Source : Webster's Revised Unabridged Dictionary (1913)

Captivating \Cap"ti*va`ting\, a.
   Having power to captivate or charm; fascinating; as,
   captivating smiles. -- {Cap"ti*va`ting*ly}, adv.

Source : WordNet®

captivatingly
     adv : in a bewitching manner; "she was bewitchingly beautiful"
           [syn: {bewitchingly}, {enchantingly}, {enthrallingly}]