Sec. 7.12) RADIOACTIVITY 185 



ship of Holloway and Livingston was used. The methods used for the deter- 

 mination of the energy of the particles (alpha and beta) are described in each 

 case with the aid of the following symbols: 



abs. = absorption 



cl. ch. = cloud chamber (with magnetic field in case of beta particles) 



spect. = magnetic deflection (magnetic spectrograph or spectrometer or 

 counter with magnetic field) 



calor. = calorimetric measurements 



ion. ch. = measurement of pulse sizes in ionization chamber or propor- 

 tional counter 



coincid. abs. = beta- and gamma-coincidence counters with absorbers 



coincid. = beta- and gamma-coincidence counters (for information on 

 decay scheme — data not necessarily used in the table) 



spect. coincid. = coincidence counters arranged with a magnetic field 



The alpha-particle energies listed, where more than a single group exists in 

 high abundance, include the group of highest 'energy and those groups with 

 abundance greater than 10 per cent. Conversion electron energies are listed 

 only when it is not known in which shell internal conversion takes place or 

 when no attempt was made to relate the electrons with observed or unob- 

 servable gamma rays; in all other cases entries are made in the column for 

 gamma rays. 



The symbols used to describe the methods employed for the determination 

 of gamma-ray energies have the following meaning: 



abs. = absorption 



cl. ch. recoil = secondary electrons in cloud chamber with magnetic field 

 cl. ch. pair = positron-electron pairs in cloud chamber with magnetic field 

 coincid. abs. = secondary electrons with coincidence counters and absorbers 

 spect. conv. = internal-conversion electrons with magnetic spectrograph 



or spectrometer 

 spect. = secondary electrons with magnetic spectrograph or spectrometer 

 cryst. spect. = direct measurement of gamma-ray energy by diffraction 



in a crystal 

 abs. of e~ = absorption of internal-conversion electrons 

 abs. sec. e~~ = absorption of secondary electrons; 

 coincid. = measurements with gamma-gamma-coincidence counters (for 



information on decay scheme — data not necessarily used in the table) 

 Be-y-n reaction = measurement of neutron energy from Be-y-n reaction 

 D-y-n reaction = measurement of neutron energy from D-y-n reaction 



When internal-conversion electrons are emitted, the energy listed in this 

 column is always that of the corresponding gamma-ray transition. Only 



