Permittivity of space

Ignored in the above quantum confinement model is the fact that when an electron is excited into the conduction band and a positive hole is left behind in the valence band, the hole and electron are coulombically attracted. The pair can be treated as a well-defined qnasiparticle called an exciton, a hydrogen-like system for which a bulk exciton Bohr radius = tfKeJ nfj.f- can be defined. Here k is the dielectric constant (10.2 for bulk CdSe ) and bq is the permittivity of space (8.854 X 10 The quantity a is a... 

Problem 7.4 (Worked Example) Consider a suspension of silica particles in water for which the Hamaker constant is 10" J and the dielectric constant is = 50. If the surface charge is 0.1 charges/nm, calculate how high the molarity of NaCl must be to induce flocculation. Remember, each surface charge is that of an electron, e = 1.6 x 10" C, the permittivity of space is q = 8.8 x 10 J m , and the Bjerrum length is ib — 58/s nm. Assume a weak... 

The first modification is to simply scale the dielectric permittivity of free space (T( ) by a scale factorD to rn ediate or dam pen thelong range electrostatic interactions. Its value was often set to be between 1.0 and 7H.0, the macroscopic value for water. A value of D=2..5, so that u=2..5Ug, wasoften used in early CIIARMM calculation s. 

C = Q/V. In a vacuum, the charge density on the surfaces of the conductors is affected by the permittivity of free space, q. When a dielectric material is placed between the conductors, the capacitance increases because of the higher permittivity, e, of the material. The ratio of e and q gives the dielectric constant, K, of the material, k = e/eg The dielectric constant of siHca glass is 3.8. 

Here o is a fundamental constant called the permittivity of free space. To three deeitnal places,... 

The symbol ao is the first Bohr radius, approximately 52.9 pm, and to is the permittivity of free space.) As we will see in later chapters, Gaussian orbitals are... 

Notice that I have been very careful to use the symbol cq for the permittivity of free space and the symbol s to denote an energy.)... 

Here e° is the permittivity of free space, e the electronic charge, and e the solvent s dielectric constant. Substituting, one may write... 

---