Search results for "Isotopes of thorium"

Resonance ionization spectroscopy of thorium isotopestowards a laser spectroscopic identification of the low-lying 7.6 eV isomer of 229Th

2011

International audience; In-source resonance ionization spectroscopy was used to identify an efficient and selective three step excitation/ionization scheme of thorium, suitable for titanium:sapphire (Ti:sa) lasers. The measurements were carried out in preparation of laser spectroscopic investigations for an identification of the low-lying 229 m Th isomer predicted at 7.6 ± 0.5 eV above the nuclear ground state. Using a sample of 232 Th, a multitude of optical transitions leading to over 20 previously unknown intermediate states of even parity as well as numerous high-lying odd parity auto-ionizing states were identified. Level energies were determined with an accuracy of 0.06 cm −1 for inte…

Isomeric Yield Ratios of 134I and 136I and Independent Fractional Yields of some Halogen Isotopes in the Fission of 232Th with Reactor Neutrons

1990

Mass mapping of a new area of neutron-deficient suburanium nuclides

2002

Abstract The masses of 64 short-lived neutron-deficient nuclides covering the element range from tungsten to uranium have been obtained for the first time. They have been evaluated by combining directly measured masses from Schottky mass spectrometry with linked experimental Q-values in α-decay chains. Based on these new mass data we have determined the one-proton and two-proton drip-lines as well as the size of the “littoral shallow” of the sea of instability. No evidence of a Thomas–Ehrman shift has been found in the region of the investigated heavy nuclides. A peculiar behavior of two-proton separation energies has been observed in the lead region. The predictive power of various mass mo…

Heavy isotopes of actinium: 229Ac, 230Ac, 231Ac and 232Ac

1973

Abstract By irradiation of 232Th with 150-MeV bremsstrahlung and with 14-MeV neutrons, three new neutron-rich isotopes of actinium, 230Ac, 231Ac and 232Ac, were produced and identified and the previously reported isotope, 229Ac, was confirmed. The actinium isotopes were chemically isolated by a fast procedure based on elution with α-hydroxyisobutyric acid from cation exchange resins. For 229Ac, a half-life of 62·7 ± 0·5 min and a β-ray energy of 1·14 ± 0·15 MeV were found; 35 γ-rays were observed, the strongest ones with the following energies and relative intensities: 135·3(34), 146·4(35), 164·6(100), 252·2(24), 261·9(39), 317·0(23), 539·9(20), 569·1(91), and 605·2 keV(23). For 230Ac, a ha…

Spectroscopy of Rn, Ra and Th isotopes using multi-nucleon transfer reactions

1999

Abstract High-spin spectroscopy of Rn, Ra and Th isotopes has been performed. The nuclei have been populated using multi-nucleon transfer reactions involving a 232 Th target and a 136 Xe projectile. This type of reaction offers the only mechanism for populating high-spin states in many of these nuclei. Interleaving bands with opposite parities have been observed to high spin ( ∼28 h ) in 218,220,222 Rn, 222,224,226,228 Ra and 228,230,234 Th. A systematic study of the rotational alignment properties of octupole bands in radon, radium and thorium isotopes reveals information concerning the role of the octupole phonon and the onset of stable octupole deformation with increasing rotational freq…

Excited states in neutron deficient even-even thorium isotopes (218?A?222)

1985

The nuclei218, 220, 222Th were investigated by conversion electron andγ-ray spectroscopy after compound nucleus reactions of14N with209Bi and16, 18O with208Pb. The intenseγ-background from fission was suppressed by spectroscopy of conversion electrons andγ-rays in coincidence with the evaporation residues or theirα-decay. Level schemes were determined for218Th up toIπ=10+ and for220Th and222Th up toIπ=15−. The observed structure of218Th may be explained in the spherical shell model with residual interaction by two neutron excitation. ForN≧130 completely different level schemes are observed showing very intense, collective electric dipole transitions (B(E1)−10−2 W.u.) with energies of typica…

Spectroscopic study of228-234Th nuclei using multi-nucleon transfer reactions

1999

Light-actinide nuclei in the octupole deformed region have been populated using multi-nucleon transfer from Th. The energy level schemes of several thorium isotopes with A = 228-234 have been extended up to and negative parity states have been observed for the first time in Th. A systematic study of the difference in alignment between the positive- and negative-parity bands in thorium nuclei in this mass region shows that Th behave like octupole vibrators, in contrast with Th, which are octupole-deformed in character. An intrinsic electric dipole moment has been measured for the first time in Th. The small value obtained is consistent with the vibrational description of this nucleus.

Production and characterization of a custom-made 228Th source with reduced neutron source strength for the Borexino experiment

2012

A custom-made 228Th source of several MBq activity was produced for the Borexino experiment for studying the external background of the detector. The aim was to reduce the unwanted neutron emission produced via (alpha,n) reactions in ceramics used typically for commercial 228Th sources. For this purpose a ThCl4 solution was converted chemically into ThO2 and embedded into a gold foil. The paper describes the production and the characterization of the custom-made source by means of gamma-activity, dose rate and neutron source strength measurements. From gamma-spectroscopic measurements it was deduced that the activity transfer from the initial solution to the final source was >91% (at 68%…