Thompson scattering constant

UCd. This cubic compound orders (antiferro-) magnetically around 5K. The spin structure is not known. Neutron scattering is difficult (because of the high absorption by Cd) and only an upper limit of 1.5/tb for the U ordered moment could be given (Thompson et al, 1988). Specific heat and susceptibility data (Fisk et al. 1984) established UCdn as a moderate HF material (the Sommerfeld constant, for example, is 0.25 J/(molK )) within the regime of magnetic order. 

The elastic scattering intensity produced by an isolated electron was derived by Thompson. The amplitude of the wave elastically scattered by each electron has a well-defined phase relation with the amplimde of the incident wave, thus making interference effects possible. The scattering intensity produced by one electron per imit solid detection angle, 7, is a function of the scattering angle e but it can be considered constant at small angles, i.e., F e)= krf, where Jq is the intensity of the direct beam and is the classical... 

The factor kr is temperature-independenL The non-radiative rate constant contains contributions from a temperature-independent term, which accounts for the deactivation to the ground state, and a temperature-dependent term which can play a role when upper-lying short-lived excited states are thermally accessible (Thompson et al., 2002). Determination of quantum yields is not an easy task. The measurement of absolute quantum yields is critical and requires special equipment, because it is necessaiy to know the amount of excited light received by the sample. These measurements are done by the use of scattering agents and integrating spheres to calibrate the system. For routine woik, one is often satisfied with the determination of relative quantum yields. In this case the quantum yield of the unknown is compared with that of a reference sample ... 

---