Sentence:  However, even if it were possible to supply benzophenone with radiation of the appropriate wavelength to produce the second excited <WSD>singlet</WSD> state of the molecule, this <WSD>singlet</WSD> would rapidly convert to the lowest <WSD>singlet</WSD> state (S1). 
Meaning of the word marked with <WSD> tags:  A quantum state having zero spin.