[en] The β⁺/EC decay of a mass-separated ⁸⁰Y source has been studied by β- and γ-ray spectroscopy following the bombardment of a thin ²⁴Mg target with ⁵⁸Ni ions at 190 MeV. An extended decay scheme with 14 new states in ⁸⁰Sr has been identified including the first observation of negative-parity states. The low-lying positive-parity states have been found to be clustered indicating a pattern of one-, two-, and possibly three-phonon multiplets characteristic of an anharmonic vibrator. Some states in ⁸⁰Sr can also be grouped into a γ-vibrational band. In general the low-lying states in light strontium isotopes show vibrationlike collectivity which evolves to rotational behavior with increasing spin and decreasing neutron number. The observed ⁸⁰Yβ-decay fragmentation and log ft values have also been used to assign spin and parity of 4^- and 1^- to the parent ground state and the 228.5 keV isomeric state, respectively. copyright 1999 The American Physical Society

[en] Direct mass measurements of A=80 isobars were performed using the second cyclotron of SARA (systeme accelerateur rhone-alpes) of the ISN (institut des sciences nucleaires) in Grenoble as a time-of-flight mass spectrometer. Using the 300 MeV ⁵⁸Ni+²⁷Al reaction, the isobars ⁸⁰Rb,⁸⁰Sr,⁸⁰Y, and ⁸⁰Zr (only one event.) were measured. For ⁸⁰Y we found a mass value of 79.934320(180) u, corresponding to a decay energy Q (⁸⁰Y→⁸⁰Sr) of (9120± 170) keV. Comparing this value to the former experiments of Lister et al. and Della Negra et al. results in a difference of about 2.2 MeV. However, it does agree with the recommended value of Audi and Wapstra, which is derived from systematic trends. For ⁸⁰Zr the single event was identified with a probability of 0.999975 and a mass value of 79.940400(1600) u could be deduced from our experiment. (orig.)

[en] The HIGISOL facility has been used to investigate carefully the isomeric transition 228.5 keV in ⁸⁰Y. We have measured the electron internal conversion coefficient for this transition α_K=0.50±0.07 which gives the value for half-life of ''bare'' isomeric state T_1/2=6.8±0.5 s. The isomeric state should play an important role in the rp-process calculations. (orig.)

[en] The masses of neutron-deficient nuclides near the N=Z line with A=64-80 have been determined using a direct time-of-flight technique which employed a cyclotron as a high-resolution spectrometer. The measured atomic masses for ⁶⁸Se and ⁸⁰Y were 67.9421(3) u and 79.9344(2) u, respectively. The new values agree with the 2003 Atomic Mass Evaluation. The result for ⁶⁸Se confirms that this nucleus is a waiting point of the rp-process, and that for ⁸⁰Y resolves the conflict between earlier measurements. Using the present results and the 2003 Atomic Mass Evaluation compilation, the empirical interaction between the last proton and the last neutron in N=Z nuclei has been revisited and extended

[en] The masses of ten neutron-deficient nuclides near the N = Z line with A 64-80 have been measured with the direct time-of-flight technique using the CSS2 cyclotron as a high-resolution spectrometer. All measured masses agree with the 2003 atomic mass evaluation and are compared to the predictions of the finite range droplet model. The atomic mass excesses obtained for ⁶⁸Se and ⁸⁰Y are -53.958(246) MeV and -60.971(180) MeV, respectively. The new results for ⁶⁸Se and ⁸⁰Y are compared to other recent experimental values

[en] Beta decay end point energies of the T_z=1 odd-odd nuclei, ⁸⁰Y, ⁸⁴Nb, ⁸⁸Tc were measured by using βγ-coincidences. The Q_EC-values were deduced to be 6.2 ± 0.6, 7.2 ± 0.3 and 7.8 ± 0.6 MeV for ⁸⁰Y, ⁸⁴Nb and ⁸⁸Tc, respectively. These values are more than 2 MeV lower than those predicted by most of the mass formulae. It is suggested that these anomalies may be partly attributed to residual p-n interactions of odd-odd nuclei. (author)

[en] The Q_EC value of ⁸⁰Y has been measured by β-γ coincidence spectroscopy to be ≥8929(83) keV. Combining this result with the adopted mass excess of the daughter ⁸⁰Sr gives a mass excess for ⁸⁰Y of ≥-61 376(83) keV. Results are compared with other measurements, with Audi-Wapstra systematics, and with predictions of mass formulas. Implications of this measurement are considered for the rp process

[en] Fragmentation products from a ⁹²Mo beam on a natural nickel target have been used to study structural properties of the very neutron deficient nuclei around N∼Z∼40. We present the first observation of isomeric decays in the T_Z=1 systems ⁷⁴Kr, ⁸⁰Y and ⁸⁴Nb. The isomer in ⁷⁴Kr is interpreted as the hindered decay from an excited 0⁺ state, confirming the prediction of prolate/oblate shape coexistence in this nucleus. Transitions from states below an isomer in the N=Z nucleus ⁸⁶Tc have also been tentatively identified, making this the heaviest N=Z system for which decays from excited states have been observed. In addition, we have obtained the first conclusive evidence for the existence of the T_Z=1/2 isotopes ⁷⁷Y, ⁷⁹Zr and ⁸³Mo. The data for ⁷⁷Y is of particular interest in light of the reported instability in the lighter odd-Z, T_Z =-1/2 systems ⁶⁹Br and ⁷³Rb. (author)

[en] This paper presents two original direct mass-measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high-resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time-of-flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are -53.958(246) MeV and -60.971(180) MeV, respectively. The new mass-measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio-frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass-measurement method and to understand the systematic errors

[en] The results of the measurement of the Q-value for the beta-plus decay of Sr-79, Y-80 and Y-82 are reported. The nuclei were formed in heavy ion reactions. The experimental aparatus is described. Results are compared to model predictions