sentences:  Lithium superoxide
  
  Lithium superoxide (LiO2) is an inorganic compound which has only been isolated in matrix isolation experiments at 15-40 K. It is an unstable free radical that has been analyzed using infrared (IR), Raman, electronic, electron spin resonance, soft X-ray spectroscopies, and a variety of theoretical methods.Experimental studies indicate that the LiO2 molecule contains highly ionic bonds.