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The positron spectrum of Cu61 has been examined recently by Cook and Langer with a large magnetic spectrometer. The experimental curves of these authors show a deviation from the Fermi distribution which is much larger than for Cu64 and it seems possible that not all of this deviation arises from the instrumental factors. It is pointed out by different authors that Cu61 does not emit nuclear gamma-rays which means that the spectrum of Cu61 must be simple. On the other hand the measurements of Cook and Langer can hardly be understood without the assumption of a complex spectrum. To examine this discrepancy, we started a search for gamma-radiation in Cu61.

A study has been made of the gamma radiation following the decay of Ir192. The energies, intensities, internal conversion coefficients and multipolarities of the gamma transitions have been determined. Energy level schemes for the daughter nuclei, Pt192 and Os192, are proposed. The spins and parities of most of the levels are given.

The beta - decays of Ta182 and Ta183 into excited states of W182 and W183 have been studied using a curved crystal gamma-ray diffraction spectrometer and a homogeneous field, ring focusing beta-ray spectrometer. In each case de-excitation of the daughter nucleus gives rise to complex gamma-ray and conversion electron spectra. Energies and relative intensities of gamma rays and conversion lines arising from 27 transitions in W182 and 29 transitions in W183 are presented. Internal conversion coefficients and multipolarities have been deduced for most of the transitions and together with the gamma-ray energies form the basis of decay schemes proposed for both W182 and W183. The two decays are reported together because of the close experimental relationship which existed between them as a consequence of the method used for their production, namely, simultaneous production of Ta182 by single neutron capture and Ta183 by double neutron capture from stable Ta181. A corollary result is the value 1.3 x 10^4 barns for the thermal neutron cross section of Ta182. An interpretation of these results on W182 in terms of collective rotational motion has been given by A. Bohr and collaborators [Kgl. Danske Videnscab. Selskab, Mat.-fys. Medd. 29, No. 9 (1955)].

The nuclear levels of Ta181 were investigated by a study of the β decay of Hf181 and the electron capture decay of W181. Evidence for weak M-shell conversion lines of an ∼6-kev transition in the Hf181 was found with a β spectrometer. An investigation of the W181 decay with this instrument revealed strong M-shell conversion lines corresponding to a 6.25±0.3-kev transition. With the aid of additional evidence, the conclusion is made that the 476-kev transition in the Hf181 decay occurs between the 482-kev level and a new level at 6 kev. On using an argon proportional counter, a 6-kev γ ray was also found in the W181 decay. The conversion coefficient of this transition was determined to be αT=44±7. This conversion coefficient and the M-subshell conversion ratios indicate that the 6-kev transition is of E1 multipolarity. The 6-kev level is assigned as the 9/2- [514] Nilsson intrinsic state. It is also concluded that the previously reported 152-kev transition in the W181 decay occurs between a new 11/2- (K=9/2-) rotational level at 158 kev and the 6-kev level. From a measurement of the tantalum L/K x-ray intensity ratio, the W181 decay energy is found to be 176-22+44 kev. The branchings of this decay to the various Ta181 levels are as follows: 158 kev (0.11%), 136 kev (0.067%), 6.25 kev (∼35%), and ground state (∼65%). All findings and proposals are consistent with predictions of the unified model of the nucleus.

[No abstract.]

Investigations of the decay of the three-particle state in Lu177 with spin 23/2- performed with the crystal diffraction technique revealed evidence for three-particle states in Hf177 and rotational bands in Lu177 and in Hf177. Levels with spins to 17/2 were found in the K=7/2+ rotational band in Lu177 while the K=7/2- and K=9/2+ bands in Hf177 were found to be excited up to spin 21/2 levels. From energy and intensity measurements of the cascade, crossover, and interband transitions, the values of a number of parameters pertinent to the collective model were derived. In particular, it was verified for each of the rotational bands that the quantity (gK-gR)/Q0 was a constant within the experimental error.

The absolute yield of the Mössbauer absorption of the 8.42-keV transition in Tm169 was determined for a thulium oxide and a thulium metal absorber. The 8.42-keV gamma ray was resolved from the L x rays of erbium by means of a flat lithium fluoride crystal diffraction spectrometer. From the observed Mössbauer absorption effect the total conversion coefficient αtot=325±35 and the magnetic transition rate of B(M1, 3/2→1/2)=5.1×10^-2 (eh/2Mc)^2 was derived.

It has been proposed by Gell-Mann(1) that the usual vector interaction in beta decay should be modified by addition of a small correction term due to the effect of virtual meson currents around the nucleons. This term in proportional to the difference of the anomalous magnetic moments of protons and neutrons and is of the order of 0.1% per Mev beta energy.

The energies and relative intensities of the gamma radiation and the relative intensities of the conversion electrons following the decay of 5.5-hr Hf180m have been measured using the curved-crystal gamma-ray spectrometer (recently calibrated for accurate intensity measurements), the ring-focused beta-ray spectrometer, and the semicircular spectrometer at the California Institute of Technology. The measured transition energies are: 57.54±0.01, 93.33±0.02, 215.25±0.13, 332.5±0.3, and 443.8±0.6 kev. The energy levels deduced from these values are not entirely consistent with the two-parameter rotational formula. Conversion coefficients derived from the measurements were absolutely normalized using a method involving information available from the decay scheme. All of the 57.54-kev transition conversion coefficients are anomalously high if compared with the theoretical E1 coefficients. No admixture of M2+E3 can account for the anomaly. The K conversion coefficients of the E2 transitions are all about 10% low with exception of the 93.33-kev transition. The L coefficients have a varying deviation, the maximum being 12%. The K conversion coefficient of the 501.3-kev transition has the value 0.037±0.012 which is consistent with the theoretical E3 value of 0.040.

The study of β-γ circular polarization correlation in β transitions without spin change provides valuable information about β-decay coupling constants. (1,2) In particular, the experimental result will depend on the presence or absence of S,T and V,A interference terms.(2)

The energy shifts of Kα2, Kα1, Kβ3, Kβ1, and Kβ2 x rays were measured for the following Ru, Pr, and Yb compounds: Ru, Ru(CO2)Cl2, RuO2, [Ru(NH3)4OHCl]Cl · 2H2O, and RuF3; Pr, PrC2, Pr2O3, PrFeO3, Pr6O11, PrO2, CsPrF5, and Cs2PrF6, Yb, YbF3, and Yb2O3. The results are compared with free-ion relativistic self-consistent-field calculations. The measurements bear out the dominant role of the 4f electrons in energy shifts between the trivalent and tetravalent Pr and the divalent and trivalent Yb. In Yb the full free-ion value is observed, while in Pr the free-ion value appears to be attenuated by a factor of 0.4, presumably owing to covalency. In all cases the relation of the x-ray energy shift to the Mössbauer isomer shift is discussed.

[No abstract].

The electron and gamma-spectra from RaD and RaE have been thoroughly investigated. The gamma-radiation from RaD was studied with both krypton and argon proportional counters with brass and aluminum cathodes. The L alpha, L beta, and L gamma radiations of Bi were observed and identified with a critical absorber. The intensity ratios of L alpha:L beta:L gamma are 1:1:0.2. The previously reported 7.8-kev (10 percent) line was not found but could be strongly excited by copper backing. The weak 23-kev line (10^-3 per disintegration in our measurements) could be contributed from the piling effect of the detecting system. The conversion electrons of RaD were investigated in a solenoid magnetic spectrometer to obtain the L and (M+N) conversion coefficients. The results are: NeL / N beta =64 percent, NeM+N / N beta =21 percent, NeL+M+N / N beta =(85±5) percent. The conversion electrons of RaD were again investigated with a 180° beta-spectrometer with a resolution of 0.8 percent and a counter window of ~6 µg/cm2. The LI, LII, and LIII conversion lines of the 46.5-kev gamma-ray were resolved. The ratio of LI:LII:LIII:MI-III:MIV-V:NI-V:NVI-VIII+0 are 1:0.075:0.007: 0.25:0.006:0.07:0.007. From the ratios of the L-subshell conversion electrons, the 46.5-kev transition is interpreted as an M1 type. The upper limit of the intensity of the reported lines at 42 kev, at 37 kev, and at 31 kev must be less than 0.5 percent per disintegration if the same conversion coefficient is assumed. The unconverted 46.5-kev gamma-radiation is 0.07±0.02 per disintegration. Thus the excited state of 46.5 kev in RaE can account for (92±5) percent of the disintegrations. Neither internal conversion electrons nor nuclear gamma-radiations are found in RaE. A faint x-ray (~80 kev) of the order of 10-4 per disintegration due to the ionization effect was observed in RaE. A brief discussion of the decay scheme of RaD and the possible spin assignments of various levels is included.

Nuclear levels in Tm169 excited by electron capture of Yb169, and levels in Lu175 excited by both beta decay of Yb175 and electron capture of Hf175 have been studied by using the curved-crystal gamma-ray spectrometer and the ring-focusing beta-ray spectrometer, as well as a semicircular beta-ray spectrometer for low energies. From the precision energies and the multipolarity determinations, the levels in Tm169 have the following energies in kev, and spin and parity assignments: A (ground state) (½+), B 8.42 (3/2+), C 118.20 (5/2+), D 138.95 (7/2+), E 316.19 (7/2+), F 379.31 (7/2-), G 472.91 (9/2-). Levels A, B, C, and D are members of a rotational band whose characteristic constants are given. Levels E and F are interpreted as particle excitations and level G as a rotational level based on the state F. The Lu175 excited states have the following energies in kev, spins, and parities: A (ground state) (7/2+), B 113.81 (9/2+), C 251.46 (11/2+), D 343.40 (5/2+), E 396.31 (9/2-), F 432.76 (7/2+), G 504.7 (1/2+). A, B, and C form a rotational band for which the characteristic constants are given. Some features of the levels and transition probabilities are discussed and compared with the unified model. A brief survey of second-order rotational energy constants and of intrinsic excitation levels is given.

The existence of a strong interference between the Gamow-Teller and the Fermi part of the β interaction has been reported from this laboratory(1,2) in a study of the circular polarization of the γ rays measured in coincidence with the preceding β particles(3) in the case of Sc46.

In the beta-decay of N16 to the 1- (7.1-Mev) and 3- (6.1-Mev) excited states of O16, respectively, a discrepancy exists between the branching ratio of about 1:1 determined from absorption measurements on the beta-spectrum, and the ratio of about 1:12 from measurement of the associated gamma-ray intensities. If both measurements are to be reconciled, the most likely possibility is a strong E2 gamma-ray transition from the 7.1-Mev to the 6.1-Mev level. The likelihood that this E2could give serious competition to the normal 7.1-Mev E1 ground state transition is enhanced by the isotopic spin selection rule forbidding E1 transitions with [delta]T = N - Z = 0. In order to explain the quantitative discrepancy in this way, however, this selection rule would have to be much stronger than suggested by simple estimates.

The β-γ circular polarization correlation provides a valuable tool for the study of the beta-decay interaction.(1,2) Recently a large interference term due to the presence of S and T or V and A interaction has been found in the allowed J-J transition of Sc46.(3) We report here studies of the J-J transitions in Au198 and Co58.

The gamma rays emitted from Tm171 following the Er171 beta decay have been measured with the twometer curved-crystal spectrometer and a semicircular beta-ray spectrometer, enabling a comparison of the nuclear levels and rotational parameters for the Tm171 ground-state band with the corresponding levels and parameters of Tm169. The measured gamma rays have the following energies in kev: 5.06±0.05, 12.40±0.05, 111.63±0.02, 116.69±0.03, 124.03±0.03, 210.62±0.15, 284.9±0.7, 295.97±0.15, 308.37±0.15. In comparing the rotational parameters, a slight increase in the deformation of Tm171 over that of Tm169 is noted. The relatively large change in the decoupling parameter (a=-0.8563) for Tm171 compared with that of Tm169 cannot be accounted for entirely by the small change in nuclear deformation.

The circular polarization of the 265-kev γ rays following the mixed Gamow-Teller and Fermi electron-capture decay of Se75 into As75 has been measured. The neutrino momentum was fixed with the help of a resonance scattering process. From the experimentally determined degree of right-hand circular polarization of -0.21±0.15 it was concluded that the sign of the Gamow-Teller to Fermi matrix-element ratio in this beta decay is negative.

The nuclear spectrum of Ta181 has been investigated. The excited levels have energies of 136.25, 482.0, 615.0, 618.9, and 958.0 kev. The gamma-ray energies are 3.9, 133.02, 136.25, 136.86, 345.85, 476.0, 482.0, and 615.5 kev. Multipolarities for the gamma rays are given and spin assignments to the levels are proposed.

The nuclear spectrum of Lu177 has been investigated. Three excited levels of Hf177 have energies of 112.97 kev, 249.69 kev, and 321.33 kev. A decay scheme is proposed.

The analysis and results are presented from the complete data set recorded at Palo Verde between September 1998 and July 2000. In the experiment, the $\nuebar$ interaction rate has been measured at a distance of 750 and 890 m from the reactors of the Palo Verde Nuclear Generating Station for a total of 350 days, including 108 days with one of the three reactors off for refueling. Backgrounds were determined by (a) the $swap$ technique based on the difference between signal and background under reversal of the positron and neutron parts of the correlated event and (b) making use of the conventional reactor-on and reactor-off cycles. There is no evidence for neutrino oscillation and the mode $\nuebar\to\bar��_x$ was excluded at 90% CL for $\dm>1.1\times10^{-3}$ eV$^2$ at full mixing, and $\sinq>0.17$ at large $\dm$., 11 pages, 8 figures

At Elan Bank of the Kerguelen Plateau in the southeast Indian Ocean, Leg 183 of the Ocean Drilling Program recovered clasts of garnet-biotite gneiss in a fluvial conglomerate intercalated with basalt flows. U-Pb and Pb-Pb dates of zircons and monazites in these clasts and an overlying sandstone range from 534 to 2547 Ma, which is much older than the surrounding Indian Ocean seafloor. These dates show that old continental crust resides in the shallow crust of the oceanic Kerguelen Plateau and that the breakup of Gondwana dispersed continental fragments into the nascent Indian Ocean lithosphere.