149145
This instrument , along with a mass spectrometer he developed , was widely used by scientists for electron scattering studies which led to the discovery of enhanced vibrational excitation in nitrogen , and for the study of free radicals .
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Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
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