Concentration versus depth profiles

NRA is a powerful method of obtaining concentration versus depth profiles of labelled polymer chains in films up to several microns thick with a spatial resolution of down to a few nanometres. This involves the detection of gamma rays produced by irradiation by energetic ions to induce a resonant nuclear reaction at various depths in the sample. In order to avoid permanent radioactivity in the specimen, the energy of the projectile is maintained at a relatively low value. Due to the large coulomb barrier around heavy nuclei, only light nuclei may be easily identified (atomic mass < 30). 

Straightforward to accomplish highly doped n -layers (>10 ° cm ) and this issue requires further attention. Moreover, in this context it should also be emphasized that not until recently viable techniques for measuring electrical carrier concentration-versus-depth profiles in the range cm have... 

The interpretation of pore-water concentration versus depth profiles of O2 and NO in oxic sediments is based on a one-dimensional, steady-state model in which the production or consumption of a solute in a sedimentary layer is balanced by transport into or out of the layer by solute diffusion and burial advection. In mathematical form. 

These dissolved constituents of seawater have concentration versus depth profiles characterized by surface water depletion and deep water enrichment caused by plant consumption in the euphotic zone and release at depth when the biological material dies, sinks and degrades. Examples of these elements are nutrients required for ph5d oplankton growth (P, NO3 and HCO3), oxygen consumed during... 

Figure 1. Concentration versus depth profiles of dissolved Zn (<0.45 pm) in the water column of Lake Greifen on two days during summer stagnation, in comparison to depth profiles of the nutrients P and Si.

Fig. 124. Intensity versus time profile obtained in GD-MS analysis of a Cr-Ni multilayer system on Si substrate (a) discharge current and (b) single-ion monitoring profiles of A Si, B Cr and C Ni (I), and concentration versus depth profile calculated from measurements (II). (Reprinted with permission from Ref. [613]).

In 1972, Ziegler, et al. (p first reported the development of a near-surface technique complimentary to those mentioned above. The technique uses neutron reactions to measure absolute concentration versus depth profiles of a number of the light elements. Neutron... 

Fig. 8.13 Concentration versus depth profiles of organic carbon total sulfur and Fe/Al ratio (mol/g Fe...

Concentration-versus-depth profiles were measured by using neutron activation... 

---