Geometric cross section

Where u, is the mobile phase velocity at the column outlet, Fg the column volumetric flow rate, and Ag the column cross-sectional area available to the mobile phase. In a packed bed only a fraction of the column geometric cross-sectional area is available to the mobile phase, the rest is occupied by the solid (support) particles. The flow of mobile phase in a packed bed occurs predominantly through the interstitial spaces the mobile phase trapped within the porous particles is largely stagnant (37-40). 

The total cross section for collision with a fast particle is never greater than twice the geometrical cross-sectional area of the nucleus and therefore, fast particle cross-sections are rarely much larger than 10- 4 cm (radii of the heaviest nuclei are about 10- cjjij Hence a cross-section of 10-24 considered as... 

Compare to cross section 3.99 x 10-21 cm2, capturing neutrons acts as if it has a much larger cross section than its geometric cross-section i.e., a direct hit is unnecessary. 

FIGURE 9.28 Size distribution of particle geometric cross section (A) as a function of geometric diameter for a typical rural aerosol (adapted from Hegg et at., f993). 

At energies on either side of 8.8 eV a small aluminum sphere presents a much smaller target to incident photons. At 5 eV, for example, the absorption efficiency of a sphere with x = 0.3 is about 0.1 as far as absorption is concerned, the sphere is much smaller than its geometrical cross-sectional area. The field lines of the Poynting vector, shown in Fig. 12.46, are what are to be... 

Energy between adjacent n states Orbital radius Geometric cross section Dipole moment (nd er nf) Polarizability Radiative lifetime Fine-structure interval... 

Fig. 11.12 Plot of the depopulation cross sections of the Rb n( states by ground state Rb nf( ) (ref. 32) ns (O), nd3/2(x), nd ( ) (ref. 57) np ( ) (ref. 26). The cross sections are plotted vs effective quantum number n. For reference the geometric cross section...

Measurements of electron loss from Na 40d and 30d states were done by MacAdam et al.is using crossed Na and ion beams, an arrangement similar to the one shown in Fig. 13.1. The resulting electron loss cross sections are shown in Fig. 13.7, along with the H+-H n = 47 results of Bayfield and Koch scaled by (40/47)4. The H+-H results exhibit the same v/ve dependence but are a constant factor of about 3.5 larger than the other results. As shown, the cross section for v/ve is twice the geometric cross section. Several theoretical cross sections for electron loss and ionization are also shown in Fig. 13.7.15,19-22 The theoretical ionization curves are the two which have cross sections which increase with velocity at low... 

---