20865
Two - dimensional penning ionization electron spectroscopy of open - shell metallocenes : outer valence ionic States of vanadocene and nickelocene .
 Chemical: metallocenes; Chemical: vanadocene; Chemical: nickelocene
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: metallocenes; Chemical: vanadocene; Chemical: nickelocene