Lifetimes of 160 different spin-splitted rotational levels of the OD A ' z + state (v = 0-3) have been measured at high spectral resolution using the High Frequency Deflection technique. From these data the variation of the electronic transition moment is deduced as well as the predissociation rates for levels above the dissociation limit. These rates are compared to calculated ones based upon spin-orbit coupling between the crossing 'E+ and 4 Z -states. From a least square fit to the predissociation rates a potential crossing point slightly above v = 5 of the A state at r = 1.50 i 0 . 0 2 8 , and a spin-rbit coupling element H,, = 36 f 18 cm-' are found.

No abstract

No abstract

A search for high-spin isomeric states in the 138,139Ce anc 141,142Nd nuclei has been made using (α, xn) reactions and the intrinsic pulsing of the 225-cm Stockholm cyclotron. In 138Ce, besides the known 7- isomeric state at 2 128.8 keV, another one at 3 538.5 keV, 10+, with T 1/2 = (78 ± 5) ns has been found. In 139Ce a new isomeric state at 2 631.5 keV, 19/2-, with T 1/2 = (70 ± 5) ns has been identified. Also in 141Nd a high-spin isomeric level exists probably at 3 104.9 keV with T 1/2 = (26 ± 5) ns. In 142Nd the level at 3 453.0 keV, with spin I = 6, shows a half-life T 1/2 = (1.3 ± 0.1) ns while that at 4 718.5 keV, I = 8, decays with a half-life of about 0.8 ns. The time distributions in 142Nd show that the 3 242.9 keV, I = 7, or the 3 456.2 keV, I = 8, level is also delayed and decays with T 1/2 = (1.6 ± 0.1) ns. The deduced transition probabilities are compared to theoretical predictions.

Abstract. The studies aimed at determining low activities of alpha radioactive elements are widely recognized as essential for the human health, because of their high radiotoxicity in case of internal contamination. Some groups of workers of nuclear facility at Otwock are potentially exposed to contamination with plutonium isotopes. For this reason, the method for determination of plutonium isotopes has been introduced and validated in Radiation Protection Measurements Laboratory (LPD) of the National Centre for Nuclear Research (NCBJ). In this method the plutonium is isolated from a sample by coprecipitation with phosphates and separated on a AG 1-X2 Resin. After electrodeposition, the sample is measured by alpha spectrometry. Validation was performed in order to assess parameters such as: selectivity, accuracy (trueness and precision) and linearity of the method. The results of plutonium determination in urine samples of persons potentially exposed to internal contamination are presented in this work.