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The IAEA laboratories have access to both nuclear analytical methods and conventional instrumental methods for trace analysis for the characterisation of its environmental and biological reference materials. A technical concept integrating the homogeneity data, the recommended test portion mass and the uncertainty on the trace element concentrations is explored using a combination of INAA, XRF, ICP-MS, ICP-AES, and AAS. The above approach is illustrated by selected examples of reference materials currently under evaluation for their trace element content. They include some or all of the following elements Al, As, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Th, U, Zn in environmental biomonitor organisms (lichen, algae) and air dust filters.

About 250 sets of polycarbonate (Nuclepore, Costar) membrane filters loaded with two urban air particulate matter (APM) obtained in Vienna and Prague were prepared by filtration of a watter suspension of the above APM materials. The homogeneity of both bulk APM materials and the loaded filters was tested by determining a number of elements by instrumental neutron activation analysis (INAA), proton induced X-ray emission (PIXE) and micro-X-ray fluorescence (μ-XRF). Relative standard deviations due to inhomogeneity (sinh) were below 3% for many elements in the bulk APM materials. In the loaded filters, the sinh values increased significantly. Nevertheless, for up to 20 elements important in air pollution studies the sinh values were below 15%, allowing target values with a reasonably low uncertainties (up to 20%) to be derived for the future use of the filters in proficiency testing of laboratories involved in air pollution monitoring.

Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.

The γ-decay of the GDR in hot Hg and Eu isotopes has been measured in coincidence with selected low-energy γ-transitions of the evaporation residues. In the Hg case, the GDR width at finite temperature and at different spins was studied by analyzing simultaneously with the statistical model the high-energy γ-ray spectra associated with different residual nuclei and the fractions of residue cross-sections. The measured GDR width was found in good agreement with the predictions of the thermal fluctuations model. In the case of Eu, we have measured the high-energy γ-rays in coincidence with low-energy γ-transitions from different nuclear configurations of 143 Eu in order to search for the GDR decay built on a superdeformed state. The analysis of the data shows a possible evidence of this state. The measured intensity indicates that the superdeformation survives only few MeV above the yrast line.

The lifetime of the unresolved transitions forming the rotational quasi-continuum spectra has been measured in 163 Tm using the Doppler shift attenuation technique. Spectra associated to different values of the coincidence folds, angular anisotropies and the dynamical moment of inertia were also obtained from the present experiment. The Doppler shift has been measured for discrete transitions, for the ridge structures in E γ 1 × E γ 2 spectra and for the rotational E2 bump in one dimensional spectra. The data were compared to the theory using a simulation model which makes use of microscopically calculated levels and transition probabilities. Above 1300 keV the results indicate collectivity with lifetime faster than 10 −14 s, while at lower E γ the results are well described by predictions with B (E2) = 400 WU.

High-spin states in 177 W have been populated using the 164 Dy( 18 O,5n) reaction at a beam energy of 83 MeV. Six new high- K bands based on 3-, 5- and 7-quasiparticle excitations have been observed. Nilsson configurations for these bands are discussed, and experimental and calculated g -factors are compared. Decays of the K π = 29 2 + 5-quasiparticle state to the members of the K π = 7 2 + band have been observed. The decay rates are compared with predictions calculated within a tunneling model where the nuclear shapes are considered to change along the γ direction in the ( ϵ 2 , γ) deformation plane.

Using the (18O,5n) 163Er reaction a multitude of rotational bands have been established with firm spin and parity assignments in 163Er. In 17 out of 24 band crossings E2 cross-band transitions have been observed. The interaction strength varies between ∼ 1 and ∼ 50 keV with many of the values in the range 10–15 keV. These interactions sample a variety of the lowest (multi) -quasiparticle configurations. For some bands, in particular those with high K-values, the configurations can be established rather well. Quite complicated changes in the wavefunctions must occur at these crossings, and to explain the observed interaction strengths coupling to various vibrational degrees of freedom, in addition to possible residual neutron-proton interactions, may be needed.

High-energy γ-rays from the decay of the giant-dipole resonance (GDR) in the hot 106Sn compound nucleus and its daughters were measured in coincidence with heavy recoiling evaporation residues. The compound nucleus was formed at excitation energy E ∗ = 80 MeV using the reaction 56Ni+48Ti at a bombarding energy of 260 MeV. The analysis yields the GDR width for two different intervals of angular momentum 〈J〉 = 24 and 36ℏ. The present data, combined with previous data at higher angular momentum permit a study of the angular momentum dependence of the GDR width for 10 ⩽ J ⩽ 60ℏ at approximately fixed temperature. The width of the GDR is found to be roughly constant for J

The damping mechanisms of the giant dipole resonance at finite temperature T and rotational frequency ω are investigated by studying the GDR lineshape of 167 Er associated with a very narrow interval of excitation energy (of the order of 6 MeV) at T = 1.3 MeV. The strength function data can be reproduced either assuming collisional damping width equal to T = 0 and adiabatic thermal fluctuations or assuming a larger collisional damping without thermal fluctuations. The measurement of the angular distribution of the high energy gamma rays rules out the second possibility.

The high energy gamma decay of the GDR in rotating excited nuclei formed by heavy ion fusion reactions is studied.

Experimental investigations of the giant dipole resonance at finite temperature provide new insight into different properties of hot rotating nuclei. Here we discuss the studies aiming at the understanding of the role of thermal and quantal fluctuations in the measured GDR width. We also present the first studies of the properties of super-heavy nuclei through the γ-decay of the GDR in the hot compound prior to fission.

The response of a HPGe (82%) detector with a BGO anti-Compton shield has been studied for the 15.1 MeV γ-rays produced by the reaction D( 11 B,nγ) 12 C and for the 6.13 MeV γ-rays produced by a 238 Pu 13 C source. The energy deposited in the HPGe and in the BGO was measured for each detected γ-ray. The sum energy and the spectra of the HPGe in anticoincidence with the BGO were obtained and compared to simulated spectra calculated with the GEANT libraries. The measured energy resolution for the 15.1 MeV γ-rays emitted by 12 C is 209 keV. Due to the velocity ( β = 0.05) of 12 C, the Doppler broadening contribution to the measured FWHM is 140 keV. For the 6.13 MeV γ-rays emitted by the 238 Pu 13 C source, the measured energy resolution was 132 keV.

A study of the strength function and of the angular distribution of the gamma rays from the giant dipole resonance in hot rotating Sn nuclei is presented. The two GDR observables (spectrum and angular distribution) were measured at the nuclear temperature T ∼ 2 MeV for several different angular momentum intervals of the compound nucleus. The data were obtained with the HECTOR detector array that includes a 38 element multiplicity filter. Data are compared to model predictions of adiabatic thermal fluctuations of shape and orientation angles. A satisfactory agreement is found with the exception of the angular anisotropy at the higher rotational frequencies. The systematics of angular momentum dependence of the GDR width and of the a 2 ( E γ ) suggests a constant spreading width at this temperature.

High-energy $\ensuremath{\gamma}$ rays emitted by the decay of the hot compound nucleus ${}^{194}\mathrm{Hg}$, formed in the reaction ${}^{30}\mathrm{Si}(142 \mathrm{MeV}{)+}^{164}\mathrm{Dy}$, have been measured in coincidence with different residual nuclei. The measured spectra and the relative residual-nucleus cross sections were simultaneously analyzed with the statistical model. Calculations assuming contributions from a GDR in superdeformed states were also made. No clear evidence was found that superdeformed shapes seen at $T=0$ survive at average nuclear temperature $〈T〉\ensuremath{\simeq}1.3 \mathrm{MeV}$. Instead, an average nuclear deformation corresponding to $〈\ensuremath{\beta}〉=0.3$ constant with spin has been deduced for $20lIl38 \ensuremath{\Elzxh}$ by comparing the measured width to that predicted by the model of thermal shape fluctuations.

The \ensuremath{\gamma} cascades feeding into low-K and high-K bands in ${}^{163}$Er are investigated analyzing variances and covariance of the spectrum fluctuations. From a large data set of 1${0}^{9}$ triple coincidences, \ensuremath{\gamma}-\ensuremath{\gamma} coincidence spectra gated by resolved low-lying rotational bands are analyzed. Low-K bands are found to be fed by a much larger effective number of cascades than high-K bands. The covariance between pairs of gated spectra shows that the cascades feeding low-K bands are different from those feeding the high-K bands. The persistence of the K-selection rules for the excited rotational bands within the angular momentum region $30\ensuremath{\Elzxh}\ensuremath{\le}I\ensuremath{\le}40\ensuremath{\Elzxh}$ is suggested as explanation.

The strength function and the angular distribution of the high energy {gamma} rays emitted by the giant dipole resonance (GDR) in hot rotating{sup 109,110}Sn nuclei have been measured at temperature {ital T}=1.8 MeV and at four values of the angular momentum {ital I}. The GDR width is {approx}2 times larger than at {ital T}=0 and increases by {approx}20% as {ital I} goes from 40 to 54{h_bar}. The {ital a}{sub 2}({ital E}{sub {gamma}}) increases by a factor of {approx}2. Based on these two facts and on the comparison with theory we conclude that large deformations driven by {ital I} and combined with shape and orientation fluctuations are responsible for the measured increases. Collisional damping is constant and practically equal to the {ital T}=0 case.

A search for the γ decay of the Giant Dipole Resonance built on superdeformed (SD) nuclear configurations of 143Eu was made, using the reaction 110Pd(37Cl, 4n)143Eu at 165 MeV. Eight large BaF 2 scintillators and the NORDBALL array were used to measure high and low-energy γ-rays. The γ-spectrum gated by transitions populated by the SD states shows an excess yield at 7-10 MeV compared to the spectrum gated by transitions not populated by SD states. The comparison with statistical model predictions indicates that this excess most probably is due to γ-ray emission of the GDR built on superdeformed states.

Several of the known rotational bands in 164Er are extended considerably (to around 35 h). In addition, a new coupled band is established and found to decay by an isomeric transition with t1/2 ≥ 170 nsec, to the 11t - state of the known Kπ =7− two-quasi-proton band. The new band is interpreted as a four-quasi-particle structure, with measured values of B(M1)/B(E2) consistent with the configuration [7t -] ⊗ ?i13/2[642 5/2+] ⊗ ?h9/2[523 5/2t -], i.e. [7t -]⊗ [AE,AF]. This is supported by the observation of a crossing which resembles the second i13/2 neutron crossing, BC, associated with the two-quasi-neutron band built on the configuration, [AE,AF]. The routhian of the new band is close to the sum of the individual routhians of [AE,AF] and [7−]. The cause of a small gain in energy of 130–272 keV is discussed.

The γ-decay of the Giant Dipole Resonance (GDR) built on excited nuclear states has been measured for the nucleus143Eu. The reaction110Pd(37Cl, 4n)143Eu at a beam energy of 165 MeV has been employed. This experiment aimed at searching the γ-decay of the GDR built on the superdeformed143Eu states, populated at high spins. High-energy γ-rays were detected in 8 large BaF2 scintillators in coincidence with discrete transitions measured with the NORDBALL array (in the configuration consisting of 17 HPGe detectors and a 2π multiplicity filter). The spectrum of high-energy γ-rays gated by low-energy transitions between states fed by the superdeformed states shows some excess of yield in the 7–10 MeV region with respect to that gated by transitions between states not populated by the superdeformed states. This excess should be due to the γ-decay of the the giant dipole oscillation along the superdeformed axis of the nucleus that is expected to have a frequency corresponding to ≈9–10 MeV (low-energy component of the GDR strength function). The measured excess, in spite of the large error bars, is found to be of the same order as predicted statistical model values.

The γ-decay of the Giant Dipole Resonance in hot rotating compound nuclei has provided valuable information on the nuclear structure at finite temperature. A number of experimental results showing that the nuclear shapes change with temperature and angular momentum are here reviewed. In particular we concentrate on the temperature interval from 1 to 2 MeV, rotational frequencies from 0.2 to 1.5 MeV and on nuclei in the mass regionsA≈160–170 andA≈110, characterized by the prolate-oblate and spherical-oblate phase transitions, respectively. The possibility to study the shapes involved in the compound nucleus formation is also discussed. For this purpose long formation times are required and the nucleus170W formed with the reaction60Ni+110Pd, here studied, seems to be a good candidate. The gamma and particle decays were compared to those of the reaction48Ti+122Te. The comparison shows that in average the energy of the α-particles is larger for the more symmetric reaction, consistent with longer formation times and larger deformations in the pre-equilibrium stage.