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[en] The hyperfine structure of the 4d²D_3/2,5/2 levels of ^69,71Ga is determined. The 4p²P_3/2->4d²D_3/2 (294.50-nm) and 4p²P_3/2->4d²D_5/2 (294.45-nm) transitions are studied by laser-induced fluorescence in an atomic Ga beam. The hyperfine A constant measured for the 4d²D_5/2 level is 77.3±0.9 MHz for ⁶⁹Ga and 97.9± 0.7 MHz for ⁷¹Ga (3σ errors). The A constant measured for the 4d²D_3/2 level is -36.3±2.2 MHz for ⁶⁹Ga and -46.2±3.8 MHz for ⁷¹Ga. These measurements correct sign errors in the previous determination of these constants. For ⁶⁹Ga the hyperfine B constants measured for the 4d²D_5/2 and the 4d²D_3/2 levels are 5.3±4.1 MHz and 4.6±4.2 MHz, respectively. The isotope shift is determined to be 114±8 MHz for the 4p²P_3/2->4d²D_3/2 transition and 115±7 MHz for the 4p²P_3/2->4d²D_5/2 transition. The lines of ⁷¹Ga are shifted to the blue. This is in agreement with previous measurement. [copyright] 2001 Optical Society of America

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[en] Natural radiative lifetimes and the signs of previously determined hyperfine coupling constants were determined for the 4s₂6p₂Psub(3/2,1/2) levels of gallium. The lifetimes were found to be 167(4) and 172(9) ns, respectively. In addition, the quadrupole moments of ₆₉Ga [0.17(3)b] and ₇₁Ga[0.10(2)b] were deduced, and the isotope shifts in the 639.7 and 641.3 nm Ga lines were determined. (orig.)

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[en] First, the basis and the characteristics of the Czjzek model for the distribution of electric field gradient (EFG) tensor in disordered solids, some of which are still unnoticed, are depicted. That model results from the statistical invariance by rotation of the structure of the considered disordered solid and from the applicability of a central limit theorem to the EFG tensor. These two conditions, which are physically realistic for a wealth of disordered solids, simplify tremendously the derivation of the EFG distribution but at the cost of a complete loss of structural information about the investigated solid. Next, we describe a simple extension of it which is intended to mimic a well-defined local environment, with given values of the asymmetry parameter and of the principal component V_zz of the EFG tensor, perturbed by the disorder of more remote atoms. The effect of disorder is rendered by a Gaussian (Czjzek) noise with an adjustable weight relative to V_zz. The number of free parameters is limited to three, as compared to a sole scale factor for the Czjzek model. Its characteristics are described as a function of the given asymmetry parameter and of the strength of the noise. The aim is to lead to a practical tool which may help to retrieve, as far as possible, the information about the local environment perturbed by disorder from hyperfine measurements and notably from NMR spectra of quadrupolar nuclei. As an example, that extension is applied to some static NMR spectra of ⁷¹Ga in covalent glasses. Calculated static ⁷¹Ga NMR lineshapes are shown as a function of the parameters of the extended model.