Element profile, nuclear reaction

This method is of course restricted to nuclei which provide a satisfactory resonance, usually with a (p,Y) or (p,a) reaction. These are most often found in the region of elements between Z = 10 and Z = 28, although a few examples exist for lighter elements. Unfortunately above Ni there are no nuclear reaction techniques which have proved satisfactory for profiling purposes. 

Nuclear reaction analysis (NRA). Based on the detection of charged particles emitted during nuclear reaction, NRA can be considered as an inelastic counterpart of RBS. NRA is useful in the reverse case as for RBS, namely the depth profiling light elements in a sample composed of heavy elements, (e.g. corroded layers on metallic samples containing O, C, and N). Incident ions are protons ( H) or deuterons (2H). 

Megaelectron volt (MeV) ion beam techniques offer a number of non-destructive analysis methods that allow to measure depth profiles of elemental concentrations in material surfaces. Elements are identified by elastic scattering, by specific nuclear reaction products or by emission of characteristic X-rays. With nuclear microprobes raster images of the material composition at the surface can be obtained. Particle-induced gamma-ray emission (PIGE) is especially suited for fluorine detection down to the ppm concentration level. 

An important advance in understanding in detail the role of hydrogen during hydrolysis has been the use of ion-beam techniques, and particularly resonant nuclear reactions (RNR), which allow direct depth profiling of important elements such as H, Na, Al, and O. For instance, using RNR, Petit et al. (1987) and Schott and Petit (1987) have shown for the first time that pyroxene, olivine, and feldspar surfaces become protonated and/or hydrated to depths of several hundred angstroms during hydrolysis. 

NDP is a prompt nuclear analysis technique, which employs a nuclear reaction that results in emission of charged particles with a specific kinetic energy. It is one of the most powerful non-destructive techniques for depth profiling of some light elements especially for and Li, which have very high thermal neutron capture cross-sections of 3837 and 940 barn respectively. 

A wide range of other nuclear reactions have been used in material science for the depth-profiling analysis of a number of different elements, some of which are tabulated by Feldman and Mayer (1986). Whether these techniques will in the future prove useful for polymers remains to be seen. 

Nuclear reaction analysis (NRA) and elastic recoil detection (ERD) are part of the suit of ion beam analysis (IBA) techniques. They are commonly used for the elemental depth profiling of materials in a wide range of fields, e.g., from biological and medical to the semiconductor industry. 

Tables 1 and 2 show some of the recently used non-resonant and resonant nuclear reactions, respectively. In general these reactions are used to depth profile the element of interest but can also be used to determine the concentration of a particular element in a sample. The following sections describe some of the many applications of NRA and ERD.

Landry F and Schaff P (2001) Simulation and deconvolution program WinRNRA for depth profiling of light elements via nuclear resonance reactions. Nuclear Instruments and Methods in Physics Research B 179 262-266. 

The most commonly used accelerator-based techniques for depth profiling are Rutherford Backscattering (RBS) which will be discussed in Chap. 2, Elastic Recoil Detection (ERD) which will be discussed in Chap. 3, and Nuclear Reaction Analysis (NRA) which will be discussed in Chap. 7. PIXE analysis has the advantage of a very good sensitivity and possible simultaneous detection of all heavier elements. 

In the analysis of light elements by PIGE, the reactions by Coulomb excitation (p, p y) are common. The resonance nuclear reactions (p, y), (p, ay) are used occasionally for the depth-profile. 

Nuclear reaction analysis has mostly been applied to problems in material science, where the use of isotopically enriched compounds allows the profile of a specific element to be targeted by ion beam reactions with its isotopes. For example, in the thermal oxidation of silicon, the growth kinetics and diffusion of oxygen across the Si/Si02 interface region has been studied using sequential oxidations in natural and 0 enriched oxygen gas. The differentiation between possible pathways is due to the isotopic specificity of the NRA technique. 

NRA technique has been used to characterize the obsidian samples from different mineral sites in Mexico by Murillo et al. (1998) who have determined the oxygen concentration by means of the 0(d, p) 0 reaction. To determine the structure and composition of the patina through the depth profiles of the constituent elements like C, N, O, the (d, p) nuclear reactions have been employed using the external beam NRA measurements on copper alloys of archaelogical significance with 3MeV protons and 2MeV deuterons by loannidou et al. (2000). 

When people hear the word nuclear, they think first of bombs and power reactors. Both have profoundly affected our world, for good or ill, since the 1940s. Yet behind these high-profile applications of nuclear technology are hundreds of other uses that have received less attention because they operate on a smaller scale and are clearly beneficial. Many of these involve radioisotopes - variants of common elements produced by nuclear reactions. Radioisotopes have been put to dozens of uses that have improved agriculture and made industry more efficient. Their most significant applications, however, have been in medicine, where they have performed wonders in the prevention, diagnosis and treatment of disease. 

NRA gives information about the depth distribution of elements where a nuclear reaction can occur. One reaction often used for the profiling of hydrogen is N ( j, ay)C - at a resonance energy of 6..38S MeV (97]. The detection limit for the ub.solule elemental concentration is 0.1 to I at. %. In special cases the detection limit can be extended to lower concentratioas using standards of known composition. The detection limit for hydrogen using trace analysis techniques is currently 10 ppma (98). 

Nondestructive depth profiling, which includes angle-resolved measurements, Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), peak intensity measurements from two or more peaks from the same element, and elemental intensity measurements as a function of incident electron energy (3)... 

Neutron depth profiling technique (NDP) [13]. NDP is a speeial method for depth profiling of few light elements, namely He, Li, B and N in any solid material. The method makes use of speeifie nuelear reaetions of these elements with thermal neutrons. The samples are plaeed in the neutron beam from nuclear reactor and the charged products of the neutron indueed reactions (protons or alpha particles) are registered using a standard multiehannel spectrometer. From the measured energy spectra the depth profiles of above mentioned elements can be deduced by a simple computational procedure. 

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