structure of $^{33}$Mg was investigated by means of two knockout reactions, one-neutron removal from $^{34}$Mg and one-proton removal from $^{34}$Al. Using comparative analysis of the population of observed excited states in the residual $^{33}$Mg, the nature of these states can be deciphered. In addition, the long-standing controversy about th...
High-spin states in Xe123 were populated in the Se80(Ca48, 5n)Xe123 reaction at a beam energy of 207 MeV. γ-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked...
The excitation energy of deformed intruder states (specifically the 2p2h bandhead) as a function of proton number Z along N=20 is of interest both in terms of better understanding the evolution of nuclear structure between spherical Ca40 and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At the center...
Spectroscopic factors to low-lying negative-parity states in $^{11}$Be extracted from the $^{12}$B($d$,$^3$He)$^{11}$Be proton-removal reaction are interpreted within the rotational model. Earlier predictions of the $p$-wave proton removal strengths in the strong coupling limit of the Nilsson model underestimated the spectroscopic factors to the $3...
The neutron-rich barium nuclei have been the subject of intense interest due to the enhanced octupole correlations they are predicted to exhibit. The observation of enhanced octupole collectivity in Ba144,146 as measured in sub-barrier Coulomb excitation, consistent with static octupole deformation, has further heightened this interest. In the pres...
In a recent experiment, carried out at the Radioactive Isotope Beam Factory/RIKEN, the F25(p,2p)O24 reaction was studied at 270 MeV/A in inverse kinematics. Derived spectroscopic factors suggest that the effective core of F25 significantly differs from a free O24 nucleus. We interpret these results within the particle-rotor model and show that the...
Excited states of neutron-rich iodine isotopes I130–134 above the high-spin isomers have been identified using prompt-delayed γ-ray spectroscopy. The iodine isotopes were produced as fission fragments of fusion-fission and transfer induced fission of Be9(U238,f) at a beam energy of 6.2 MeV/u. The complete (A,Z) identification was obtained using the...
In 1956 A. Kerman explained the observed energy levels of the lowest K = 1/2 and K = 3/2 bands in ¹⁸³ W as resulting from rotational perturbations due to the effects of the Coriolis force. Following from that seminal paper, in this work we consider Kerman’s problem when one of the Nilsson single-particle levels involved is a resonant state. This is...
In a recent experiment, carried out at RIBF/RIKEN, the $^{25}$F$(p,2p)$$^{24}$O reaction was studied at 270 MeV/A in inverse kinematics. Derived spectroscopic factors suggest that the effective core of $^{25}$F significantly differs from a free $^{24}$O nucleus. We interpret these results within the Particle-Rotor Model and show that the experiment...
Background: The Z=50 shell closure, near N=82, is unique in the sense that it is the only shell closure with the spin-orbit partner orbitals, πg9/2 and πg7/2, enclosing the magic gap. The interaction of the proton hole/particle in the above-mentioned orbitals with neutrons in the νh11/2 orbital is an important prerequisite to the understanding of t...
The excitation energy of deformed intruder states (specifically the $2p2h$ bandhead) as a function of proton number $Z$ along $N=20$ is of interest both in terms of better understanding the evolution of nuclear structure between spherical $^{40}$Ca and the Island of Inversion nuclei, and for benchmarking theoretical descriptions in this region. At...
The fusion-evaporation reaction S32+Si28 at 125 MeV beam energy was used to populate high-spin states in the semimagic N=28 nuclei Mn53 and Fe54. With a combination of the Gammasphere spectrometer and ancillary devices including the Microball CsI(Tl) array, extensive high-spin level schemes are derived. They exhibit rotational-like collective struc...
The fusion and transfer induced fission reaction $^{9}$Be($^{238}$U,~f) with 6.2 MeV/u beam energy, using a unique setup consisting of AGATA, VAMOS++ and EXOGAM detectors, was used to populate through the fission process and study the neutron-rich $^{119,121}$In isotopes. This setup enabled the prompt-delayed $\gamma$-ray spectroscopy of isotopes i...
In an experiment performed at Lawrence Berkeley National Laboratory’s 88-inch cyclotron, the isotope Md244 was produced in the Bi209(Ar40,5n) reaction. Decay properties of Md244 were measured at the focal plane of the Berkeley Gas-filled Separator, and the mass number assignment of A=244 was confirmed with the apparatus for the identification of nu...
Spectroscopic strengths for the 18Fg,m(d,p)F19 reactions to members of the ground-state band in F19 are interpreted in the rotational model. The analysis considers two different coupling schemes, namely, the strong and decoupled limits of the particle rotor model to describe the ground and isomeric states of F18, as well as the transitions to the g...
Detailed spectroscopy of the neutron-unbound nucleus F28 has been performed for the first time following proton/neutron removal from Ne29/F29 beams at energies around 230 MeV/nucleon. The invariant-mass spectra were reconstructed for both the F(*)27+n and F(*)26+2n coincidences and revealed a series of well-defined resonances. A near-threshold stat...
Detailed spectroscopy of the neutron-unbound nucleus $^{28}$F has been performed for the first time following proton/neutron removal from $^{29}$Ne/$^{29}$F beams at energies around 230 MeV/nucleon. The invariant-mass spectra were reconstructed for both the $^{27}$F$^{(*)}+n$ and $^{26}$F$^{(*)}+2n$ coincidences and revealed a series of well-define...
The superfluid tunneling model is applied to the calculation of ground-state–to–ground-state α decay in the even-even neutron-deficient Te-Ba nuclei. We show that there is a larger α-particle formation probability in nuclei of this region above Sn100 when compared to analogous nuclei above Pb208. This is consistent with the expected systematic vari...
An experiment involving a heavy-ion induced fusion-evaporation reaction was carried out where high-spin states of 123Xe were populated in the 80Se(48Ca, 5n) 123 Xe reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammmasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the...
The fusion and transfer induced fission reaction 9Be(238U,~f) with 6.2 MeV/u beam energy, using a unique setup consisting of AGATA, VAMOS++ and EXOGAM detectors, was used to populate through the fission process and study the neutron-rich 119,121In isotopes. This setup enabled the prompt-delayed γ-ray spectroscopy of isotopes in the time range of 10...
High spin states in the isotope 194Hg were populated using the 150Nd (48Ca,4n) reaction at a beam energy of 213 MeV. A sequence of dip ole transitions has been observed above 8 MeV excitation energy. Cross-over transitions have also been identified. An interpretation connecting this sequence to a nuclear shape change is attempted. A comparison with...
High spin states in 195Hg, populated using the 150Nd(48 Ca,3n) reaction, were investigated by γ-ray spectroscopic techniques. Two backbendings are observed in the yrast band considered to be caused by the alignment of a pair of i13/2 and p3/2 neutrons respectively. The strong backbending behaviour observed in the negative parity side band is consis...
The neutron-rich Ni isotopes have attracted attention in recent years because of the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in Ni70 following γ-ray tagged one-proton, one-neutron, and two-proton knockout from Cu71, Ni71, and Zn72 rare-isotope beams, respectively. Using var...
The neutron-rich Ni isotopes have attracted attention in recent years due to the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in 70Ni following gamma-ray tagged one-proton, one-neutron, and two-proton knockout from 71Cu, 71Ni, and 72Zn rare-isotope beams, respectively. Using var...
An extensive, model-independent analysis of the nature of triaxial deformation in $^{76}$Ge, a candidate for neutrinoless double-beta ($0\nu\beta\beta$) decay, was carried out following multi-step Coulomb excitation. Shape parameters deduced on the basis of a rotational-invariant sum-rule analysis provided considerable insight into the underlying c...
An extensive, model-independent analysis of the nature of triaxial deformation in Ge76, a candidate for neutrinoless double-beta (0νββ) decay, was carried out following multistep Coulomb excitation. Shape parameters deduced on the basis of a rotational-invariant sum-rule analysis provided considerable insight into the underlying collectivity of the...
β− decay of Tz=+112 nuclei Al37 and Si39 was studied to obtain information about excited states in the daughter and granddaughter nuclei. New information on excited states has been obtained for P37,39, whereas level schemes for Si37 and S37,39 were confirmed and expanded on as compared to the most recent investigations. For the nuclei studied, the...
The neutron-rich $^{122-131}$Sb isotopes were produced as fission fragments in the reaction $^{9}$Be($^{238}$U,~f) with 6.2 MeV/u beam energy. An unique setup, consisting of AGATA, VAMOS++ and EXOGAM detectors, was used which enabled the prompt-delayed gamma-ray ($\gamma$) spectroscopy of fission fragments in the time range of 100 ns - 200 $\mu$s....
Background: Levels fulfilling the seniority scheme and relevant isomers are commonly observed features in semimagic nuclei; for example, in Sn isotopes (Z=50). Seniority isomers in Sn, with dominantly pure neutron configurations, directly probe the underlying neutron-neutron (νν) interaction. Furthermore, an addition of a valence proton particle or...
The superfluid tunneling model is applied to the calculation of half-lives of the observed α decays in N=84 isotones. Results of our calculations are compared to experimental data on the ground-state α decays along the isotonic chain from Nd144 to Re159. Good agreement is found. The α decays of the known high-spin isomers in Lu155, Hf156, Ta157, an...
One of the most exotic light neutron-rich nuclei currently accessible for experimental study is Mg40, which lies at the intersection of the nucleon magic number N=28 and the neutron drip line. Low-lying excited states of Mg40 have been studied for the first time following a one-proton removal reaction from Al41, performed at the Radioactive Isotope...
Low-lying states of neutron-rich Ne32 were populated by means of one- and two-proton knockout reactions at the RIKEN Radioactive Isotope Beam Factory. A new transition is observed at 1410(15) keV and assigned to the 41+→21+ decay. With this energy the R4/2 ratio is calculated to be 2.99(6), lying close to the rigid rotor limit and suggests a high d...
Purpose: Benchmark the reproducibility of the experimental observables, like the excitation energies (EX) and
the reduced electric-quadrupole transition probabilities [B(E2)], with the results obtained from shell-model
interactions for neutron-rich Sn and Sb isotopes with N < 82. Study the sensitivity of the aforementioned
experimental observables...
An experiment was performed at Lawrence Berkeley National Laboratory’s 88-in. Cyclotron to determine the mass number of a superheavy element. The measurement resulted in the observation of two α-decay chains, produced via the Am243(Ca48,xn)291−xMc reaction, that were separated by mass-to-charge ratio (A/q) and identified by the combined BGS+FIONA a...
The energy levels and γ-ray decay scheme of the positive-parity states in the Tz=12 nucleus As67 have been studied by using the Ca40(Ar36,2αp)As67 reaction at a beam energy of 145 MeV. Two new band structures have been identified which can be connected to the previously known levels. The results for these bands are compared with configuration-depen...
DOI:https://doi.org/10.1103/PhysRevC.97.049902
A model-independent technique was used to determine the γ-ray strength function (γSF) of Fe56 down to γ-ray energies less than 1 MeV for the first time with GRETINA using the (p,p′) reaction at 16 MeV. No difference was observed in the energy dependence of the γSF built on 2+ and 4+ final states, supporting the Brink hypothesis. In addition, angula...
High-spin states in 124 Cs were populated in the 64 Ni(64 Ni, p3n) reaction and the Gammasphere detector array was used to measure γ-ray coincidences. Both, positive and negative parity bands, including bands with chiral configurations, have been extended to higher spin, where a shape change has been observed. The configurations of the bands before...
A model-independent technique was used to determine the $\gamma$-ray Strength Function ($\gamma$SF) of $^{56}$Fe down to $\gamma$-ray energies less than 1 MeV for the first time with GRETINA using the $(p,p')$ reaction at 16 MeV. No difference was observed in the energy dependence of the $\gamma$SF built on $2^{+}$ and $4^{+}$ final states, support...
Spectroscopic factors, extracted from one-neutron knockout and Coulomb dissociation reactions, for transitions from the ground state of Mg33 to the ground-state rotational band in Mg32, and from Mg32 to low-lying negative-parity states in Mg31, are interpreted within the rotational model. Associating the ground state of Mg33 and the negative-parity...
The structure of ⁷¹Zn was investigated by one-neutron transfer and heavy-ion induced complex (deep-inelastic) reactions using the GRETINA-CHICO2 and the Gammasphere setups, respectively. The observed inversion between the 9/2⁺ and 1/2⁻ states is explained in terms of the role of neutron pairing correlations. Non-collective sequences of levels were...
Recent results from RIKEN/RIBF on the low-lying level structure of 29F are interpreted within the Particle-Rotor Model. We show that the experimental data can be understood in the Rotation-aligned Coupling Scheme, with the 5/2+ ground state as the bandhead of a decoupled band. In this picture, the energy of the observed 1/2+1 state correlates stron...
