Shape coexistence in Hg-178

Lifetime measurements of excited states in Hg-178 have been performed using the Rh-103(Kr-78, p2n) reaction at a beam energy of 354 MeV. The recoil-decay tagging (RDT) technique was applied to select the Hg-178 nuclei and associate the prompt gamma rays with the correlated characteristic ground-state alpha decay. Lifetimes of the four lowest yrast states of Hg-178 have been determined using the recoil distance Doppler-shift (RDDS) method. The experimental data are compared to theoretical predictions with focus on shape coexistence. The results confirm the shift of the deformed prolate structures to higher lying states but also indicate their increasing deformation with decreasing neutron nu…

In-beam spectroscopic study of Cf244

The ground-state rotational band of the neutron-deficient californium (Z = 98) isotope 244Cf was identified for the first time and measured up to a tentative spin and parity of I I-pi = 20(+). The observation of the rotational band indicates that the nucleus is deformed. The kinematic and dynamic moments of inertia were deduced from the measured gamma-ray transition energies. The behavior of the dynamic moment of inertia revealed an up-bend due to a possible alignment of coupled nucleons in high-j orbitals starting at a rotational frequency of about (h) over bar (omega) = 0.20 MeV. The results were compared with the systematic behavior of the even-even N = 146 isotones as well as with avail…

Towards saturation of the electron-capture delayed fission probability : The new isotopes 240Es and 236Bk

The new neutron-deficient nuclei 240Es and 236Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from 240Es produced in the fusion–evaporation reaction 209Bi(34S,3n)240Es. Half-lives of 6(2) sand 22+13−6swere obtained for 240Es and 236Bk, respectively. Two groups of αparticles with energies Eα=8.19(3) MeVand 8.09(3) MeVwere unambiguously assigned to 240Es. Electron-capture delayed fission branches with probabilities of 0.16(6)and 0.04(2)were measured for 240Es and 236Bk, respectively. These new data show a continuation of the exponential increase of ECDF probabilities in more neutron-deficient isotopes. peerReviewed

In-beam spectroscopy with intense ion beams: Evidence for a rotational structure in246Fm

The rotational structure of ${}^{246}$Fm has been investigated using in-beam $\ensuremath{\gamma}$-ray spectroscopic techniques. The experiment was performed using the JUROGAMII germanium detector array coupled to the gas-filled recoil ion transport unit (RITU) and the gamma recoil electron alpha tagging (GREAT) focal plane detection system. Nuclei of ${}^{246}$Fm were produced using a 186 MeV beam of ${}^{40}$Ar impinging on a ${}^{208}$Pb target. The JUROGAMII array was fully instrumented with Tracking Numerical Treatment 2 Dubna (TNT2D) digital acquisition cards. The use of digital electronics and a rotating target allowed for unprecedented beam intensities of up to 71 particle-nanoamper…

Prompt and delayed spectroscopy of 203At : Observation of a shears band and a 29/2+ isomeric state

Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of 203 At ( N = 118 ) significantly. We have observed an isomeric [ τ = 14.1 ( 3 ) μ s ] state with a spin and parity of 29 / 2 + . The isomeric state is suggested to originate from the π ( h 9 / 2 ) ⊗ ∣ ∣ 202 Po ; 11 − ⟩ coupling, and it is depopulated through 286 keV E 2 and 366 keV E 3 transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism. peerReviewed

Confirmation of the new isotope Pb178

The extremely neutron-deficient isotope $^{178}\mathrm{Pb}$ has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the $\ensuremath{\alpha}$ decay of $^{178}\mathrm{Pb}$ and its $\ensuremath{\alpha}$-decay chain through $\ensuremath{\alpha}\text{\ensuremath{-}}\ensuremath{\alpha}$ correlations. The $\ensuremath{\alpha}$ decay was measured to have an energy and half-life of ${E}_{\ensuremath{\alpha}}$= 7610(30) keV and ${t}_{1/2}=0.{21}_{\ensuremath{-}0.08}^{+0.21}$ ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The $\ensuremath{\alpha}$-decay…

Experimental study of isomeric intruder 12+ states in At197,203

A newly observed isomeric intruder ${\textonehalf{}}^{+}$ state $[{T}_{\textonehalf{}}=3.5(6)\phantom{\rule{0.16em}{0ex}}\mathrm{ms}]$ is identified in $^{203}\mathrm{At}$ using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of $E3$ and mixed $M1/E2$ transitions to the ${9/2}^{\ensuremath{-}}$ ground state, and it is suggested to originate from the $\ensuremath{\pi}{({s}_{\textonehalf{}})}^{\ensuremath{-}1}$ configuration. In addition, the structures above the ${\textonehalf{}}^{+}$ state in $^{203}\mathrm{At}$ and $^{197}\mathrm{At}$ are studied using in-beam $\ensuremath{\gamma}$-ray spectroscopy, recoil-decay tagging, and recoi…

Recoil-decay tagging spectroscopy of74162W88

Excited states in the highly neutron-deficient nucleus W-162 have been investigated via the Mo-92(Kr-78, 2 alpha) W-162 reaction. Prompt gamma rays were detected by the JUROGAM II high-purity germa ...

First observation of excited states of173Hg

The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of gamma rays decaying from excited states are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighbouring neutron-deficient Hg nuclei. In addition to the gamma-ray spectroscopy, the alpha decay of this nucleus has been measured yielding superior precision to earlier measurements.

Prompt gamma ray-spectroscopy of N = 50 fission fragments

Excited states in the nuclei 83 As and 84,86 Se have been studied via prompt -ray spectroscopy. The nuclei were produced by the proton-induced fission of a 238 U target, at the accelerator of the University of Jyvaskyla. The JUROGAM-II array was used to detect prompt -rays and a triple- coincidence analysis performed. A comparison of the N = 50 nuclei with shell-model calculations reproduces the low-lying states in 83 As and 84 Se well. The inclusion of particle-hole excitations is necessary to correctly describe the states above ∼ 3.5 MeV.

Reduced transition probabilities along the yrast line in W-166

WOS: 000406755100001

Confirmation of the new isotope 178Pb

The extremely neutron-deficient isotope 178Pb has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the α decay of 178Pb and its α-decay chain through α-α correlations. The α decay was measured to have an energy and half-life of Eα= 7610(30) keV and t1/2 = 0.21+0.21 −0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The α-decay reduced width and hindrance factor for 178Pb were deduced and correspond to an unhindered l = 0 transition. In addition, the mass excess of 178Pb and the α-decay Q value were calculated from the experimental results…

Lifetime measurement of the first excited 2+ state in 112Te

The lifetime of the 2+ → 0+ g.s. transition in the neutron-deficicient nucleus 112Te has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift technique. The deduced value for the reduced transition probability is B(E2 :0+ g.s. → 2+) = 0.46 ± 0.04 e2b2, indicating that there is no unexpected enhancement of the B(E2 :0+ g.s. → 2+) values in Te isotopes below the midshell. The result is compared to and discussed in the framework of large-scale shell-model calculations. peerReviewed

Identification of the Jπ = 1− state in 218Ra populated via α decay of 222Th

The α decay of 222Th populating the low-lying J π = 3− state, and also a proposed 1− state, in 218Ra has been observed. The observations suggest an excitation energy of 853 keV for the 1− state, which is 60 keV above the 3− state. The hindrance factors of these α decays give a possible boundary to the region of ground-state octupole deformation in the light-actinide nuclei. The relative positions of the J π = 1− and 3− states suggest they are produced by an octupole-vibrational mechanism, as opposed to α clustering or rotations of a reflection-asymmetric octupole-deformed shape. peerReviewed

Promptγ-ray spectroscopy of the neutron-rich124Cd

Prompt γ -ray spectroscopy of neutron-rich cadmium isotopes has been performed. The nuclei of interest have been populated via a 25-MeV, proton-induced fission of the 238 U thick target and prompt γ -rays measured using the multi-detector HPGe array JUROGAM II. New high-spin decays have been observed and placed in the level scheme using triple coincidence gates. The experimental results are compared to shell-model calculations and show good agreement.

Spectroscopy of 161Hf from low to high spin

Excited states in the neutron-deficient nucleus 161 72Hf89 have been populated using the 118Sn(48Ti,5n) 161Hf and 110Pd(56Fe,5n) 161Hf fusion-evaporation reactions at 240 and 270 MeV, respectively. The level scheme for 161Hf has been extended with the observation of new band structures and an I π = (13/2+) isomeric state with a half-life of 4.8(2) μs has been identified. The decay path from this isomer to the (7/2−) ground state is established. The yrast band, based on the (13/2+) isomeric state, is extended up to (73/2+) and side band structures are identified up to (69/2−) and (55/2−). Quasiparticle assignments for these rotational structures are made on the basis of their alignment prope…

Reduced transition probabilities along the yrast line in 166W

Lifetimes of excited states in the yrast band of the neutron-deficient nuclide 166W have been measured utilizing the DPUNS plunger device at the target position of the JUROGAM II γ -ray spectrometer in conjunction with the RITU gas-filled separator and the GREAT focal-plane spectrometer. Excited states in 166W were populated in the 92Mo(78Kr,4p) reaction at a bombarding energy of 380 MeV. The measurements reveal a low value for the ratio of reduced transitions probabilities for the lowest-lying transitions B(E2; 4+ → 2+)/B(E2; 2+ → 0+) = 0.33(5), compared with the expected ratio for an axially deformed rotor (B4/2 = 1.43). peerReviewed

Experimental investigation of the 0⁺₂ band in ¹⁵⁴Sm as a β-vibrational band

First prompt in-beam gamma-ray spectroscopy of a superheavy element: the 256Rf

Using state-of-the-art γ-ray spectroscopic techniques, the first rotational band of a superheavy element, extending up to a spin of 20 ¯h, was discovered in the nucleus 256Rf. To perform such an experiment at the limits of the present instrumentation, several developments were needed. The most important of these developments was of an intense isotopically enriched 50Ti beam using the MIVOC method. The experimental set-up and subsequent analysis allowed the 256Rf ground-state band to be revealed. The rotational properties of the band are discussed and compared with neighboring transfermium nuclei through the study of their moments of inertia. These data suggest that there is no evidence of a…

Fine structure in the α decay of 156Lu and 158Ta

Fine structure in the α decay of high-spin states in 156Lu and 158Ta has been identified by means of αγ - coincidence analysis. One new α decay from 156Lu and two from 158Ta were identified, one of which was found to populate a previously unknown state in 154Lu. The hindrance-factor systematics from all four odd-odd, N = 85 nuclei with known α-decaying, πh11/2 coupled states were reviewed and are discussed. These proved consistent with the previously assigned (πh11/2νh9/2 )10+ configuration of the α-decaying state in 156Lu, which differs from the (πh11/2ν f7/2 )9+ assignments in the other three nuclei. peerReviewed

Towards saturation of the electron-capture delayed fission probability: The new isotopes $^{240}Es$ and $^{236}Bk$

Abstract The new neutron-deficient nuclei 240 Es and 236 Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from 240 Es produced in the fusion–evaporation reaction 209 Bi( 34 S,3n) 240 Es. Half-lives of 6 ( 2 ) s and 22 − 6 + 13 s were obtained for 240 Es and 236 Bk, respectively. Two groups of α particles with energies E α = 8.19 ( 3 ) MeV and 8.09 ( 3 ) MeV were unambiguously assigned to 240 Es. Electron-capture delayed fission branches with probabilities of 0.16 ( 6 ) and 0.04 ( 2 ) were measured for 240 Es and 236 Bk, respectively. These new data show a continuation of the exponential increase of ECDF probabilitie…

Identification of a dipole band above the Iπ = 31/2- isomeric state in 189Pb

A dipole band of six transitions built upon a firmly established I π = 31/2− isomeric state has been identified in 189Pb using recoil-isomer tagging. This is the lightest odd-mass Pb nucleus in which a dipole band is known. The dipole nature of the new transitions has been confirmed through angular-intensity arguments. The evolution of the excitation energy and the aligned-angular momentum of the states in the new dipole band are compared with those of dipole bands in heavier, odd-mass lead isotopes. This comparison suggests that the new band in 189Pb is based upon a π[s−2 1/2h9/2i13/2]11− ⊗ ν[i −1 13/2+ ]13/2+ configuration. However, the increased aligned-angular momentum in 189Pb may sugg…

Experimental study of isomeric intruder ½+ states 197,203At

A newly observed isomeric intruder ½ + state [ T ½ = 3.5 ( 6 ) ms ] is identified in 203 At using a gas-filled recoil separator and fusion-evaporation reactions. The isomer is depopulated through a cascade of E 3 and mixed M 1 / E 2 transitions to the 9 / 2 − ground state, and it is suggested to originate from the π ( s ½ ) − 1 configuration. In addition, the structures above the ½ + state in 203 At and 197 At are studied using in-beam γ -ray spectroscopy, recoil-decay tagging, and recoil-isomer decay tagging methods. The ½ + state is fed from 3 / 2 + and 5 / 2 + states, and the origin of these states are discussed. peerReviewed

Characterizing the atomic mass surface beyond the proton drip line viaα-decay measurements of theπs1/2ground state of165Re and theπh11/2isomer in161Ta

The α-decay chains originating from the πs1/2 and πh11/2 states in 173Au have been investigated following fusion-evaporation reactions. Four generations of α radioactivities have been correlated with 173Aum leading to a measurement of the α decay of 161Tam. It has been found that the known α decay of 161Ta, which was previously associated with the decay of the ground state, is in fact the decay of an isomeric state. This work also reports on the first observation of prompt γ rays feeding the ground state of 173Au. This prompt γ radiation was used to aid the study of the α-decay chain originating from the πs1/2 state in 173Au. Three generations of α decays have been correlated with this stat…

Identification of a 6.6μs isomeric state in 175Ir

An experiment has been performed to study excited states in the neutron-deficient nucleus 175Ir via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyväskylä. By using isomer tagging, an isomeric state with a half-life of 6.58(15) μs has been observed in 175Ir for the first time. It has been established that the isomer decays via a 45.2 (E1)–26.1 (M1) keV cascade to new states below the previously reported ground state in 175Ir with Iπ = (5/2−). We now reassign this (5/2−) state to the isomeric state discovered in this study. peerReviewed

Fine structure in the α decay of high-spin isomers in 155Lu and 156Hf

Fine structure in the α decay of high-spin isomers in 155Lu(25/2−) and 156Hf (8+) has been studied for the first time using αγ -coincidence analysis. Three new α decays from 155Lu(25/2−) and two from 156Hf (8+) have been identified, populating seniority s > 1 states in the N = 82 nuclei 151Tm and 152Yb, respectively. The reduced hindrance factors of the α decays support the previous configuration assignments of the populated states. This is the first observation of states with excitation energy greater than 1.5 MeV being populated following α decay in nuclei outside of the 208Pb region. peerReviewed

Detailed spectroscopy of Bi195

An experiment focused on the study of shape coexistence and new high-spin structures in $^{195}\mathrm{Bi}$ has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the $13/{2}^{+}$ isomeric state was extended up to ${I}^{\ensuremath{\pi}}=(49/{2}^{+})$ and an energy of 5706 keV. The ${I}^{\ensuremath{\pi}}=31/{2}^{+}$ member of the $\ensuremath{\pi}{i}_{13/2}$ band was also found to feed a new long-lived isomeric state with an excitation …

Determination of the B(E3, 0+ → 3−)-excitation strength in octupole-correlated nuclei near A ≈224 by the means of Coulomb excitation at REX-ISOLDE

The IS475 collaboration conducted Coulomb-excitation experiments with postaccelerated radioactive 220Rn and 224Ra beams at the REX-ISOLDE facility. The beam particles (Ebeam ≈ 2.83 MeV/u) were Coulomb excited using 60Ni, 114Cd, and 120Sn scattering targets. De-excitation γ-rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured γ-ray yields. The extracted 3−||Ê3||0+ matrix element allows for the conclusion that, while 220Rn represents an octupole vibrational system, 224Ra has already substantial octupole correlations i…

Decay of a 19− isomeric state in Lu156

A multiparticle spin-trap isomeric state having a half-life of 179(4) ns and lying 2601 keV above the yrast 10(+) state in Lu-156 has been discovered. The Lu-156 nuclei were produced by bombarding ...

First prompt in-beam γ-ray spectroscopy of a superheavy element: the256Rf

Using state-of-the-art γ-ray spectroscopic techniques, the first rotational band of a superheavy element, extending up to a spin of 20 , was discovered in the nucleus 256Rf. To perform such an experiment at the limits of the present instrumentation, several developments were needed. The most important of these developments was of an intense isotopically enriched 50Ti beam using the MIVOC method. The experimental set-up and subsequent analysis allowed the 256Rf ground-state band to be revealed. The rotational properties of the band are discussed and compared with neighboring transfermium nuclei through the study of their moments of inertia. These data suggest that there is no evidence of a s…

Lifetime measurement of the first excited2+state inTe112

The lifetime of the 2(+) --> 0(g.s.)(+) transition in the neutron-deficicient nucleus Te-112 has been measured for the first time using the DPUNS plunger and the recoil distance Doppler shift te ...

α decay of the πh11/2 isomer in Ir164

The α -decay branch of the πh 11 / 2 isomer in 164 Ir has been identified using the GREAT spectrometer. The 164 Ir nuclei were produced using the 92 Mo( 78 Kr ,p 5 n ) 164 Ir reaction and separated in flight using the recoil ion transport unit (RITU) gas-filled separator. The measured α -decay energy of 6880 ± 10 keV allowed the excitation of the πh 11 / 2 state in 160 Re to be deduced as 166 ± 14 keV. The half-life of 164 Ir was measured with improved precision to be 70 ± 10 μ sandan α -decay branching ratio of 4 ± 2% was determined. Improved half-life and branching ratio measurements were also obtained for 165 Ir, but no evidence was found for the ground-state decays of either 164 Ir or 1…

Excited states in the proton-unbound nuclide Ta-158

Excited states in the neutron-deficient odd-odd proton-unbound nuclide $^{158}\mathrm{Ta}$ have been investigated in two separate experiments. In the first experiment, $^{166}\mathrm{Ir}$ nuclei were produced in the reactions of 380 MeV $^{78}\mathrm{Kr}$ ions with an isotopically enriched $^{92}\mathrm{Mo}$ target. The $\ensuremath{\alpha}$-decay chain of the ${9}^{+}$ state in $^{166}\mathrm{Ir}$ was analyzed. Fine structure in the $\ensuremath{\alpha}$ decay of the ${9}^{+}$ state in $^{162}\mathrm{Re}$ established a 66 keV difference in excitation energy between the lowest-lying ${9}^{+}$ and ${10}^{+}$ states in $^{158}\mathrm{Ta}$. Higher-lying states in $^{158}\mathrm{Ta}$ were popul…

Decay spectroscopy of 179 82 Pb 97 and evidence for a 9/2− intruder state in 179 81 Tl 98

The very neutron-deficient isobars 179Pb and 179Tl have been produced using the fusion-evaporation reactions 104Pd(78Kr,xpyn), where x≤1 and y≥2. The gas-filled separator RITU was employed to transport and separate the recoiling nuclei of interest from the scattered beam and unwanted products. The GREAT spectrometer was used to study the decay properties through α−α and α−γ correlations, which has allowed the ground state of 179Pb to be assigned as Iπ=9/2−. The decay of 179Pb was measured to have an α-particle energy and half-life of Eα=7348(5)keV and t1/2=2.7(2) ms, respectively. A search for a νi13/2 state in 179Pb was performed, but only a limit of excitation energy and half-life was obt…

Recoil-decay tagging spectroscopy of 162 74 W 88

Excited states in the highly neutron-deficient nucleus 162W have been investigated via the 92Mo(78Kr, 2α) 162W reaction. Prompt γ rays were detected by the JUROGAM II high-purity germanium detector array and the recoiling fusion-evaporation products were separated by the recoil ion transport unit (RITU) gas-filled recoil separator and identified with the gamma recoil electron alpha tagging (GREAT) spectrometer at the focal plane of RITU. γ rays from 162W were identified uniquely using mother-daughter and mother-daughter-granddaughter α-decay correlations. The observation of a rotational-like ground-state band is interpreted within the framework of total Routhian surface (TRS) calculations, …

Decay spectroscopy of Pb97182179 and evidence for a 9/2− intruder state in Tl98181179

The very neutron-deficient isobars Pb-179 and Tl-179 have been produced using the fusion-evaporation reactions Pd-104(Kr-78,xpyn), where x = 2. The gas-filled separator RITU was employed to transpo ...

Excited states in the proton-unbound nuclide 158Ta

Excited states in the neutron-deficient odd-odd proton-unbound nuclide 158Ta have been investigated in two separate experiments. In the first experiment, 166Ir nuclei were produced in the reactions of 380 MeV 78Kr ions with an isotopically enriched 92Mo target. The α-decay chain of the 9+ state in 166Ir was analyzed. Fine structure in the α decay of the 9+ state in 162Re established a 66 keV difference in excitation energy between the lowest-lying 9+ and 10+ states in 158Ta. Higher-lying states in 158Ta were populated in the reactions of 255 MeV 58Ni ions with an isotopically enriched 102Pd target. Gamma-ray decay paths that populate, depopulate, and bypass a 19− isomeric state have been id…

Fine structure in the α decay of high-spin isomers in Lu155 and Hf156

Fine structure in the a decay of high-spin isomers in Lu-155( 25/2(-)) and Hf-156(8(+))has been studied for the first time using alpha gamma- coincidence analysis. Three new a decays from Lu-155(25 ...

Lifetime measurements in 166Re : Collective versus magnetic rotation

Lifetimes of excited states in the neutron-deficient odd-odd nucleus 166Re have been measured for the first time using the recoil distance Doppler-shift method. The measured lifetime for the (8−) state; τ = 480 (80) ps, enabled an assessment of the multipolarities of the γ rays depopulating this state. Information on electromagnetic transition strengths were deduced for the γ -ray transitions from the (9−), (10−), and (11−) states, and in the case of the (10−) and (11−) states limits on the B(M1) and B(E2) strengths were estimated. The results are compared with total Routhian surface predictions and semiclassical calculations. Tilted-axis cranking calculations based on a relativistic mean-f…

Experimental investigation of the 02+ band in Sm154 as a β-vibrational band

Abstract A study of Sm 154 through γ -ray and internal conversion electron coincidence measurements was performed using the Silicon And GErmanium spectrometer (SAGE). An upper limit for the ρ 2 ( E 0 ; 2 2 + → 2 1 + ) and measurement of the ρ 2 ( E 0 ; 4 2 + → 4 1 + ) monopole transitions strengths were determined. The extracted transition strength for each is significantly lower than that predicted by either the Bohr and Mottelson β -vibration description or the interacting boson model. Hence, the long standing interpretation of these states as a collective band built on the 0 2 + state, which is conventionally assigned as a Bohr and Mottelson β vibration is questionable.

Production cross section and decay study of Es243 and Md249

In the study of the odd-$Z$, even-$N$ nuclei $^{243}$Es and $^{249}$Md, performed at the University of Jyv\"askyl\"a, the fusion-evaporation reactions $^{197}$Au($^{48}$Ca,2$n$)$^{243}$Es and $^{203}$Tl($^{48}$Ca,2$n$)$^{249}$Md have been used for the first time. Fusion-evaporation residues were selected and detected using the RITU gas-filled separator coupled with the focal-plane spectrometer GREAT. For $^{243}$Es, the recoil decay correlation analysis yielded a half-life of $24 \pm 3$s, and a maximum production cross section of $37 \pm 10$ nb. In the same way, a half-life of $26 \pm 1$ s, an $\alpha$ branching ratio of 75 $\pm$ 5%, and a maximum production cross section of 300 $\pm$ 80 nb…

Investigation into the Effects of Deformation on Proton Emission Rates via Lifetime Measurements

Spectroscopy at the two-proton drip line: Excited states in 158W

Abstract Excited states have been identified in the heaviest known even-Z N = 84 isotone 158W, which lies in a region of one-proton emitters and the two-proton drip line. The observation of γ-ray transitions feeding the ground state establishes the excitation energy of the yrast 6+ state confirming the spin-gap nature of the α-decaying 8+ isomer. The 8+ isomer is also expected to be unbound to two-proton emission but no evidence for this decay mode was observed. An upper limit for the two-proton decay branch has been deduced as b 2 p ≤ 0.17% at the 90% confidence level. The possibility of observing two-proton emission from multiparticle isomers in nearby nuclides is considered.

Detailed spectroscopy of 193Bi

An experiment aiming to study shape coexistence in 193Bi has been performed. Due to its transitional character, it has an exceptionally large number of structures identified close to the yrast line. Many new states have been found, significantly extending the previously known level scheme of 193Bi, including several new rotational bands. The π i13/2 band was extended to I π = 45/2+. The I π = 31/2+ member of the π i13/2 band was found to de-excite also to a long-lived isomeric state. This isomeric state is located at 2350 keV and has a spin and parity of 29/2+. The half-life of the isomeric state was measured to be 85(3) μs and it decays via the emission of an 84 keV E2 transition. A level …

Identification of a 6.6μs isomeric state in Ir175

Spectroscopy of 193Bi

Shapes and Collectivity in Neutron Deficient Even-Mass 188–198Pb Isotopes

The neutron deficient 188−198Pb isotopes have been studied in a Coulomb excitation measurement employing the Miniball spectrometer and radioactive beams from REX-ISOLDE, CERN. These isotopes are of particular importance as they lie in a transitional region, where the intruding structures, associated with different deformed shapes, come down in energy close to the spherical ground state. For detailed analysis of the Coulomb excitation data, the understanding of the beam composition is essential. peerReviewed

Combined in-beam electron andγ-ray spectroscopy ofHg184,186

By exploiting the SAGE spectrometer a simultaneous measurement of conversion electrons and {gamma} rays emitted in the de-excitation of excited levels in the neutron-deficient nuclei {sup 184,186}Hg was performed. The light Hg isotopes under investigation were produced using the 4n channels of the fusion-evaporation reactions of {sup 40}Ar and {sup 148,150}Sm. The measured K- and L-conversion electron ratios confirmed the stretched E2 nature of several transitions of the yrast bands in {sup 184,186}Hg. Additional information on the E0 component of the 2{sub 2}{sup +}{yields}2{sub 1}{sup +} transition in {sup 186}Hg was obtained.

Identification of sub- μs isomeric states in the odd-odd nucleus Au178

The neutron-deficient gold (Z=79) isotopes in the vicinity of the neutron midshell N=104 provide prolific examples of shape coexistence and isomerism at low excitation energy. They can be probed via a number of different experimental techniques. In this study, two new isomeric states with half-lives of 294(7) and 373(9) ns have been observed in the neutron-deficient odd-odd nuclide Au178 (N=99) in an experiment at the RITU gas-filled separator at JYFL, Jyvaskyla. This result was achieved due to the use of a segmented planar germanium detector with a high efficiency at low energies. By applying the recoil-decay tagging technique, they were assigned to decay to two different long-lived α-deca…

Confirming band assignments in $^{167}$ytterbium with gamma-gamma-electron triple-coincidence spectroscopy

International audience; Multipolarity measurements are presented for transitions in the deformed odd-mass nucleus$^{167}$ Yb in support of tentative spin assignments and level interpretations based upon the cranked-Nilsson model. Internal-conversion coefficients were measured with the SAGE (Silicon And GErmanium) spectrometer confirming several E2 transition assignments. The array of high-purity germanium detectors enabled the recording of high-multiplicity events from which $\gamma\gamma\gamma$ and $\gamma\gamma e^{-}$ data sets were extracted and the technique of high-fold $\gamma$ -ray gating was demonstrated to cleanly isolate transitions of interest.

Shell-Structure and Pairing Interaction in Superheavy Nuclei: Rotational Properties of theZ=104NucleusRf256

The rotational band structure of the $Z=104$ nucleus $^{256}\mathrm{Rf}$ has been observed up to a tentative spin of $20\ensuremath{\hbar}$ using state-of-the-art $\ensuremath{\gamma}$-ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-$j$ orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing i…

Fine structure in the α decay of Lu156 and Ta158

Do nuclei go pear-shaped? Coulomb excitation of 220Rn and 224Ra at REX-ISOLDE (CERN)

Artículo escrito por muchos autores, sólo se referencian el primero, los autores que firman como Universidad Autónoma de Madrid y el grupo de colaboración en el caso de que aparezca en el artículo

Spin-dependent evolution of collectivity in 112Te

The evolution of collectivity with spin along the yrast line in the neutron-deficient nucleus 112Te has been studied by measuring the reduced transition probability of excited states in the yrast band. In particular, the lifetimes of the 4+ and 6+ excited states have been determined by using the recoil distance Doppler-shift method. The results are discussed using both large-scale shell-model and total Routhian surface calculations. peerReviewed

Detailed spectroscopy of 195Bi

An experiment focused on the study of shape coexistence and new high-spin structures in 195 Bi has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the 13 / 2 + isomeric state was extended up to I π = ( 49 / 2 + ) and an energy of 5706 keV. The I π = 31 / 2 + member of the π i 13 / 2 band was also found to feed a new long-lived isomeric state with an excitation energy of 2616 keV and a spin and parity of I π = 29 / 2 + . The half-life …

First observation of excited states of 173Hg

The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of the decay of excited states via γ radiation are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighboring neutron-deficient Hg nuclei. In addition to the γ -ray spectroscopy, the α decay of this nucleus has been measured yielding superior precision to earlier measurements. peerReviewed

First identification of rotational band structures inRe9175166

Despite that it is more than 100 years since the atomic nucleus was first dis- covered by Ernest Rutherford and coworkers, many of its features still elude our understanding. The fact that the fundamental interactions between the nuclear constituents; nucleons, and ultimately quarks, are not yet known in detail, and the complexity of the nuclear many-body system compound the great challenges facing theoretical interpretations of experimental data. It is therefore important to focus on distinct phenomena where experimental mea- surements can be compared with theoretical predictions, providing stringent tests of theory. One such area is the nuclear phenomenology of collective excitations rela…

High-spin states of $^{218}$Th

Abstract High-spin states in the N = 128 nucleus 218Th have been investigated following fusion–evaporation reactions, using the recoil-decay tagging technique. Due to the short-lived nature of the ground state of 218Th prompt γ rays have been correlated with the α decay of the daughter nucleus 214Ra. The level scheme representing the decay of excited states has been extended to (16+) with the observation of six previously unreported transitions. The observations are compared with the results of shell model calculations and within the context of the systematics of neighbouring nuclei.

Isomer-tagged differential-plunger measurements in 113Xe

The 278-keV M2 γ decay from the νh11/2 isomeric state in 113Xe has been observed for the first time using the recoil-isomer tagging technique. The half-life of the isomer has been measured to be 6.9(3) μs. The derived B(M2) value is in agreement with the trend of systematic measurements of M2 transition strengths in neutron-deficient tellurium and tin isotopes. The lifetime of the first excited state in the νh11/2 band has been measured using the recoil distance Doppler-shift method. The extracted B(E2) value has been compared to theoretical CD-Bonn calculations and recent lifetime measurements in 109Te. This comparison of B(E2) values has been used to shed light on the possible influence o…

Characterizing the atomic mass surface beyond the proton drip line via {\alpha}-decay measurements of the {\pi}s1/2 ground state of 165Re and the {\pi}h11/2 isomer in 161Ta

The α-decay chains originating from the πs1/2 and πh11/2 states in 173Au have been investigated following fusion-evaporation reactions. Four generations of α radioactivities have been correlated with 173Aum leading to a measurement of the α decay of 161Tam. It has been found that the known α decay of 161Ta, which was previously associated with the decay of the ground state, is in fact the decay of an isomeric state. This work also reports on the first observation of prompt γ rays feeding the ground state of 173Au. This prompt γ radiation was used to aid the study of the α-decay chain originating from the πs1/2 state in 173Au. Three generations of α decays have been correlated with this stat…

Competing single-particle and collective states in the low-energy structure of 113I

To understand the low-energy structure of the neutron deficient iodine isotopes, lifetimes for the low-lying 9/2+ and 11/2+ positive-parity states in 113I have been measured as τ = 28(4) ps and τ = 3.7(7) ps, respectively. The lifetime for the 11/2− state, which feeds the 9/2+ and 11/2+ states, was remeasured with improved accuracy as τ = 216(7) ps. The reduced transition probability, B(E2) = 32(5) W.u., for the 9/2+ → 5/2+ transition agrees with that calculated within the shell model using a Hamiltonian based on the charge-dependent Bonn nucleon-nucleon interaction. In contrast, the much larger transition probability, B(E2) = 209(39) W.u., measured for the 11/2+ → 7/2+ transition has been …

Lifetime measurements of excited states in W162 and W164 and the evolution of collectivity in rare-earth nuclei

Lifetimes of the first excited 2(+) states in the extremely neutron- deficient W-162 and W-164 nuclei have been measured using the recoil distance Doppler shift technique. Experimental B(E2) data f ...

Spectroscopy of proton-rich 66^Se up to J^�� = 6^+: isospin-breaking effect in the A = 66 isobaric triplet

Candidates for three excited states in the 66^Se have been identified using the recoil-�� tagging method together with a veto detector for charged-particle evaporation channels. These results allow a comparison of mirror and triplet energy differences between analogue states across the A = 66 triplet as a function of angular momentum. The extracted triplet energy differences follow the negative trend observed in the f_7/2 shell. Shell-model calculations indicate a continued need for an additional isospin non-conserving interaction in addition to the Coulomb isotensor part as a function of mass.

Spectroscopy of At 201 including the observation of a shears band and the 29/2 + isomeric state

The excited states of 201At were studied and an isomeric 29/2 + state [T1/2 = 3.39(9) μs] was identified by using a fusion-evaporation reaction, a gas-filled recoil separator, and recoil gating techniques. The 29/2 + state is suggested to originate from the π(h9/2) ⊗ |200Po;11− configuration, and it decays through the 269- and 339-keV E2- and E3-type transitions, respectively. Moreover, a cascade of magnetic dipole transitions that is suggested to originate from a shears band was observed by using recoil-gated γ − γ (−γ ) coincidence techniques. peerReviewed

Lifetime measurement of the first excited2+state in108Te

The lifetime of the first excited 2(+) state in the neutron deficient nuclide (108)Te has been measured for the first time, using a combined recoil decay tagging and recoil distance Doppler shift t ...

Study of Intermediate-spin States of $^{98}$Y

The nuclear structure of the odd–odd nucleus 98Y has been re-investigated by observing prompt γ rays emitted following the proton-induced fission of a 238U target, using the JUROGAM-II multidetector array. New highspin decays have been observed and placed in the level schemes using triple coincidences. The experimental level energies and γ-decay patterns are compared to GICM and QPRM calculations, assuming that this neutronrich N = 59 isotone is spherical at low energies and prolate deformed at intermediate spins. Web of Science 47 3 916 911