16876
We performed fluorescence ( FL ) and fluorescence excitation ( FLE ) spectroscopy on the model molecule perylene - 3 , 4 , 9 , 10 - tetracarboxyl acid dianhydride ( PTCDA ) for very low coverages ( below 1 % of a monolayer ) on thin ( 100 ) oriented KCl films .
 Chemical: perylene - 3 , 4 , 9 , 10 - tetracarboxyl acid dianhydride; Chemical: PTCDA; Chemical: KCl
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
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Answer:
 Chemical: perylene - 3 , 4 , 9 , 10 - tetracarboxyl acid dianhydride; Chemical: PTCDA; Chemical: KCl