7382
Because of strong many - electron interaction effects , the detailed dependence of the optical oscillator strength f ( s ) of excitons on nanotube diameter d , chiral angle theta , and electronic subband index P ( the so - called family behavior ) , however , has been unclear .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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