16877
Two different states of PTCDA molecules can be distinguished in the spectra : an initial state , which is observed directly after deposition of the molecules onto the cold sample at 20 K , and a final state , which is found after intensive optical excitation or thermal annealing of the sample .
 Chemical: PTCDA
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: PTCDA