8649
Positrons implanted into the film are trapped by the SO ( 3 ) H clusters , annihilating with the electrons of oxygen and exhibit the high S parameter .
 SO ( 3 ) H, oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 SO ( 3 ) H, oxygen