2030
C. S. TUMOSA, J. B. NICHOLAS, AND H. J. ACHE
Exchange rates that lie near this value have a complicated but definite effect on the line shape and resolution. The "hybrid" character of the Mossbauer line shape in the room temperature spectrum of biferrocene Fe(II)Fe(III) picrate probably indicates the existence of an intramolecular exchange process taking place at a rate less than lo7 sec-l. At liquid nitrogen temperature, the Boltzmann factor would be sharply reduced, and the resulting rate would be too small to effect the RIossbauer spectrum appreciably. However, this explanation must be regarded as tentative since other factors in addition to nuclear state lifetimes can also effect the line shapes. If there is a reduction in the electrontransfer rate from 1O1O sec-' in fluid media to
