Absorption crossection

The direction of the potential shift of the surface C-N band is the same as for the C-O band on Pt and the shift rates are ca. 30 cm 1/V for Ag and Au (22,23,25) and ca. 45 cm-1/V for Cu (33). The measurement for copper is less accurate due to formation of ion complexes with large absorption crossections and the relatively weak signal from the surface species itself. 

The thermal neutron absorption crossection for Zr is 0.18 x 10 "28m ( ) while the scatter crossection is 8 x 10"28ma. Naturally occuring Hf has an absorption crossection for thermal (0jp253 ev) neutrons of 105 x 10 38ms, the... 

The displacement of the negative absorbance change to the red of the ground-state absorbance peak indicates that there is significant excited state absorption in BChl-a. The excited-state absorption crossection can be calculated according to Eqt n.l,... 

FIG.3 BChl in methanol (A) absorption crossection (B) stimulated emission crossection (C) invertedf normalized 100 ps transient absorbance spectrum. 

Increase in temperature causes a change in the index of refraction. Hence, a transient thermal lens is formed in the volume element absorbing the radiation. The temperature rise is typically of the order of lO C within a volume element of less than 10" cm. Several physical and chemical properties of materials such as thermal diffusivity, optical absorption coefficient, multiphoton crossections quantum yield of photoprocesses etc... may be determined by monitoring the time dependence of the amplitude of the thermal lens. This technique is fast, precise and contactless. 

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