Clustering states in the62Ni(58Ni,58Ni)62Ni reaction

Excitation function and angular distributions of the⁶²Ni(⁵⁸Ni,⁵⁸Ni)⁶²Ni elastic scattering have been measured at incident⁵⁸Ni energies from 220.0 to 230.0 MeV in steps of 0.5 MeV. Evidence of two structures was found in the excitation function; a statistical analysis suggests a possible nuclear cluster quasi-molecular nature for these structures.     

Damped oscillations in the energy autocorrelation functions of the 58Ni+46Ti elastic and 58Ni+62Ni elastic and inelastic scattering cross sections

Structures of non-statistical character, recently observed in ⁵⁸ Ni +⁴⁶ Ti elastic and ⁵⁸ Ni +⁶² Ni elastic and inelastic excitation functions, produce damped oscillations in the cross section energy autocorrelation functions. The analysis of these damped oscillations in terms of S-matrix spin and parity decoherence indicates, as a possible interpretation, damping of the coherent rotational motion of the intermediate dinuclear system formed in the reaction.     

Preformation probability of ga-clusters in rare earth nuclei measured by means of the (p, α) reaction

The results of experimental measurements of (p, α) reactions on nuclei in the rare earth region are reported. It is shown that the dominant acting mechanism is precompound emission. From the absolute cross-section value fitting, the α-preformation probability in the target nucleus can be evaluated. Its values are very close to the ones extracted from (n, α) analysis in the same mass region.     

XRF analysis without sampling of Etruscan depurata pottery for provenance classification

In order to settle the provenance of a set of ancient ceramic shards, the elemental composition data acquired are usually treated by multivariate analysis techniques. The quantitative X‐ray fluorescence (XRF) analysis is an appropriate tool if it is possible to grind ceramics and analyze a sample that is representative of the object. If we deal particularly with well‐preserved objects, we are often not allowed to sample them. Moreover, moving these objects from museum could be unfeasible as well. The aim of this work is to evaluate if spot XRF analysis on integral objects is adequate to classify row clay provenance even if ceramics is not an intrinsically homogeneous material. So, we performed measurements on a set of Etruscan fine ware already classified according to the archaeological, chemical and mineralogical examination. For each sample, several measurement points in polished areas were considered for XRF analyses, allowing a correct provenance classification. Copyright © 2010 John Wiley & Sons, Ltd.     

Enumerating and decoding perfect linear Lee codes

Using group theory approach, we determine all numbers q for which there exists a linear 1-error correcting perfect Lee code of block length n over Z _q , and then we enumerate those codes. At the same time this approach allows us to design a linear time decoding algorithm.      

Ta and W determination by selective XRF energy dispersive analysis

X-ray fluorescence energy dispersive analysis is applied for the determination of Ta and W in sintering compounds. The combination of selective excitation and very simple mathematical procedures permits the determination of the concentrations of the two adjacent elements /Ta and W/ even when the sample contains only few per cent of Ta. Other possible applications are shown.     

Measurements of anomalous dispersion in rayleigh scattering of characteristic X-ray fluorescence

Summary When using characteristic fluorescence X-rays or γ-rays of energy under 100 keV to study the Rayleigh scattering of photons from atoms the effect of anomalous dispersion is not in general negligible. On the contrary, it may cause the atomic cross-section values to vary with respect to the tabulated values—usually calculated in nonresonant approximation—of an order of magnitude in the most critical cases. In this work we present experimental results of Rayleigh scattering where this effect is well evident. We used as sources of excitation a radioisotope (²⁴¹Am,E _γ 59.6 keV) and a X-ray tube with a series of different secondary anodes and solid-state detectors to detect the scattered radiation. We reviewed the atomic form factor formalism which describes the phenomenon in a nonrelativistic treatment and we show its strict analogy with QEDS-matrix theory. We obtained numerical values for the cross-sections by using the tabulated values of the photoelectric cross-sections and we made a comparison with the experimental values. The error of the measurements (∼3%) derives from the superposition of the Rayleigh scattering with the characteristic X-ray fluorescence lines. Within the error limits the agreement with the values from the form factor approximation is very satisfactory.

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Riassunto Quando si utilizza la radiazione X di fluorescenza caratteristica o la radiazione γ di energia minore di 100 keV per studiare la diffusione elastica da parte degli atomi (diffusione di Rayleigh), l'effetto della diffusione anomala non è in generale trascurabile. Al contrario, essa può causare variazioni anche di un ordine di grandezza dei valori delle sezioni d'urto atomiche rispetto ai valori tabulati che sono usualmente calcolati nell'approssimazione non risonante. In questo lavoro si presentano i risultati sperimentali di alcune misure di diffusione di Rayleigh nei quali questo effetto è ben evidente. Come sorgenti di radiazione sono stati utilizzati un isotopo radioattivo (²⁴¹Am,E _γ=59.6 keV) e una serie di anodi secondari associati a un tubo X. Per la rivelazione della radiazione X sono stati utilizzati rivelatori a stato solido. Si è eseguita una revisione del formalismo dei fattori di forma atomici per la descrizione del fenomeno in una trattazione non relativistica e si mostra la stretta analogia con la teoria della matriceS dell'elettrodinamica quantistica. Si sono ottenuti i risultati numerici per le sezioni d'urto di diffusione elastica utilizzando i valori tabulati per le sezioni d'urto fotoelettriche e si sono confrontati con i valori ottenuti sperimentalmente. L'errore delle misure (∼3%) deriva dalla sovrapposizione della diffusione di Rayleigh con le righe di fluorescenza caratteristica. Entro questi limiti di errore l'accordo con i valori ricavati nell'approssimazione dei fattori di forma è molto soddisfacente.

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Резюме При использовании характеристической рентгеновской или γ-лучевой флуоресценции с энергией до 100 кэВ для исследования рэлеевского рассеяния фотонов на атомах, влияние аномальной дисперсии не является в общем случае пренебрежимо малым. Наоборот, эффект аномальной дисперсии может изменить значения атомных поперечных сечений по сравнению с табулированными значениями, обычно вычисляемыми в нерезонансном приближении, в наиболее критических случаях на порядок величины. В этой работе приводятся резулятаты для рэлеевского рассеяния, где эффект аномальной дисперсии является существенным. Мы используем в качестве источников возбуждения радиоизотоп (²⁴¹Am,E _γ=59.6 кэВ) и рентгеновскую трубку с различными вторичными анодами и твердотельные детекторы для регистрации рассеянного излучения. Мы используем формализм атомного форм-фактора, который описывает явление в нерелятивистском приближении. Мы отмечаем точную аналогию с теориейS-матрицы в квантовой электродинамике. Получаются численные значения для поперечных сечений, используя табулированные величины для фотоэлектрических поперечных сечений. Проводится сравнение полученных значений с экспериментальными данными. Погрешность измерений (∼3%) определяется из суперпозиции рэлеевского рассеяния с линиями характеристической рентгеновской Флуоресценции. В пределах погрешностей получается удовлетворительное согласие с результатами, полученными из приближения атомного форм-фактора.

     

Cellulose-based fiber spinning processes using ionic liquids

Cellulose - Cellulose, a natural, renewable, and environment friendly biopolymer, has been considered as a sustainable feedstock in the near future. However, only 0.3% of cellulose is today...