Deuterium (2H) and Nitrogen 14 (14N) NMR spectroscopy were used to investigate the molecular dynamics in one thermotropic and one lyotropic liquid crystal. Quantitative analyses of deuterium spectral densities of motion for three deuteron sites (ring and C-alpha) at two different Larmor frequencies (46 and 61.4MHz) are reported in the smectic A and C* phases of (S)-[4-(2-methylbutyl)phenyl]-4’-octylbiphenyl carboxylate (8BEF5-d15), a partially deuterated smectogen. 2H spectral densities for two deuteron sites on the chain (C1 and C2/C3) at Larmor frequency 61.4MHz and 14N spectral densities for the head group (NH4+) of the molecule decylammonium chloride (DACl) at 28.9MHz are reported in the lamellar phase of a partially deuterated sample, DACl-d11/H2O binary system. The motional model is the small step rotational diffusion for reorientations plus internal rotations in the strong collision limit. In the chiral C* phase of the first molecule, 8BEF5-d15, the helical axes are aligned along the external magnetic field and the deuteron spins appear to relax in a macroscopically uniaxial environment. After including the molecular tilt, the reorientation processes in the SmC* phase are found to have higher activation energies than those in the smectic A phase. Applying the same motional models to the lyotropic molecule DACl-d11, the tumbling motion of the long axis of the molecule in the aggregates is more rigorous in comparison to the molecular spinning motion. The similarity of deuterium spectral densities from the C1 and C2/C3 sites may indicate a relatively rigid unit of C1-C2-C3-C4 in the backbone. / February 2005

Deuterium (2H) and Nitrogen 14 (14N) NMR spectroscopy were used to investigate the molecular dynamics in one thermotropic and one lyotropic liquid crystal. Quantitative analyses of deuterium spectral densities of motion for three deuteron sites (ring and C[alpha]) at two different Larmor frequencies (46 and 61.4MHz) are reported in the smectic A and C* phases of (S)-[4-(2-methylbutyl)phenyl]-4’-octylbiphenyl carboxylate (8BEF5-d15), a partially deuterated smectogen. 2H spectral densities for two deuteron sites on the chain (C1 and C2/C3) at Larmor frequency 61.4MHz and 14N spectral densities for the head group (NH4+) of the molecule decylammonium chloride (DACl) at 28.9MHz are reported in the lamellar phase of a partially deuterated sample, DACl-d11/H2O binary system. The motional model is the small step rotational diffusion for reorientations plus internal rotations in the strong collision limit. In the chiral C* phase of the first molecule, 8BEF5-d15, the helical axes are aligned along the external magnetic field and the deuteron spins appear to relax in a macroscopically uniaxial environment. After including the molecular tilt, the reorientation processes in the SmC* phase are found to have higher activation energies than those in the smectic A phase. Applying the same motional models to the lyotropic molecule DACl-d11, the tumbling motion of the long axis of the molecule in the aggregates is more rigorous in comparison to the molecular spinning motion. The similarity of deuterium spectral densities from the C1 and C2/C3 sites may indicate a relatively rigid unit of C1-C2-C3-C4 in the backbone.

Deuterium (2H) and Nitrogen 14 (14N) NMR spectroscopy were used to investigate the molecular dynamics in one thermotropic and one lyotropic liquid crystal. Quantitative analyses of deuterium spectral densities of motion for three deuteron sites (ring and C[alpha]) at two different Larmor frequencies (46 and 61.4MHz) are reported in the smectic A and C* phases of (S)-[4-(2-methylbutyl)phenyl]-4’-octylbiphenyl carboxylate (8BEF5-d15), a partially deuterated smectogen. 2H spectral densities for two deuteron sites on the chain (C1 and C2/C3) at Larmor frequency 61.4MHz and 14N spectral densities for the head group (NH4+) of the molecule decylammonium chloride (DACl) at 28.9MHz are reported in the lamellar phase of a partially deuterated sample, DACl-d11/H2O binary system. The motional model is the small step rotational diffusion for reorientations plus internal rotations in the strong collision limit. In the chiral C* phase of the first molecule, 8BEF5-d15, the helical axes are aligned along the external magnetic field and the deuteron spins appear to relax in a macroscopically uniaxial environment. After including the molecular tilt, the reorientation processes in the SmC* phase are found to have higher activation energies than those in the smectic A phase. Applying the same motional models to the lyotropic molecule DACl-d11, the tumbling motion of the long axis of the molecule in the aggregates is more rigorous in comparison to the molecular spinning motion. The similarity of deuterium spectral densities from the C1 and C2/C3 sites may indicate a relatively rigid unit of C1-C2-C3-C4 in the backbone.

Foram medidas as perdas de ernergia de íons 14N e 16O em sólidos (Si,Ti,V,Cu,Zn, Zr e Pd) na faixa de energias de 1 MeV/uma. A técnica utilizada constitui-se na medida de energia de projéteis espalhados a 25° por um alvo delgado de Au, antes e depois de atravessar a folha do element freador. Os resultados experimentais são comparados com as previsões semi-empíricas de Northcliffe & Schilling (N&S), Ziegler e uma nova versão de N&S feita por Hubert e colaboradores, sendo observada uma razoável concordância entre os valores medidos e as curvas semi-empíricas. / Energy loss has been measured 14N and 16O at energies of 1 MeV/amu to 4 MeV/amu in Si, Ti, V, Cu, Zn, Zr and Pd foils. The technique consists in the measurement of the energies of ions scattered through 25 ° by a goldfoil before and after passing through the stopping foil. Our data compared to the semiempirical tabulations of Northcliffe and Schilling (N&S), Ziegler and new version of N&S by Hubert et al.. The predictions of these semiempirical compilations are in reasonable agreement with our experimental data.

Foram medidas as perdas de ernergia de íons 14N e 16O em sólidos (Si,Ti,V,Cu,Zn, Zr e Pd) na faixa de energias de 1 MeV/uma. A técnica utilizada constitui-se na medida de energia de projéteis espalhados a 25° por um alvo delgado de Au, antes e depois de atravessar a folha do element freador. Os resultados experimentais são comparados com as previsões semi-empíricas de Northcliffe & Schilling (N&S), Ziegler e uma nova versão de N&S feita por Hubert e colaboradores, sendo observada uma razoável concordância entre os valores medidos e as curvas semi-empíricas. / Energy loss has been measured 14N and 16O at energies of 1 MeV/amu to 4 MeV/amu in Si, Ti, V, Cu, Zn, Zr and Pd foils. The technique consists in the measurement of the energies of ions scattered through 25 ° by a goldfoil before and after passing through the stopping foil. Our data compared to the semiempirical tabulations of Northcliffe and Schilling (N&S), Ziegler and new version of N&S by Hubert et al.. The predictions of these semiempirical compilations are in reasonable agreement with our experimental data.

The CNO cycle consists of a set of nuclear reactions that convert hydrogen into helium and releases energy in stars. The cycle contributes less than 1% to our Sun's luminosity, but it is responsible for detectable neutrino fluxes that can bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision. The 14N(p,γ)15O is the slowest reaction in the CNO cycle and estabilishes its rate. The experimental study has been performed both at the LUNA 400 kV accelerator deep underground in the Gran Sasso mountain in Italy and at a 3 MV Tandetron in the Helmholtz-Zentrum Dresden-Rossendorf. A proton beam was sent on solid TiN targets and the prompt photons were collected by a composite HPGe detector (at LUNA) or by up to four HPGe detectors (Dresden). The obtained results improve the fit of the excitation function in the R-matrix framework, that is used to extrapolate the S-factor at the very low astrophysical energies. In addition, the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12C reaction were measured, improving the precision for hydrogen depth profiling.

The CNO cycle consists of a set of nuclear reactions that convert hydrogen into helium and releases energy in stars. The cycle contributes less than 1% to our Sun's luminosity, but it is responsible for detectable neutrino fluxes that can bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision. The 14N(p,γ)15O is the slowest reaction in the CNO cycle and estabilishes its rate. The experimental study has been performed both at the LUNA 400 kV accelerator deep underground in the Gran Sasso mountain in Italy and at a 3 MV Tandetron in the Helmholtz-Zentrum Dresden-Rossendorf. A proton beam was sent on solid TiN targets and the prompt photons were collected by a composite HPGe detector (at LUNA) or by up to four HPGe detectors (Dresden). The obtained results improve the fit of the excitation function in the R-matrix framework, that is used to extrapolate the S-factor at the very low astrophysical energies. In addition, the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12C reaction were measured, improving the precision for hydrogen depth profiling.

The thesis deals with RF spectroscopic methods, which are applicable for the detection of hazardous substances such as explosives or drugs. Particular attention is focused on promising method of nuclear quadrupole resonance. Abroad this method has recently been applied in the detection of energetic materials in hazardous locations. The cornerstone of the nuclear quadrupole resonance is to evaluate the interaction between electromagnetic radiation, in the range of medium to very short waves, and the researched substance. Observed parameter are the resonant frequencies of the substance. Spectral analysis of signal is used for their evaluation. Resonant frequencies are always typical for the crystalline structure, therefore every explosive or drug is clearly identifiable by this method.