Question: What are the solution terms for step potential?
About the article "Quantum mechanics", section "Step potential".

Candidate passages:
42 
The Heaviside step potential mainly serves as an exercise in introductory quantum mechanics, as the solution requires understanding of a variety of quantum mechanical concepts: wavefunction normalization, continuity, incident/reflection/transmission amplitudes, and probabilities.
A similar problem to the one considered appears in the physics of normal-metal superconductor interfaces.
Quasiparticles are scattered at the pair potential which in the simplest model may be assumed to have a step-like shape.
The solution of the Bogoliubov-de Gennes equation resembles that of the discussed Heaviside-step potential.
In the superconductor normal-metal case this gives rise to Andreev reflection. 
In quantum mechanics and scattering theory, the one-dimensional step potential is an idealized system used to model incident, reflected and transmitted matter waves.
The problem consists of solving the time-independent Schrödinger equation for a particle with a step-like potential in one dimension.
Typically, the potential is modelled as a Heaviside step function. 
Anodic stripping voltammetry usually incorporates 4 steps if the working electrode is a mercury film or mercury drop electrode and the solution incorporates stirring.
The solution is stirred during the first two steps at a repeatable rate.
The first step is a cleaning step; in the cleaning step, the potential is held at a more oxidizing potential than the analyte of interest for a period of time in order to fully remove it from the electrode.
In the second step, the potential is held at a lower potential, low enough to reduce the analyte and deposit it on the electrode.
After the second step, the stirring is stopped, and the electrode is kept at the lower potential.
The purpose of this third step is to allow the deposited material to distribute more evenly in the mercury.
If a solid inert electrode is used, this step is unnecessary.
The last step involves raising the working electrode to a higher potential (anodic), and stripping (oxidizing) the analyte.
As the analyte is oxidized, it gives off electrons which are measured as a current.
Stripping analysis is an analytical technique that involves (i) preconcentration of a metal phase onto a solid electrode surface or into Hg (liquid) at negative potentials and (ii) selective oxidation of each metal phase species during an anodic potential sweep.
Stripping analysis has the following properties:  Very sensitive and reproducible (RSD<5%) method for trace metal ion analysis in aqueous media.
Concentration limits of detection for many metals are in the low ppb to high pptrange (S/N=3) and this compares favorably with AAS or ICP analysis.
Field deployable instrumentation that is inexpensive.
Approximately 12-15 metal ions can be analyzed for by this method.
The stripping peak currents and peak widths are a function of the size, coverage and distribution of the metal phase on the electrode surface (Hg or alternate)  
The variation of chemical potential with particle number is most easily expressed in terms relating quantities to their concentrations.
The concentration of a species in a given volume, v, is simply Ni / v, so chemical potential can be defined in terms of concentration rather than particle number.
For species in solution  μi = μistd + RT ln ai where μistd is the potential in a given standard state and ai is the activity of the species in solution.
Activity can be expressed as a product of concentration and an activity coefficient, so if activity coefficients are ignored, chemical potential is proportional to the logarithm of the concentration of the species.
For species in the gaseous state the variation is expressed as  μi = μistd + RT ln fi where fi is the fugacity.
If the ideal gas law applies fugacity is equal to partial pressure and chemical potential is proportional to the logarithm of the partial pressure.