. Biophysical research methods. Biophysics -- Research. 466 JOHN W. G O W E N eigy. The average length of these recoil electron paths is short com- pared to that of a photoelectron from a quantum of the same original energy; a recoil electron, for instance, from a 50 quantum has an average energy of onl,y 11 Recoil electrons are visualized as distributing the energy obtained from high voltage quanta to many discrete spots in the absorbing tissue, in a manner similar to that of photoelectrons with the same amount of energy. Quanta with 100 energy have about 72% of their total
. Biophysical research methods. Biophysics -- Research. 466 JOHN W. G O W E N eigy. The average length of these recoil electron paths is short com- pared to that of a photoelectron from a quantum of the same original energy; a recoil electron, for instance, from a 50 quantum has an average energy of onl,y 11 Recoil electrons are visualized as distributing the energy obtained from high voltage quanta to many discrete spots in the absorbing tissue, in a manner similar to that of photoelectrons with the same amount of energy. Quanta with 100 energy have about 72% of their total energy dissipated as recoil electrons, the mean electron energy being about 17 With 1000 quanta, onlj^ recoil electrons are formed; their average energy UNMODIFIED SCATTERED COMPTON X RAYS SCATTERED PHOTON. CHARACTERISTIC X RAYS INCIDENT PHOTON '//^ UNABSORBED PRIMARY X RAYS HEAT PHOTOELECTROMS RECOIL ELECTRON Fig. G. Sketch to indicate multiple mechanisms of en- ergy dissipation from an X-i'ay beam traversing tissue. is about 435 The recoil electrons, except for directional charac- teristics, behave essentially as photoelectrons in that their energy is dissipated by creating secondary electrons of still lower energy and by creating ion pairs along their path. The degradation scheme of X-ray energy is graphically represented in Figure 6. The conversion of the energy of large quanta into recoil electrons rather than photoelectrons obviously could result in a very great dif- ference in the observed effects of the X rays. For example, a theoret- ical basis for wavelength effects in biological investigations will tend to disappear. Work of Packard (43) on Drosophila eggs gave experi- mental support to this viewpoint since he was unable to detect any differential quantitative effect from the various wavelengths of X rays used. Wyckoff (52) observed that colon bacteria were killed by X-ray. Please note that these images are extracted from scanned page images that ma
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