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論文

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

Konki, J.*; Khuyagbaatar, J.*; Uusitalo, J.*; Greenlees, P. T.*; Auranen, K.*; Badran, H.*; Block, M.*; Briselet, R.*; Cox, D. M.*; Dasgupta, M.*; et al.

Physics Letters B, 764, p.265 - 270, 2017/01

 被引用回数:10 パーセンタイル:19.68(Astronomy & Astrophysics)

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$$^{+13}_{-6}$$s were obtained for $$^{240}$$Es and $$^{236}$$Bk, respectively. Two groups of $$alpha$$ particles with energies $$E_{alpha}$$=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 probabilities in more neutron-deficient isotopes.

論文

Short-lived isomers in $$^{192}$$Po and $$^{194}$$Po

Andel, B.*; Andreyev, A.; Antalic, S.*; He${ss}$berger, F. P.*; Ackermann, D.*; Hofmann, S.*; Huyse, M.*; Kalaninov$'a$, Z.*; Kindler, B.*; Kojouharov, I.*; et al.

Physical Review C, 93(6), p.064316_1 - 064316_12, 2016/06

 被引用回数:0 パーセンタイル:100(Physics, Nuclear)

Isomeric states in $$^{194}$$Po and $$^{192}$$Po were studied at the velocity filter SHIP. The isotopes were produced in the fusion-evaporation reactions $$^{141}$$Pr($$^{56}$$Fe, $$p2n$$)$$^{194}$$Po and $$^{144}$$Sm($$^{51}$$V, $$p2n$$)$$^{192}$$Po. Several new $$gamma$$-ray transitions were attributed to the isomers and $$gamma$$-$$gamma$$ coincidences for both isomers were studied for the first time. The 459-keV transition earlier, tentatively proposed as de-exciting the isomeric level in $$^{194}$$Po, was replaced by a new 248-keV transition, and the spin of this isomer was reassigned from (11$$^{-}$$) to (10$$^{-}$$). The de-excitation of the (11$$^{-}$$) isomeric level in $$^{192}$$Po by the 154-keV transition was confirmed and a parallel de-excitation by a 733-keV (E3) transition to (8$$^{+}$$) level of the ground-state band was suggested. Moreover, side feeding to the (4$$^{+}$$) level of the ground-state band was proposed. The paper also discusses strengths of transitions de-exciting 11$$^{-}$$ isomers in neighboring Po and Pb isotopes.

論文

Shell evolution beyond $$N$$=40; $$^{69,71,73}$$Cu

Sahin, E.*; Doncel, M.*; Sieja, K.*; de Angelis, G.*; Gadea, A.*; Quintana, B.*; G$"o$rgen, A.*; Modamio, V.*; Mengoni, D.*; Valiente-Dob$'o$n, J. J.*; et al.

Physical Review C, 91(3), p.034302_1 - 034302_9, 2015/03

 被引用回数:19 パーセンタイル:14.17(Physics, Nuclear)

The level structure of the neutron-rich $$^{69}$$Cu, $$^{71}$$Cu, and $$^{73}$$Cu isotopes was investigated using multinucleon transfer reactions at Laboratori Nazionali di Legnaro using the AGATA Demonstrator array coupled to the PRISMA magnetic spectrometer. Lifetimes of excited states in Cu nuclei were measured with the recoil-distance Doppler-shift method. The resulting electromagnetic matrix elements for transitions from excited states in $$^{69,71,73}$$Cu nuclei was used to assess the collective or single-particle character of these states. The results are compared with predictions of large-scale shell-model calculations, showing how the proton pf shell evolve as neutrons fill the 1g$$_{9/2}$$ orbital.

論文

Signature of the Z=82 shell closure in $$alpha$$-decay process

Andreyev, A. N.*; Huyse, M.*; Van Duppen, P.*; Qi, C.*; Liotta, R. J.*; Antalic, S.*; Ackermann, D.*; Franchoo, S.*; He${ss}$berger, F. P.*; Hofmann, S.*; et al.

Physical Review Letters, 110(24), p.242502_1 - 242502_5, 2013/06

 被引用回数:56 パーセンタイル:7.43(Physics, Multidisciplinary)

$$alpha$$-decay data for more than 20 nuclei of the most neutron-deificient isotopes in the region from lead to thorium was obtained. The combined analysis allowed us for the first time to clearly show that crossing the Z=82 shell to higher proton numbers strongly accelerates the $$alpha$$ decay. The analysis support the conjecture that both the N=126 and Z=82 shell closures stongly influence the $$alpha$$-formation probability.

論文

First prompt in-beam $$gamma$$-ray spectroscopy of a superheavy element; The $$^{256}$$Rf

Rubert, J.*; Dorvaux, O.*; Gall, B. J. P.*; Greenlees, P. T.*; Asfari, Z.*; Piot, J.*; Andersson, L. L.*; 浅井 雅人; Cox, D. M.*; Dechery, F.*; et al.

Journal of Physics; Conference Series, 420, p.012010_1 - 012010_10, 2013/03

 被引用回数:0 パーセンタイル:100

初めての超重元素即発インビーム$$gamma$$線分光実験を$$^{256}$$Rfを対象に行った。MIVOC法を用いた大強度$$^{50}$$Tiビームの開発を行い、実験を成功させた。$$^{256}$$Rfの回転励起状態をスピン20 $$hbar$$まで観測し、その慣性能率を導出した。これらのデータから、陽子数104には大きな変形閉殻が存在しないことが明らかとなった。

論文

$$beta$$-delayed fission of $$^{192,194}$$At

Andreyev, A. N.*; Antalic, S.*; Ackermann, D.*; Bianco, L.*; Franchoo, S.*; Heinz, S.*; He${ss}$berger, F. P.*; Hofmann, S.*; Huyse, M.*; Kalaninov$'a$, Z.*; et al.

Physical Review C, 87(1), p.014317_1 - 014317_8, 2013/01

 被引用回数:19 パーセンタイル:19.46(Physics, Nuclear)

By using the recoil-fission correlation technique, the exotic process of beta-delayed fission ($$beta$$DF) was unambiguously identified in the very neutron-deficient nuclei $$^{192,194}$$At in experiments at the velocity filter SHIP at Gesellschaft f$"u$r Schwerionenforschung (GSI). The upper limits for the total kinetic energy release in fission of $$^{194,196}$$Po, being the daughter of $$^{192,194}$$At after $$beta^{+}/EC$$ decay, were estimated. The possibility of an unusually high $$beta^{+}$$DF probability $$^{192}$$At is discussed.

論文

Shell-structure and pairing interaction in superheavy nuclei; Rotational properties of the $$Z$$=104 nucleus $$^{256}$$Rf

Greenlees, P. T.*; Rubert, J.*; Piot, J.*; Gall, B. J. P.*; Andersson, L. L.*; 浅井 雅人; Asfari, Z.*; Cox, D. M.*; Dechery, F.*; Dorvaux, O.*; et al.

Physical Review Letters, 109(1), p.012501_1 - 012501_5, 2012/07

 被引用回数:46 パーセンタイル:10.86(Physics, Multidisciplinary)

104番元素$$^{256}$$Rfの回転励起構造をインビーム$$gamma$$線核分光の手法により初めて観測することに成功した。$$^{256}$$Rfは回転励起構造が観測された最も重い原子核であり、今回の結果は重い極限に位置する原子核の一粒子軌道殻構造と対相関に関する貴重な情報を与える。今回の実験で得られた$$^{256}$$Rfの回転状態の慣性能率の値は、陽子数104における変形閉殻の存在を明確に否定し、近年の数多くの自己無撞着平均場モデルの予測と異なる結果を示した。

論文

Alpha-$$gamma$$ decay studies of $$^{253}$$No and its daughter products $$^{253}$$Md, $$^{249}$$Fm

He${ss}$berger, F. P.*; Antalic, S.*; Ackermann, D.*; Kalaninov$'a$, Z.*; Heinz, S.*; Hofmann, S.*; Streicher, B.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.

European Physical Journal A, 48(5), p.75_1 - 75_9, 2012/05

 被引用回数:20 パーセンタイル:23.13(Physics, Nuclear)

Nuclear structure and decay of the isotope $$^{253}$$No and its decay products $$^{249}$$Fm and $$^{253}$$Md were investigated by means of $$alpha$$-$$gamma$$ spectroscopy. Besides the established strong $$alpha$$ transitions from the 9/2$$^{-}$$[734] Nilsson level in $$^{249}$$Fm, populated predominantly by the $$alpha$$ decay of $$^{253}$$No, into the ground-state(gs) rotational band, a couple of weaker $$alpha$$ lines were observed and placed into the $$^{249}$$Fm level scheme. The transition from the 7/2$$^{-}$$ level in $$^{249}$$Es, populated by the $$alpha$$ decay of $$^{253}$$Md, into the 9/2$$^{+}$$ member of the gs rotational band, so far established for other odd-mass Es isotopes, was observed clearly. The GEANT4 simulations were performed to investigate the influence of energy summing between $$alpha$$ particles and conversion electrons (CE) on the shape of the $$alpha$$ spectra at different implantation energies, leading to evidence for a weak $$alpha$$ decay branch of $$^{253}$$No into the gs of $$^{249}$$Fm or the ground-state rotational band, respectively.

論文

Isomeric states in $$^{253}$$No and $$^{253}$$Fm

Antalic, S.*; He${ss}$berger, F. P.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Kalaninov$'a$, Z.*; Kindler, B.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.

European Physical Journal A, 47(5), p.62_1 - 62_12, 2011/05

 被引用回数:23 パーセンタイル:17.81(Physics, Nuclear)

Nuclear structure and decay of isomer in $$^{253}$$No were investigated. The isotope was produced by the reaction $$^{48}$$Ca+$$^{207}$$Pb. The excitation energy of the known single-particle isomeric state (5/2$$^{+}$$[622]) was measured by delayed coincidence between $$gamma$$-rays and implanted evaporation residues and was placed into the level scheme. In addition, decay of a high-lying multi-quasiparticle isomer in $$^{253}$$No was studied using e$$^{-}$$-$$gamma$$ coincidence measurements. A rotational band populated by its de-excitation was identified in $$^{253}$$No. A new isomeric state in $$^{253}$$Fm was observed and a partial-level scheme for this isotope is suggested. In addition $$gamma$$ transitions from excited levels are reproduced for $$^{253}$$Md.

論文

Decay studies of K isomer in $$^{254}$$No

He${ss}$berger, F. P.*; Antalic, S.*; Sulignano, B.*; Ackermann, D.*; Heinz, S.*; Hofmann, S.*; Kindler, B.*; Khuyagbaatar, J.*; Kojouharov, I.*; Kuusiniemi, P.*; et al.

European Physical Journal A, 43(1), p.55 - 66, 2010/01

 被引用回数:59 パーセンタイル:4.96(Physics, Nuclear)

$$gamma$$-rays decay study of two K isomers in $$^{254}$$No was performed. Two new transitions of 778 and 856 keV could be attributed to the decay pattern of $$^{254m1}$$No (T$$_{1/2}$$=275 ms). The population of an excited band built up on this isomer ($$K$$$$^{pi}$$=8$$^{-}$$) by the decay of $$^{252m2}$$No (198 $$mu$$s) could be proven. A spontaneous fission branch of 2.0$$times$$10$$^{-4}$$ was measured for $$^{252m1}$$No, and upper limit of 1.2$$times$$10$$^{-4}$$ was estimated for $$^{252m2}$$No. These values demonstrate the high stability of multi-quasiparticle configuration against spontaneous fission.

論文

Di-nuclear systems studied with the velocity filter SHIP

Heinz, S.*; Comas, V.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Burkhard, H. G.*; Gan, Z.*; Heredia, J.*; Khuyagbaatar, J.*; Kindler, B.*; et al.

European Physical Journal A, 38(2), p.227 - 232, 2008/11

 被引用回数:22 パーセンタイル:20.83(Physics, Nuclear)

Various nuclear reactions like quasi-fission, fusion-fission or particle and cluster evaporation from excited compound nuclei were studied in heavy-ion reactions by using the velocity filter SHIP of GSI. The velocity distributions were measured for the heavier nuclei produced by bombarding $$^{25}$$Mg, $$^{64}$$Ni to the target nuclei $$^{206,207}$$Pb at energies of 5.9 MeV/A and 8.7 MeV/A. In addition to the evaporation residues produced in the fusion reactions, we found evidence for rotation and quasi-fission of nuclear molecules. The break-up of the systems showed a preferred clustering leading to isotopes in the region 84 $$le$$ $$Z$$ $$le$$ 88 and 122 $$le$$ $$N$$ $$le$$ 127.

論文

Decay studies of neutron-deficient lawrencium isotopes

Antalic, S.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; Leino, M.*; Lommel, B.*; et al.

European Physical Journal A, 38(2), p.219 - 226, 2008/11

 被引用回数:27 パーセンタイル:16.86(Physics, Nuclear)

The radioactive decay of the isotopes $$^{254-256}$$Lr and their daughter products was investigated by means of $$alpha$$, prompt $$alpha-gamma$$ and delayed conversion electron$$-gamma$$ coincidence spectroscopy. The experiment was carried out at GSI by using the velocity filter SHIP to separate evaporation residues, produced in the reaction $$^{48}$$Ca+$$^{209}$$Bi, from the primary beams. In $$^{255}$$Lr, a second short-lived isomer with a half-life of 1.91 ms was found. For $$^{254,256}$$Lr, new data for $$gamma$$ transitions of levels in $$^{250,252}$$Md populated by $$alpha$$ decay were observed. The constructed level schemes are useful for the nuclear structure theory.

論文

Orientation effects of deformed $$^{238}$$U target nuclei on the fusion probability for the heavy element synthesis

西尾 勝久; Hofmann, S.*; 池添 博; He${ss}$berger, F. P.*; Ackermann, D.*; Antalic, S.*; Comas, V. F.*; Gan, Z.*; Heinz, S.*; Heredia, J. A.*; et al.

Nuclear Physics A, 805(1-4), p.516 - 518, 2008/06

The effects of the orientation of the deformed $$^{238}$$U target nuclei were investigated in the reaction of $$^{30}$$Si+$$^{238}$$U. The cross-sections of the system to overcome the Coulomb barrier were determined by measuring the fission cross-sections at JAEA-tandem accelerator, from which the Coulomb barrier height for the collision of $$^{30}$$Si to the polar side and the equatorial side of $$^{238}$$U were determined. The evaporation residue (ER) cross-sections were determined at the velocity filter SHIP of GSI. Significant enhancement of the cross-sections of $$^{264}$$Sg(4n) in the sub-barrier energy indicates the lowering of the Coulomb barrier at the Polar collisions. However, competition between fusion and quasifission was implied. The cross-sections for $$^{263}$$Sg(5n) measured at the above barrier energy indicated that there is no significant fusion hindrance at the equatorial collisions. In this contribution, the systematic behavior of the orientation effects of $$^{238}$$U is discussed by using additionally the data of $$^{16}$$O+$$^{238}$$U and $$^{48}$$Ca+$$^{238}$$U.

論文

Isomeric states in $$^{214}$$Th and $$^{213}$$Th

Khuyagbaatar, J.*; Hofmann, S.*; He${ss}$berger, F. P.*; Ackermann, D.*; Antalic, S.*; Burkhard, H. G.*; Heinz, S.*; Kindler, B.*; Lisetskiy, A. F.*; Lommel, B.*; et al.

European Physical Journal A, 34(4), p.355 - 361, 2007/12

 被引用回数:7 パーセンタイル:47.56(Physics, Nuclear)

Isomeric states in $$^{214}$$Th and $$^{213}$$Th were produced in the fusion-evaporation reactions of $$^{54}$$Cr + $$^{164}$$Dy and identified by means of $$gamma$$-rays from the isomeric states. The life-times were determined by measureing the time difference between the signals of the implanted evaporation residues ($$^{213,214}$$Th) and the $$gamma$$-rays signals, and were obtained to be 1.24 $$mu$$s for $$^{214}$$Th and 1.4 $$mu$$s for $$^{213}$$Th. The proton configuration betweens the orbitals of 1h$$_{9/2}$$ and 2f$$_{7/2}$$ was assigned to the isomeric states in $$^{214}$$Th.

論文

Measurement of evaporation residue and fission cross sections of the reaction $$^{30}$$Si + $$^{238}$$U at subbarrier energies

西尾 勝久; Hofmann, S.*; 池添 博; He${ss}$berger, F. P.*; Ackermann, D.*; Antalic, S.*; Comas, V. F.*; Gan, Z.*; Heinz, S.*; Heredia, J. A.*; et al.

Journal of Nuclear and Radiochemical Sciences, 8(2), p.73 - 78, 2007/10

Effects of the prolate deformation of $$^{238}$$U on fusion were studied in the reaction $$^{30}$$Si + $$^{238}$$U at bombarding energies close to the Coulomb barrier. The fission cross section was measured at JAEA tandem accelerator to see the enhancement of the cross section in the subbarrier energy due to the lowering of the Coulomb barrier at the collision of the projectile to polar side of $$^{238}$$U. Evaporation residue cross sections were measured at UNILAC of GSI by using the velocity filter SHIP to determine the fusion probability. In the subbarrier region, we could produce isotope $$^{264}$$Sg by 4n channel, but fusion hindrance was implied in the analysis. At above barrier energies, we produced $$^{263}$$Sg by 5n channel. The analysis suggests that there is no fusion hindrance at the equatorial collisions.

論文

Identification of a K isomer in $$^{252}$$No

Sulignano, B.*; Heinz, S.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Antalic, S.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; Lommel, B.*; et al.

European Physical Journal A, 33(4), p.327 - 331, 2007/09

 被引用回数:64 パーセンタイル:4.12(Physics, Nuclear)

The $$K$$-isomer with a half-life of 100 ms has been discovered in the nucleus $$^{252}$$No. The nucleus was produced in the fusion-evaporation reacion $$^{206}$$Pb($$^{48}$$Ca,2n)$$^{252}$$No. The experiment was carried out at the velocity filter SHIP of GSI. The isomeric state is located at an excitation energy of 1254 keV and is interpreted as a two quasi-neutron state with $$K$$=8$$^{-}$$. The isomeric state has direct connection to the rotational states of 8$$^{+}$$ in $$^{252}$$No. Also the rotational states of 6$$^{+}$$ and 4$$^{+}$$ was feeded via the octupole band with $$K$$=2$$^{-}$$. The isomeric state and the ground state was populated with the equal intensity in the fusion-evaporation reaction.

論文

The Reaction $$^{48}$$Ca+$$^{238}$$U $$rightarrow$$ $$^{286}$$112$$^{*}$$ studied at the GSI-SHIP

Hofmann, S.*; Ackermann, D.*; Antalic, S.*; Burkhard, H. G.*; Comas, V. F.*; Dressler, R.*; Gan, Z.*; Heinz, S.*; Heredia, J. A.*; He${ss}$berger, F. P.*; et al.

European Physical Journal A, 32(3), p.251 - 260, 2007/06

 被引用回数:221 パーセンタイル:0.35(Physics, Nuclear)

The fusion reaction of $$^{48}$$Ca projectiles with$$^{238}$$U target nuclei was studied at the velocity filter SHIP of GSI. Two decay chains were measured, which fully confirm data that were previously assigned to the isotope $$^{283}$$112 in experiments at the Flerov Laboratory in Dubna. Two other events are consistent with a 50 % spontaneous fission (SF) branch of this isotope. The mean value obtained for the half-life of $$^{283}$$112 is (6.9$$^{+6.9}_{-2.3}$$) s, the $$alpha$$ energy is (9.520$$pm$$0.015) MeV, and the total kinetic energy (TKE) of SF is (238$$pm$$14) MeV. The half-life of the $$alpha$$ decay daughter nucleus $$^{279}$$Ds is (0.18$$^{+0.32}_{-0.07}$$) s, and the TKE of SF is (210$$^{+32}_{-11}$$) MeV. The cross-section deduced from all four events is (0.72$$^{+0.58}_{-0.35}$$) pb, measured at an excitation energy of 34.6 MeV of the compound nucleus $$^{286}$$112.

論文

Measurement of evaporation residue cross-sections of the reaction $$^{30}$$Si + $$^{238}$$U at subbarrier energies

西尾 勝久; Hofmann, S.*; He${ss}$berger, F. P.*; Ackermann, D.*; Antalic, S.*; Comas, V. F.*; Gan, Z.*; Heinz, S.*; Heredia, J. A.*; 池添 博; et al.

AIP Conference Proceedings 891, p.71 - 79, 2007/03

重イオン融合反応$$^{30}$$Si+$$^{238}$$UによりSg同位体を合成し、この生成断面積を調べた。実験は、ドイツ重イオン研究所(GSI)で行った。反応エネルギーE$$_{c.m.}$$=144MeVにおいて、$$^{263}$$Sgから始まる3つの$$alpha$$崩壊連鎖を観測し、断面積67pbを得た。サブバリヤエネルギーE$$_{c.m.}$$=133MeVで、新同位体$$^{264}$$Sgを3つ合成し、断面積10pbを得た。これは自発核分裂で崩壊し、半減期は120msであった。これら断面積を統計モデル計算と比較した。融合過程においては、$$^{238}$$Uの変形を取り入れたチャンネル結合法で捕獲断面積を決定した。この値は、原子力機構のタンデム加速器を用いて行った$$^{30}$$Si+$$^{238}$$Uの核分裂断面積とよく一致した。E$$_{c.m.}$$=133MeVでの断面積の値は、一次元モデルに比べて10$$^{4}$$倍大きな値であり、ウランの変形によって断面積が増加することがわかった。しかし、計算との不一致から、準核分裂が何割か存在することが示唆された。クーロン障壁より高いエネルギーE$$_{c.m.}$$=144MeVでは$$^{30}$$Siは$$^{238}$$Uの赤道面と接触できる。$$^{263}$$Sgの生成断面積67pbは、統計モデル計算値によく一致し、融合に阻害がなかった。これは、赤道面衝突が融合に有利であることを示唆している。

論文

Studies of $$^{rm 213g,m}$$Ra and $$^{rm 214g,m}$$ by $$alpha$$ and $$gamma$$ decay

Kuusiniemi, P.*; He${ss}$berger, F. P.*; Ackermann, D.*; Antalic, S.*; Hofmann, S.*; 西尾 勝久; Sulignano, B.*; Kojouharov, I.*; Mann, R.*

European Physical Journal A, 30(3), p.551 - 559, 2006/12

 被引用回数:8 パーセンタイル:47.02(Physics, Nuclear)

$$^{214}$$Raと$$^{213}$$Raの崩壊核分光実験を$$alpha$$及び$$gamma$$崩壊の測定によって調べた。これらの原子核は$$^{170}$$Er($$^{48}$$Ca,xn)$$^{218-x}$$Ra又は$$^{170}$$Er($$^{50}$$Ti,3n)$$^{217}$$Thで生成される$$^{217}$$Thの$$alpha$$崩壊核種として生成した。蒸発残留核は、ドイツGSIにおける反跳生成核分離装置SHIPで分離され、焦点におけるシリコン検出器で$$alpha$$崩壊を測定し、ゲルマニウム検出器で$$gamma$$線を測定した。本実験から、次のことが明らかになった。(1)$$^{209}$$Rnの励起準位に崩壊する$$^{213}$$Raの$$alpha$$線と$$gamma$$線のコインシデンスデータから、新たに3つの$$^{209}$$Rnの励起準位のスピン・パリティを決定した。このうち、511keVの励起準位に遷移する$$alpha$$崩壊を初めて観測した。(2)$$^{214}$$Raの8$$^{+}$$アイソマーから、$$^{210}$$Rnの8$$^{+}$$アイソマに遷移する$$alpha$$崩壊を初めて観測した。計算で決定したHindrance Factorが1.0であることから、同じスピン間の遷移であることを確認した。

論文

Alpha-$$gamma$$ decay studies of $$^{255}$$Rf, $$^{251}$$No and $$^{247}$$Fm

He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Antalic, S.*; Kindler, B.*; Kojouharov, I.*; Kuusiniemi, P.*; Leino, M.*; Lommel, B.*; Mann, R.*; et al.

European Physical Journal A, 30(3), p.561 - 569, 2006/12

 被引用回数:42 パーセンタイル:9.42(Physics, Nuclear)

$$^{255}$$Rf, $$^{251}$$No及び$$^{247}$$Fmについて、$$alpha$$線と$$gamma$$線の検出による崩壊核分光実験を行った。実験は、ドイツ重イオン研究所の線形加速器施設UNILACにおける反跳生成核分離装置SHIPを用いて行った。SHIPで分離された蒸発残留核を焦点に設置したシリコン検出器に打ち込んだ。この検出器で$$alpha$$崩壊を検出し、また近くに設けたGe検出器で$$gamma$$線を検出した。これら同位体は、$$^{207}$$Pb($$^{50}$$Ti,2n)$$^{255}$$Rf及びこの$$^{255}$$Rfの$$alpha$$崩壊核種として生成し、さらに$$^{206}$$Pb($$^{48}$$Ca,3n)$$^{251}$$No反応及びこの$$^{251}$$Noの$$alpha$$崩壊核種として生成した。解析から次のことがわかった。(1)$$^{251}$$Noには半減期1.0秒のアイソマがあることがわかっていたが、このエネルギー準位が106keVであることがわかった。(2)また、$$^{251}$$Noには2$$mu$$sの半減期を持つ第2のアイソマがあり、$$^{206}$$Pb($$^{48}$$Ca,3n)$$^{251}$$No反応で直接生成されることがわかった。このアイソマは、2本の$$gamma$$線とコインシデンスし、解析から励起エネルギーが1700keV以上の準位にあることが示唆された。この2本の$$gamma$$線は、$$^{255}$$Rfの$$alpha$$崩壊につづく$$gamma$$遷移と一致した。

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