K. Heiguchi

Theβ+ decay of the new isotope86Mo and the first observation of86mNb

Theβ+ decay of86Mo has been firstly investigated by means ofβγ spectroscopy. The86Mo nuclei were produced by fusion-evaporation reactions of54Fe (35Cl, 1 p2n) and58Ni (32S,2p 2n) at beam energies of 103 and 120 MeV, respectively. Threeγ rays of 47.3, 49.8 and 187.0 keV were unambiguously identified to follow theβ+ decay of86Mo by results ofXγ andβγ coincidence and cross-bombardment. A half life and a maximumβ+-ray energy of86Mo were determined to be 19.6±1.1 s and 3.9±0.4 MeV, respectively. A decay scheme of86Mo is proposed in this article. Furthermore, a decay of86Nb has been studied using the same combinations of projectiles and targets, and a newβ-decaying isomer86mNb was observed with a half life of 56.3±8.3 s.

The level structure of 87Nb

Abstract The level structure of 87 Nb has been studied through β-decay of 87 Mo activity produced by the 58 Ni( 32 S, 2pn) reaction and through in-beam γ-ray measurements in the 58 Ni( 32 S, 3pγ) 87 Nb reaction. In the β-decay study, the decay scheme of 87 Mo is constructed firstly from γ-ray energies, intensities of γ-rays and conversion electrons, and γ-, βγ- and γ(ce)-coincidence relations. Spins and parities of the low-lying statesof 87 Nb and 87 Zr were also investigated. In the in-beam study, intensities, coincidence relations and angular distributions of γ-rays were measured in coincidence with charged particles evaporated from the compound nuclei. Then high-spin states of J π ⩽ ( 33+ 2 ) in 87 Nb were established in this study. Systematic behavior in the level structures of N = 46 isotones, and the comparison between those of 85 Y and 87 Nb, are discussed.

Nuclear Magnetic Resonance on Oriented 137m,gCe and 139Ce

Nuclear magnetic resonances of oriented 137m,g Ce and 139 Ce in an iron host have been measured at 7 mK. From the resonance-shift measurement of 137m Ce, the magnetic hyperfine splitting frequency ν=|µ B HF / I h |, the magnetic moment µ and the magnetic hyperfine field B HF were derived as ν=54.25(1) MHz, \(|\mu(^{137\text{m}}\text{Ce}, \frac{11}{2}^{-})|=1.01(4)\mu_{\text{N}}\) and B HF ( 137 Ce Fe )=-38.8(10) T, respectively. The resonance frequencies of 137g Ce Fe and 139 Ce Fe at the external field of 0.2 T were found to be 188.3(5) and 208.5(5) MHz, respectively. With the measured hyperfine field, the magnetic moments of 137g Ce and 139 Ce were deduced as \(|\mu(^{137\text{g}}\text{Ce}, \frac{3}{2}^{+})|=0.96(4)\mu_{\text{N}}\) and \(|\mu(^{139}\text{Ce}, \frac{3}{2}^{+})|=1.06(4)\mu_{\text{N}}\). The measured magnetic moments are compared with the theoretical values based on the core-polarization model.

NMR-ON measurements of123, 124, 131I in nickel

The magnetic hyperfine splitting frequencies of123INi,124INi and131INi in a zero external magnetic field have been determined by the NMR-ON method as 258.9(1), 165.9(1) and 179.5(2) MHz, respectively. With the known values of the magnetic moments, the magnetic hyperfine fields have been deduced:BHF(123INi)=30.17(5) T,BHF(124INi)=30.14(9) T,BHF(131INi)=30.06(4) T; the weighted average isBHF(INi)=30.11(4) T. The small difference of theBHF(131INi) with those of123INi and124INi is discussed comparing with results of the hyperfine splitting frequency of iodine in iron host.

Satellite line structure in NMR-ON on206BiFe and182ReFe

Nuclear magnetic resonance on oriented206BiFe and182ReFe has been measured using recoil implanted samples. Clearly resolved satellite structures were found for both systems. By annealing at an appropriate temperature, the resonance width was reduced. The satellite line structure for182ReFe was studied with various annealing temperatures. The ratio of the resonance strength changed with the annealing temperature. The resonances for182ReFe were also measured in external magnetic fields of 0.1, 0.2 and 0.4 T. The resonance frequencies for the satellite structure at an external magnetic field of 0.2 T were determined:v1=691.7(3),v2=684.4(2),v3=687.2(2) MHz for206BiFe;v1=231.15(5),v2=230.20(5) for182ReFe. The origin of the satellite structure is discussed. The effective relaxation time of182ReFe at 8 mK and external magnetic field of 0.2 T was determined to be 18.6(6) s using a single-exponential fit.

Nuclear magnetic resonance on oriented76,77,82Br in Fe

Nuclear magnetic resonance on oriented76,77,82BrFe has been measured using recoil-implanted samples. The magnetic hyperfine splitting frequency of82BrFe in a zero external magnetic field has been determined to be 201.90(3) MHz. The resonances of76BrFe and77BrFe were also observed in an external magnetic field of 0.2 T asv(76BrFe)=340.9(3) MHz andv(77BrFe)=403.5(2) MHz. With the known values of theg-factors, the hyperfine fields have been deduced:BHF(82BrFe)=81.397(27) T,BHF(76BrFe)=81.38(7) T. Theg-factor of77Br was determined to be |0.6487(4)|.

The β -decay of 88 Tc

Decay scheme, half life andQEC value of88Tc were deduced from aβ-decay study. The neutron deficient nucleus88Tc was produced by the58Ni(32S,pn)88Tc reaction using beam energies of 100, 101 and 105 MeV. The ground- and isomeric states of88Tc were found to decay to88Mo with similar half lives of 5.8±0.2 and 6.4±0.8 sec. The most probable spins and parities of these states are 3+ and 6+, respectively, though the order in energy could not be determined. TheQEC value was deduced to be 8.6±1.3 MeV.

Magnetic hyperfine fields of Nb andMo in nickel by NMR-ON of90Nb and93mMo

The magnetic hyperfine splitting frequencies of90NbNi and93mMoNi in an external magnetic field of 0.2 T have been determined by the NMR-ON method to be 18.52(7) and23.73(10) MHz, respectively. With the assumption of Knight shift factorK=0 and with the knowng-factors, the hyperfine fields of90NbNi and93mMoNi were deduced asBHF(90NbNi)=-4.118(16) T andBHF(93mMoNi)=-3.491(33) T. The rather long spin-lattice relaxation time of 32(5) min was observed for90NbNi at an external magnetic field of 0.2T and8 mK.

Nuclear magnetic moments of the ground states ofI124,I126, andI130

The nuclear magnetic moments of {sup 124}I, {sup 126}I, and {sup 130}I have been measured by the techniques of low-temperature nuclear orientation and nuclear magnetic resonance on oriented nuclei. The magnetic hyperfine splitting frequency {vert bar}{ital g}{mu}{sub {ital N}BHF}/{ital h}{vert bar} for {sup 124}I{ital Fe} was determined to be 630.2(2) MHz from a field-shift analysis of the measured resonances at the external field of 0.1, 0.2, 0.4, 0.6, and 0.8 T. The resonances for {sup 126}I{ital Fe} and {sup 130}I{ital Fe} were observed in an external magnetic field of 0.2 T at {nu}({sup 126}I{ital Fe})=627.7(2) MHz and {nu}({sup 130}I{ital Fe})=585.7(2) MHz, respectively. Using the recalculated hyperfine field of {ital B}{sub HF}({sup 131}I{ital Fe})=114.50(5) T, the magnetic moments were deduced: {vert bar}{mu}({sup 124}I,2{sup {minus}}){vert bar}=1.444(4){mu}{sub {ital N}}, {vert bar}{mu}({sup 126}I,2{sup {minus}}){vert bar}=1.436(5){mu}{sub {ital N}}, and {vert bar}{mu}({sup 130}I,5{sup +}){vert bar}=3.349(7){mu}{sub {ital N}}. The present value of the magnetic moment of {sup 124}I is very different from the value of 1.14(8){mu}{sub {ital N}} reported previously. The measured values of the magnetic moments are discussed using Lande formula.

Nuclear magnetic moments of the ground states of I 124 , I 126 , and I 130

The nuclear magnetic moments of {sup 124}I, {sup 126}I, and {sup 130}I have been measured by the techniques of low-temperature nuclear orientation and nuclear magnetic resonance on oriented nuclei. The magnetic hyperfine splitting frequency {vert bar}{ital g}{mu}{sub {ital N}BHF}/{ital h}{vert bar} for {sup 124}I{ital Fe} was determined to be 630.2(2) MHz from a field-shift analysis of the measured resonances at the external field of 0.1, 0.2, 0.4, 0.6, and 0.8 T. The resonances for {sup 126}I{ital Fe} and {sup 130}I{ital Fe} were observed in an external magnetic field of 0.2 T at {nu}({sup 126}I{ital Fe})=627.7(2) MHz and {nu}({sup 130}I{ital Fe})=585.7(2) MHz, respectively. Using the recalculated hyperfine field of {ital B}{sub HF}({sup 131}I{ital Fe})=114.50(5) T, the magnetic moments were deduced: {vert bar}{mu}({sup 124}I,2{sup {minus}}){vert bar}=1.444(4){mu}{sub {ital N}}, {vert bar}{mu}({sup 126}I,2{sup {minus}}){vert bar}=1.436(5){mu}{sub {ital N}}, and {vert bar}{mu}({sup 130}I,5{sup +}){vert bar}=3.349(7){mu}{sub {ital N}}. The present value of the magnetic moment of {sup 124}I is very different from the value of 1.14(8){mu}{sub {ital N}} reported previously. The measured values of the magnetic moments are discussed using Lande formula.