Pupils´interest in chemistry

Empirická studie zprostředkuje výsledky šíře koncipovaného výzkumu. Jedním z jeho cílů bylo zjistit míru zájmu žáků o učební předmět chemie na základní škole, vyhodnotit přispění chemie k přípravě žáků na život, k obohacení jejich poznání a využití osvojených vědomostí a dovedností v budoucím povolání. Studie sleduje též ve zkoumaných otázkách rozdíly mezi pohlavími. Popisuje dále vztahy mezi různými aspekty vyučování a mírou zájmu žáků o učební předmět chemie.This paper summarises the results of an empirical research project that aimed to examine elementary school pupils’ interests in Chemistry, pupils’ evaluation of benefits of Chemistry for their preparing for life, enrichment of their knowledge, and application of knowledge and skills in their future jobs. The study deals with gender differences in the examined questions. It also describes the relations between different aspects of teaching and intensity of interest in Chemistry

Quasiparticle random phase approximation with inclusion of the Pauli exclusion principle

Limitations of the Quasiparticle Random Phase Approximation (QRPA) are studied within an exactly solvable model, with a two body interaction of Fermi type. A special attention is paid to the violation of the Pauli exclusion principle (PEP) in solving the QRPA equation. A comparison of the exact solution, obtained by the diagonalization of a schematic nuclear Hamiltonian and those obtained within the standard QRPA, the renormalized QRPA, the QRPA with pertubative treatment of the PEP and the QRPA with exact consideration of the PEP, is presented. The agreement quality is judged in terms of the quasiparticle number operator matrix elements in the ground state and in the first excited states, of the beta transition amplitudes, of the Ikeda sum rule and of the nuclear matrix element for the double beta decay. We have found that restoring the PEP, the QRPA solutions are considerably stabilized and a better agreement with the exact solution is obtained.Comment: Revtex (preprint style), 23 pages, 7 postscript figures, typos added, references added, resubmitted to Phys. Rev.

Non-collapsing renormalized QRPA with proton-neutron pairing for neutrinoless double beta decay

Using the renormalized quasiparticle random phase approximation (RQRPA), we calculate the light neutrino mass mediated mode of neutrinoless double beta decay of Ge76, Mo100, Te128 and Te130. Our results indicate that the simple quasiboson approximation is not good enough to study the neutrinoless double beta decay, because its solutions collapse for physical values of g_pp. We find that extension of the Hilbert space and inclusion of the Pauli Principle in the QRPA with proton-neutron pairing, allows us to extend our calculations beyond the point of collapse, for physical values of the nuclear force strength. As a consequence one might be able to extract more accurate values on the effective neutrino mass by using the best available experimental limits on the half-life of neutrinoless double beta decay.Comment: 15 pages, RevTex, 2 Postscript figures, to appear in Phys. Lett.

Changes in mean-squared charge radii and magnetic moments of Tl 179-184 measured by in-source laser spectroscopy

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron-deficient isotopes Tl179-184 using the 276.9-nm transition. The experiment has been performed at the CERN-Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in Tl179,181,183 have been determined as I=1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in Tl182,184 from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes Tl179-184 follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of Tl183,184 has been observed, suggesting a larger deformation for the intruder-based 9/2- and 10- states compared to the ground states. An unexpected growth of the isomer shift for Tl183 has been found

Detailed α-decay study of 180Tl

International audienceA detailed $\alpha$-decay spectroscopy study of $^{180}\mathrm{Tl}$ has been performed at ISOLDE (CERN). $Z$-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of $^{180}\mathrm{Tl}$. Fine-structure $\alpha$ decays to excited levels in the daughter $^{176}\mathrm{Au}$ were identified and an $\alpha$-decay scheme of $^{180}\mathrm{Tl}$ was constructed based on an analysis of $\alpha$-$\gamma$ and $\alpha$-$\gamma$-$\gamma$ coincidences. Multipolarities of several $\gamma$-ray transitions deexciting levels in $^{176}\mathrm{Au}$ were determined. Based on the analysis of reduced $\alpha$-decay widths, it was found that all $\alpha$ decays are hindered, which signifies a change of configuration between the parent and all daughter states

De-excitation of the strongly coupled band in 177Au and implications for core intruder configurations in the light Hg isotopes

Excited states in the proton-unbound nuclide 177Au were populated in the 92Mo(88Sr, p2n) reaction and identified using the Jurogam-II and GREAT spectrometers in conjunction with the RITU gas-filled separator at the University of Jyväskylä Accelerator Laboratory. A strongly coupled band and its decay path to the 11/2− α-decaying isomer have been identified using recoil-decay tagging. Comparisons with cranked HartreeFock-Bogoliubov (HFB) calculations based on Skyrme energy functionals suggest that the band has a prolate deformation and is based upon coupling the odd 1h11/2 proton hole to the excited 0+ 2 configuration in the 178Hg core. Although these configurations might be expected to follow the parabolic trend of core Hg(0+2 ) states as a function of neutron number, the electromagnetic decay paths from the strongly coupled band in 177Au are markedly different from those observed in the heavier isotopes above the midshell. This indicates that a significant change in the structure of the underlying A+1Hg core occurs below the neutron midshell

Population of a low-spin positive-parity band from high-spin intruder states in 177Au : The two-state mixing effect

The extremely neutron-deficient isotopes 177,179Au were studied by means of in-beam γ-ray spectroscopy. Specific tagging techniques, α-decay tagging in 177Au and isomer tagging in 179Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2d3/2 and 3s1/2 proton-hole configurations, from the 1i13/2 proton-intruder configuration was observed in 177Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state

Determination of fission barrier height of Fr 210 and Ra 210 via neutron measurement

Fission barrier heights of short-lived nuclei away from line of β stability are not known reliably. Low-energy fission of Fr210 and Ra210, produced by (d,p) and (d,n) transfer reaction on the re-accelerated unstable beam Fr209 was investigated at HIE-ISOLDE. Four Timepix3 pixel detectors were installed on the body of the ACTAR TPC demonstrator chamber. Polyethylene converters were used for the detection of fast neutrons. Since no significant background was observed, it was possible to measure the spatial distribution of emitted neutrons reflecting the fission excitation function. Subsequent simulations employing the results of the talys code and available data on fission fragment distributions allowed to estimate directly the value of the fission barrier height for the neutron-deficient nucleus Fr210. This first direct measurement confirmed the reduction of the fission barrier compared to available theoretical calculations by 15-30%